Lower Surgical Threshold, Less Patience in Labor for "Obese" Women

Here is yet another study (Ellekjear 2017) showing that labor is often managed differently in "obese" women, with a lower surgical threshold being the most marked finding. The authors concluded:

Caesarean deliveries are undertaken earlier in obese women compared to normal weight women following the onset of active labour, shortening the total duration of active labour.

Research generally shows women of size probably need more time in labor in general, especially in the early stages, but once their labors get going, they usually go well. However, many care providers opt to terminate labor earlier and move quickly to a cesarean. They are understandably concerned about the risks of doing an emergent cesarean on a larger body, but they are usually giving up far too soon and causing an epidemic of "failure to wait" cesareans in women of size. .

There was an infamous Vaginal Birth After Cesarean (VBAC) and obesity study in 2001 that demonstrated this quite strongly. 30 women over 300 lbs. were "allowed" to labor for a VBAC, but only 13% of those who tried for a VBAC ended up with one. As a result, this was widely publicized as a reason not to "let" high-BMI women try for a VBAC and cited by doctors as a reason to deny fat women the opportunity to VBAC.

However, what the full text of the study actually reveals is that the majority of these women were induced, which is known to increase the chances of cesarean and lower the chances of VBAC. Interestingly, the only women who got a VBAC in this study were the ones who were not induced.

Most tellingly, those who had cesareans had their labors stopped at an average of 4.5 cm of dilation. 4.5 cm barely qualifies for the old definition of active labor, and certainly doesn't fit with the new recommended definition of active labor (6 cm)! In other words, these high BMI women were not given an adequate chance to labor.

High induction rates and a lack of patience in labor are the main factors that drive the high cesarean rate in obese women. 

Studies have shown that about half of high BMI women in general are induced, typically increasing cesarean rates. However, when allowed to go into spontaneous labor, cesarean rates are more equalized among BMI groups.

One earlier study found that high BMI women tended to take longer to progress in labor, especially between 4 and 7 cm of dilation. They urged far more patience in the labors of heavier patients.

Similarly, a 2016 study found that 57% of labors in high BMI first-time mothers were stopped before 6 cm of dilation; those mothers ended with cesareans. Failure to Wait is a major problem when doctors attend women of size.

More spontaneous labor and more time during labor would probably have yielded far better VBAC rates in that 2001 VBAC study. It should be pointed out that a look at some later studies showed VBAC rates around 50-70% in obese women, which could almost certainly be increased even more since they also reflect very high induction rates and the old active labor definition. Indeed, research from England shows that the majority of even very high BMI women can have a vaginal birth with different management.

The bottom line is that multiple studies have found that the labors of high BMI women are managed differently than the labors of average-sized women. 

In particular, too many inductions are being done, the surgical threshold is very low, and more patience is needed during labor. This represents an area that is ripe for change and offers hope for lowering the far-too-high cesarean rate in obese women. 

As the authors of a Canadian study concluded about the management of high BMI women:

Because of the potential morbidities associated with Caesarean section, we must modify our management approaches to allow equal opportunity for a vaginal birth for all women.

Reference

BMC Pregnancy Childbirth. 2017 Jul 12;17(1):222. doi: 10.1186/s12884-017-1413-6. Maternal obesity and its effect on labour duration in nulliparous women: a retrospective observational cohort study. Ellekjaer KL, Bergholt T, Løkkegaard E. PMID: 28701155

...METHODS: Retrospective observational cohort study of 1885 nulliparous women with a single cephalic presentation from 37 0/7 to 42 6/7 weeks of completed gestation and spontaneous or induced labour at Nordsjællands Hospital, University of Copenhagen, Denmark, in 2011 and 2012. Total duration of labour and the first and second stages of labour were compared between early-pregnancy normal-weight (BMI <25 kg/m2), overweight (BMI 25-29.9 kg/m2), and obese (BMI ≥30 kg/m2) women. Proportional hazards and multiple logistic regression models were applied. RESULTS: Early pregnancy BMI classified 1246 (66.1%) women as normal weight, 350 (18.6%) as overweight and 203 (10.8%) as obese. No difference in the duration of total or first stage of active labour was found for overweight (adjusted HR = 1.01, 95% CI 0.88-1.16) or obese (adjusted HR = 1.07, 95% CI 0.90-1.28) compared to normal weight women. Median active labour duration was 5.83 h for normal weight, 6.08 h for overweight and 5.90 h for obese women. The risk of caesarean delivery increased significantly for overweight and obese compared to normal weight women (odds ratios (OR) 1.62; 95%CI 1.18-2.22 and 1.76; 95%CI 1.20-2.58, respectively). Caesarean deliveries were performed earlier in labour in obese than normal-weight women (HR = 1.80, 95%CI 1.28-2.54). CONCLUSION: BMI had no significant effect on total duration of active labour. Risk of caesarean delivery increased with increasing BMI. Caesarean deliveries are undertaken earlier in obese women compared to normal weight women following the onset of active labour, shortening the total duration of active labour.

Estimating Fetal Weight Increases Cesarean Risk

Image from Wikimedia

One intervention often seen in pregnancies these days is estimation of fetal weight. But does this improve outcomes?

Bigger babies are more at risk for getting stuck, which is called "shoulder dystocia." Although the actual numerical risk for shoulder dystocia with big babies is not very great (and small babies get stuck too), the risk for shoulder dystocia is higher with a bigger baby. Most of the time it is resolved without damage, but in some cases babies or moms are hurt, sometimes seriously. In rare cases, babies even die. Damage from shoulder dystocia is one of the main reasons care providers get sued.

As a result, a big baby make many care providers nervous. So they routinely employ estimation of fetal weight near the end of pregnancy, either by hands-on estimation or by ultrasound estimation. But the critical question is whether estimating fetal weight actually improves outcomes.

Here is yet another study that shows that estimating fetal weight does NOT improve outcomes and that it increases the risk for cesareans. 

In this very large multi-center MFMU study, a baby estimated to be above 4000g (8 lbs., 13 oz.) was more than twice as likely to be born by cesarean. A diabetic mother with a baby estimated to be above 3500g (about 7 lbs. 12 oz.) was more than nine times as likely to have a cesarean.

This relationship persisted even when adjusted for actual birth weight and other variables, showing it was not just about the baby's size. The mere prediction of a large baby (whether baby was actually large or not) increased the risk for cesarean, suggesting that it is the way big babies are managed that makes the difference.

This is a particularly pertinent issue for women of size. Because "obese" women tend to have larger babies on average, care providers can get very anxious about fetal size in their pregnancies. Fear of big baby (and the resulting interventions) is one of the top drivers around the outrageously high cesarean rate in high-BMI women.

Sadly, this study does not directly address the effect of fetal weight estimation in the sub-population of obese women. It would be great to have data actually examining a practice that is so common in the management of obese women.

However, this is a very large and very powerful study showing that the practice of estimating fetal weight is harmful in pregnant women in general.

And it is just the latest in a long series of studies that show that the common practice of estimating fetal weight increases the cesarean rate.

Given that it is such a common practice in obstetrics these days, the practice of estimating fetal size before birth needs to be re-evaluated. 

There are times when estimating fetal size can be appropriate, but most of the time it is more harmful than helpful. Care providers need to stop using it routinely.

And its use especially needs to be evaluated in the management of women of size.


Reference

Obstet Gynecol. 2016 Sep;128(3):487-94. doi: 10.1097/AOG.0000000000001571. Association of Recorded Estimated Fetal Weight and Cesarean Delivery in Attempted Vaginal Delivery at Term. Froehlich RJ1, Sandoval G, Bailit JL, Grobman WA, Reddy UM, Wapner RJ, Varner MW, Thorp JM Jr, Prasad M, Tita AT, Saade G, Sorokin Y,Blackwell SC, Tolosa JE; MSCE, for the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network. PMID: 27500344

OBJECTIVE: To evaluate the association between documentation of estimated fetal weight, and its value, with cesarean delivery. METHODS: This was a secondary analysis of a multicenter observational cohort of 115,502 deliveries from 2008 to 2011. Data were abstracted by trained and certified study personnel. We included women at 37 weeks of gestation or greater attempting vaginal delivery with live, nonanomalous, singleton, vertex fetuses and no history of cesarean delivery. Rates and odds ratios (ORs) were calculated for women with ultrasonography or clinical estimated fetal weight compared with women without documentation of estimated fetal weight. Further subgroup analyses were performed for estimated fetal weight categories (less than 3,500, 3,500-3,999, and 4,000 g or greater) stratified by diabetic status. Multivariable analyses were performed to adjust for important potential confounding variables. RESULTS: We included 64,030 women. Cesarean delivery rates were 18.5% in the ultrasound estimated fetal weight group, 13.4% in the clinical estimated fetal weight group, and 11.7% in the no documented estimated fetal weight group (P<.001). After adjustment (including for birth weight), the adjusted OR of cesarean delivery was 1.44 (95% confidence interval [CI] 1.31-1.58, P<.001) for women with ultrasound estimated fetal weight and 1.08 for clinical estimated fetal weight (95% CI 1.01-1.15, P=.017) compared with women with no documented estimated fetal weight (referent). The highest estimates of fetal weight conveyed the greatest odds of cesarean delivery. When ultrasound estimated fetal weight was 4,000 g or greater, the adjusted OR was 2.15 (95% CI 1.55-2.98, P<.001) in women without diabetes and 9.00 (95% CI 3.65-22.17, P<.001) in women with diabetes compared to those with estimated fetal weight less than 3,500 g. CONCLUSION: In this contemporary cohort of women attempting vaginal delivery at term, documentation of estimated fetal weight (obtained clinically or, particularly, by ultrasonography) was associated with increased odds of cesarean delivery. This relationship was strongest at higher fetal weight estimates, even after controlling for the effects of birth weight and other factors associated with increased cesarean delivery risk.

Most Babies Suspected to be Large Actually Aren't

So many mothers get the "big baby" fear card handed to them during pregnancy. This often leads to pressure for interventions such as induction of labor, or scaring women into a planned cesarean.

In this survey, one-third of women surveyed were told their babies were getting "quite large." Yet only one in five of these women actually went on to have large babies (around 9 lbs. or more).

Although the survey doesn't have information specifically about women of size, I would bet that the rate of big baby fear cards is even higher in our care. There is some justification for this; on average, we do tend to have somewhat larger babies. But even so, most high-BMI women have average-sized babies. And even if they do have a bigger baby, most of these can be born just fine with a little care and patience, especially if they have full mobility during labor.

But the fear of big babies from big mothers is so exaggerated these days that many care providers act as if every high-BMI woman will have a Godzilla Baby. Sadly, a great deal of the increased interventions we experience is likely tied to that fear of big babies.


Reference

Matern Child Health J. 2015 Dec;19(12):2578-86. doi: 10.1007/s10995-015-1776-0. Labor and Delivery Experiences of Mothers with Suspected Large Babies. Cheng ER1, Declercq ER2, Belanoff C3, Stotland NE4, Iverson RE5. PMID: 26140835

OBJECTIVE: To characterize the prevalence of and factors associated with clinicians' prenatal suspicion of a large baby; and to determine whether communicating fetal size concerns to patients was associated with labor and delivery interventions and outcomes. METHODS: We examined data from women without a prior cesarean who responded to Listening to Mothers III, a nationally representative survey of women who had given birth between July 2011 and June 2012 (n = 1960). We estimated the effect of having a suspected large baby (SLB) on the odds of six labor and delivery outcomes. RESULTS: Nearly one-third (31.2%) of women were told by their maternity care providers that their babies might be getting "quite large"; however, only 9.9% delivered a baby weighing ≥4000 g (19.7% among mothers with SLBs, 5.5% without). Women with SLBs had increased adjusted odds of medically-induced labor (AOR 1.9; 95% CI 1.4-2.6), attempted self-induced labor (AOR 1.9; 95% CI 1.4-2.7), and use of epidural analgesics (AOR 2.0; 95% CI 1.4-2.9). No differences were noted for overall cesarean rates, although women with SLBs were more likely to ask for (AOR 4.6; 95% CI 2.8-7.6) and have planned (AOR 1.8; 95% CI 1.0-4.5) cesarean deliveries. These associations were not affected by adjustment for gestational age and birthweight. CONCLUSIONS FOR PRACTICE: Only one in five US women who were told that their babies might be getting quite large actually delivered infants weighing ≥4000 g. However, the suspicion of a large baby was associated with an increase in perinatal interventions, regardless of actual fetal size.

Preventing the First Cesarean: Don't Go to the Hospital Too Early

Dark line with squares is overall cesarean rate,
Light line with triangles is primary cesarean rate,
Line with diamonds that goes up and then plummets is the VBAC rate

As part of Cesarean Awareness Month, we are discussing the long-term implications of a high cesarean rate, as well as how to lower the sky-high cesarean rate in women of size.

One of the important parts of lowering the overall cesarean rate is preventing the first (or "primary") cesarean.

As you can see from the chart, the primary cesarean rate (middle line) has risen over the years pretty much in parallel with the overall cesarean rate, even as the VBAC (Vaginal Birth After Cesarean) rate has drastically declined.

The VBAC rate has declined so strongly because many places have VBAC bans in place. Once a woman has that first cesarean, she usually has repeat cesareans thereafter, unless she is one of the lucky ones who can find a provider that is truly willing to support VBAC.

Thus the first step to lowering the high overall cesarean rate is to prevent the very first cesarean from happening whenever possible.

And one important step in preventing primary cesareans is not going to the hospital too early in labor. 

Research has shown that when women are admitted early in labor ("latent" labor), they have a much greater chance of having a cesarean than if they get to the hospital a bit later, when contractions are consistent and dilation starts to change more quickly ("active" labor).

In fact, a recent consensus statement from the American Congress of Obstetricians and Gynecologists and the Society for Fetal-Maternal Medicine suggests that the definition of "active" labor be changed from 4 cm to 6 cm.

Lamaze International has highlighted this with their related discussions on "Six is the New Four."

This proposed change is based on research that suggests that labor tends to progress more slowly in the early stages of labor than recognized in previous guidelines, and that many "failure to progress" cesareans might be prevented by being just a little bit more patient during labor.

Below is yet another study that confirms the importance of not going into the hospital until labor is well-established and "active."

In this study, more than half the women were admitted during "preactive" labor, and those that were had more than twice the c-section rate of those who were admitted in active labor.

If half of women are regularly being admitted into the hospital during latent labor, this strongly suggests that delaying admission to the hospital until labor is truly in the "active" phase might help lower the primary cesarean rate significantly.

This may be a particularly important consideration for women of size. Some research suggests that "overweight" and "obese" women have longer labors, especially in the stage just before transition. Although no one has actually studied yet whether delaying admission until 6 cm in obese women would lower cesarean rates in that group, it certainly seems like a logical conclusion.

In combination with lowering unnecessary induction rates and being more patient in labor, delaying hospital admission until 6 cm might really help impact the cesarean rate in obese women.

Summary

The take-home message for mothers is that if you plan to birth in the hospital, don't rush to the hospital in early labor.

Obviously, if there is something that is concerning you or doesn't feel right, it's important to be evaluated, and you should not hesitate to go in and ask for evaluation. Certain other medical situations, of course, might also call for early evaluation; your care provider will help you determine the situations to be cautious about.

However, most of the time, there is no need to be in the hospital right away if labor has started. The sooner you go in, the more likely you are to have interventions like oxytocin augmentation and cesareans.

The take-home message for hospitals is to have stricter admissions policies, given that around half of women are being admitted in early labor. The secondary message is to allow more time in labor before moving to a cesarean (barring fetal distress); a "failure to progress" cesarean is too often a "failure to wait" cesarean.

Bottom line: To lower the rate of primary cesareans, wait till labor is well-established before going to the hospital, and practice more patience during labor before moving to a cesarean if all else is well. 


References

J Midwifery Womens Health. 2014 Jan;59(1):28-34. doi: 10.1111/jmwh.12160. Epub 2014 Feb 11. Outcomes of nulliparous women with spontaneous labor onset admitted to hospitals in preactive versus active labor. Neal JL, Lamp JM, Buck JS, Lowe NK, Gillespie SL, Ryan SL. PMID: 24512265

INTRODUCTION: The timing of when a woman is admitted to the hospital for labor care following spontaneous contraction onset may be among the most important decisions that labor attendants make because it can influence care patterns and birth outcomes. The aims of this study were to estimate the percentage of low-risk, nulliparous women at term who are admitted to labor units prior to active labor and to evaluate the effects of the timing of admission (ie, preactive vs active labor) on labor interventions and mode of birth. METHODS: Data from low-risk, nulliparous women with spontaneous labor onset at term gestation were merged from 2 prospective studies conducted at 3 large Midwestern hospitals...RESULTS: Of the sample of 216 low-risk nulliparous women, 114 (52.8%) were admitted in preactive labor and 102 (47.2%) were admitted in active labor. Women who were admitted in preactive labor were more likely to undergo oxytocin augmentation (84.2% and 45.1%, respectively; odds ratio [OR], 6.5; 95% confidence interval [CI], 3.43-12.27) but not amniotomy (55.3% and 61.8%, respectively; OR, 0.8; 95% CI, 0.44-1.32) when compared to women admitted in active labor. The likelihood of cesarean birth was higher for women admitted before active labor onset (15.8% and 6.9%, respectively; OR, 2.6; 95% CI, 1.02-6.37). DISCUSSION: Many low-risk nulliparous women with regular, spontaneous uterine contractions are admitted to labor units before active labor onset, which increases their likelihood of receiving oxytocin and giving birth via cesarean. An evidence-based, standardized approach for labor admission decision making is recommended to decrease inadvertent admissions of women in preactive labor. When active labor cannot be diagnosed with relative certainty, observation before admission to the birthing unit is warranted.

Previous Research on Early Admission in Labor

Midwifery. 2013 Dec;29(12):1297-302. doi: 10.1016/j.midw.2013.05.014. Epub 2013 Jul 24.
Influence of timing of admission in labour and management of labour on method of birth: results from a randomised controlled trial of caseload midwifery (COSMOS trial). Davey MA1, McLachlan HL, Forster D, Flood M. PMID: 23890679

OBJECTIVE: to explore the relationship between the degree to which labour is established on admission to hospital and method of birth...SETTING: a large tertiary-level maternity service in Melbourne, Australia. PARTICIPANTS: English-speaking women with no previous caesarean section at low risk of complications in pregnancy were recruited to a randomised controlled trial. Trial participants whose management did not include a planned caesarean and who were admitted to hospital in spontaneous labour were included in this secondary analysis of trial data (n=1532)... RESULTS: ...Pooling the two randomised groups of nulliparous women, and after adjusting for randomised group, maternal age and maternal body mass index, early admission to hospital was strongly associated with caesarean section. Admission before the cervix was 5 cm dilated increased the odds 2.4-fold (95%CI 1.4, 4.0; p=0.001). Augmentation of labour and use of epidural analgesia were each strongly associated with caesarean section (adjusted odds ratios 3.10 (95%CI 2.1, 4.5) and 5.77 (95%CI 4.0, 8.4) respectively. CONCLUSION: these findings that women allocated to caseload care were admitted to hospital later in labour, and that earlier admission was strongly associated with birth by caesarean section, suggest that remaining at home somewhat longer in labour may be one of the mechanisms by which caseload care was effective in reducing caesarean section in the COSMOS trial.

J Obstet Gynecol Neonatal Nurs. 2003 Mar-Apr;32(2):147-57; discussion 158-60.
Impact of collaborative management and early admission in labor on method of delivery.
Jackson DJ1, Lang JM, Ecker J, Swartz WH, Heeren T. PMID: 12685666

OBJECTIVE: This study compared the effects of early admission in labor and perinatal care provider on delivery method. Higher spontaneous vaginal delivery rates for certified nurse midwives as compared with physicians have been reported in observational studies and randomized clinical trials. Certified nurse midwives, with their more expectant approach to labor management, would be expected to admit women later in labor than obstetricians. METHODS: Prospective cohort study of 2,196 low-risk pregnancies, with singleton, vertex infants admitted in spontaneous labor. Independent and joint effects of perinatal care provider and cervical dilation at admission on delivery method were evaluated... RESULTS: Fewer (23.4%) women in collaborative care were admitted in early labor (< 4 cm cervical dilation) than women managed by obstetricians (95% CI = -27.6 to -19.2). Obstetrician care had 9% to 30% fewer spontaneous vaginal deliveries. Women admitted early in labor also had 6% to 34% fewer spontaneous vaginal deliveries. Evaluation of joint effects suggested that interaction between obstetrician provider and earlier admission increased the risk of operative delivery. CONCLUSION:
Later admission in labor (at 4 cm or greater cervical dilation) and management of perinatal care by certified nurse midwives in collaboration with obstetricians increased the rate of spontaneous vaginal delivery in low-risk women.

Induction Math: The Importance of the Bishop Score

Image from Relay Health, as displayed on http://www.med.umich.edu/

Yet another study shows that inducing labor increases the risk for a cesarean, especially in first-time mothers with an unripe cervix (one that has not done much dilating and effacing yet).

In the study, they specifically looked at cesarean rates among induced mothers with an unripe cervix.  They found that cesarean rates were particularly high among first-time mothers who were induced with an unripe cervix, but the risk was also elevated for mothers with prior vaginal births who were induced on an unripe cervix.  

This is why it is absolutely vital to ask your provider about your Bishop Score before agreeing to induce labor.

The Bishop Score

The Bishop Score is a measure of how soft and ripe your cervix is before labor. It can help predict whether or not your body is ready for labor, and whether or not an induction is likely to succeed or fail.

A vaginal exam is done and the care provider evaluates the degree of:

• cervical dilation (how far the cervix has opened so far)
• cervical effacement (how thinned out the cervical walls are)
• cervical consistency (how soft or firm the cervix is)
• cervical position (whether the cervix is pointing forwards or backwards relative to the vaginal walls)
• fetal station (how far down the baby is in the pelvis)

[If you need further explanation about the terminology above, you can find an excellent explanation and great illustrations here.]

Each factor is "graded" on a scale of 0-2 or 0-3.  The maximum possible score is 13. This all adds up to what some doulas call "induction math".

The exact cut-offs used differs by source, but generally a score of 5 or less indicates the woman is unlikely to go into labor spontaneously at that time, and that an induction is likely to fail (result in a cesarean).

A score of 8 or more indicates that an induction is more likely to succeed.  A score of 9 or more indicates the woman will likely go into labor on her own very soon.

Sometimes care providers use modifications of a Bishop Score to help predict likelihood of successful induction.  One point may be added to the score for the existence of pre-eclampsia or for every previous vaginal birth.  One point is often subtracted for a "postdates" pregnancy, being a first-time mother (or for no previous vaginal births), or preterm prelabor rupture of membranes.

The Bishop Score is just one tool for predicting a woman's response to induction.  Obviously, other factors matter as well.

The Influence of Fetal Position

One often-overlooked factor is fetal position ─ which way a head-down baby is facing in utero.  Most babies face either occiput anterior (back of the head towards mother's belly; baby looking at mother's back) or occiput posterior (back of the head towards mother's back; baby looking at mother's belly).

Often a low Bishop Score is associated with a posterior baby, which is a less ideal position for birth.  In this position, the the baby's head is not putting pressure as efficiently on the cervix, so there is less cervical effacement or dilation, and the cervix is often posterior (pointed towards the lower vaginal wall and hard to reach during a vaginal exam).  When the baby rotates to anterior, the Bishop Score often changes dramatically because the physics of the baby's pressure changes.

Many "overdue" babies are actually posterior babies whose positions are simply not putting the most efficient kind of pressure on the cervix to thin and dilate, and so the body wisely does not go into labor yet.  Forcing the issue by inducing labor when the baby is posterior (or has other malpositions) tends to result in long, hard labors that often end in a c-section.

[This is a pet peeve for me, because it is the story of my first c-section....induced at 40 weeks despite a very low Bishop Score (the OB told me I had a "horrible" cervix) and a malpositioned baby.  Small wonder I ended up with a cesarean!]

So if your Bishop Score is low, it may not just be that your body is not "ripe" for labor, it may also be that the reason you are not ripe is because the baby is not in a great position for labor.  For that reason, it may be wise to delay inducing until the baby is in a more favorable position for labor.

Seeing a pregnancy chiropractor and getting adjusted may help encourage the baby to get into a better position for labor, which in turn might lessen your chances for a cesarean.  (This is what was key for me in my VBACs.)

Induction Triples the Risk for Cesarean in First-Time Mothers

In the 2011 study listed below, the charts of women who were induced with a Bishop score of less than 7 were studied.

Those first-time moms who were induced with a Bishop score less than 7 had a whopping 42% cesarean rate.  

This shows just how important it is to have a nice ripe cervix before inducing labor, and especially so in first-time moms, whose cervices have never dilated before.

Sometimes a doctor will try to reassure you that it doesn't matter if your cervix isn't ripe; they use drugs that help ripen the cervix before starting the induction drugs.  And it's true that these drugs can help at times.

However, even with cervical ripening methods, many inductions still fail.  Cervical ripening drugs are simply not a panacea for preparing the body for birth when it's not ready.  They work best when the baby is in good position and the body is close to being ready but not quite there yet.  Cervical ripening methods are very unlikely to help in women with very low Bishop Scores.

Now, if the cervix has dilated before, induction is more likely to work. Women who had had vaginal births before had a much lower cesarean rate after induction in this study, 14%.  Still, this was nearly double the cesarean rate of those multips who went into labor spontaneously.  

Obviously, cervical ripeness matters, even in women who have had vaginal births before.

Take-Home Points About Induction

Additional research confirms that cervical ripeness is one of the key factors in whether or not an induction will work.  Here are some take-home lessons from the 2011 study:

• Whenever possible, wait to go into labor spontaneously
• If induction is being considered, try to avoid inducing if your Bishop Score is less than 7

Other general bits of wisdom about inductions:

• Try to see a provider who is not induction-happy and won't induce automatically at a certain gestation.  This is especially important for women of size, because many providers induce "obese" women at extremely high rates (a 50-60% induction rate is common in many recent studies).  This is a direct but under-acknowledged factor in the very high cesarean rate in women of size.

• Question whether an induction is truly necessary in your case.  Many inductions are done routinely, simply because it is convenient for the provider or protocol to induce by a certain gestational age.  However, you don't have to agree to this intervention.  Discuss the pros and cons of the induction vs. waiting with the provider, and see if you can negotiate for more time.  

• If you are contemplating an induction, ask about your Bishop Score before agreeing to the induction.  If at all possible, try not to induce before you have a favorable Bishop Score. 

• If you are contemplating induction, ask about your baby's position before agreeing to the induction.   If the baby is not anterior, consider delaying the induction.  Seeing a well-trained pregnancy chiropractor may help encourage the baby to get into an easier position for birth.

• If a medical condition makes induction necessary even with an unripe cervix, look into ways to increase cervical ripeness before the induction.  This can include acupuncture, herbs, and cervical ripening agents.  Consider the pros and cons of each choice carefully for your situation, and remember that gentler methods generally need a longer time to be effective.  Don't wait to the last minute to try the more gentle methods of cervical ripening if you are very likely to face induction.

• Be sure your provider allows adequate induction time before resorting to a cesarean.  Recent research has shown that many providers move to a cesarean too soon in an induction; allowing just a few more hours (provided mother and baby are doing well ) may result in a vaginal birth after all.

• Remember, induction doesn't automatically mean you're going to have a cesarean; many women who are induced do end up having a vaginal birth.  Go in with a positive attitude, try to remain as mobile as possible, and be sure to have professional labor support (a doula), who can often help maximize your chances even during an induction.  However, because an induction does increase the chances for cesarean, be prepared for any possibility and have a cesarean birth plan ready if one becomes necessary.

Induction is more and more common these days.  This is why it is important for all women to be informed birth consumers and learn more about their choices around induction.  The Bishop Score is an important ─ and often overlooked ─ part of this discussion.

*Thanks to Holistic NYC Doula for the term "induction math" and for her excellent posts on the topic of the Bishop Score.



References

Acta Obstet Gynecol Scand. 2011 Oct;90(10):1094-9. doi: 10.1111/j.1600-0412.2011.01213.x. Epub 2011 Jul 21. Induction of labor and the risk for emergency cesarean section in nulliparous and multiparous women. Thorsell M, et al.   PMID: 21679162

OBJECTIVE: To assess the risk for emergency cesarean section among women in whom labor was induced in gestational week ≥41 and to evaluate if parity and mode of induction affected this association.
DESIGN: Hospital-based retrospective cohort study.
POPULATION: Singleton pregnancies delivered after ≥41 gestational weeks at Danderyd Hospital, Stockholm, Sweden, during 2002-2006.
MATERIAL AND METHODS: Of 23 030 singleton pregnancies meeting the entry criteria, 881 were induced with a Bishop score of less than 7. Obstetric outcome was assessed through linkage with the Swedish Medical Birth Registry and a local obstetrical database containing information from patients' medical files. Results were adjusted for body mass index, age and the use of epidural analgesia.
MAIN OUTCOME MEASURE: Risk for emergency cesarean section.
RESULTS: Among women who were induced, the proportions delivered by emergency cesarean section were 42% for nulliparous and 14% for multiparous. Compared to spontaneous onset, this corresponded to a more than threefold increase in risk for nulliparous women (OR 3.34, 95% CI 2.77-4.04) and an almost twofold increase in risk for multiparous women (OR 1.94, 95% CI 1.24-3.02). There was no significant difference in risk for emergency cesarean section between the two methods of induction (PGE(2) and transcervical catheter).
CONCLUSIONS: Compared to spontaneous onset of delivery, induction of labor is associated with an increased risk for emergency cesarean section both among nulliparous and multiparous women. When labor is induced, the high risk for emergency cesarean must be kept in mind.

Clin Obstet Gynecol. 2006 Sep;49(3):564-72. Preinduction cervical assessment. Baacke KA, Edwards RK.   PMID: 16885663 

The rate of labor induction is increasing in the United States. Methods for quantifying cervical factors have been developed to identify patients who may benefit from cervical ripening before induction. The first cervical scoring systems used digital examination. More recently, cervical ultrasound and testing for the presence of fetal fibronectin have been suggested to evaluatecervical readiness for labor induction, but neither of these methods provides a significant improvement over digital examination. The Bishop score, the most widely used digital examination scoring system, still is the most cost effective and accurate method of evaluating the cervix before labor induction.

Obstet Gynecol. 2005 Apr;105(4):690-7. Bishop score and risk of cesarean delivery after induction of labor in nulliparous women. Vrouenraets FP, et al.  PMID: 15802392 

OBJECTIVE: To quantify the risk and risk factors for cesarean delivery associated with medical and elective induction of labor in nulliparous women.
METHODS: A prospective cohort study was performed in nulliparous women at term with vertex singleton gestations who hadlabor induced at 2 obstetrical centers. Medical and elective indications and Bishop scores were recorded before labor induction. Obstetric and neonatal data were analyzed and compared with the results in women with a spontaneous onset of labor. Data were analyzed using univariate and multivariable regression modeling.
RESULTS: A total of 1,389 women were included in the study. The cesarean delivery rate was 12.0% in women with a spontaneous onset of labor (n = 765), 23.4% in women undergoing labor induction for medical reasons (n = 435) (unadjusted odds ratio [OR] 2.24; 95% confidence interval [CI] 1.64-3.06), and 23.8% in women whose labor was electively induced (n = 189) (unadjusted OR 2.29; 95% CI 1.53-3.41). However, after adjusting for the Bishop score at admission, no significant differences in cesarean delivery rates were found among the 3 groups. A Bishop score of 5 or less was a predominant risk factor for a cesarean delivery in all 3 groups (adjusted OR 2.32; 95% CI 1.66-3.25). Other variables with significantly increased risk for cesarean delivery included maternal age of 30 years or older, body mass index of 31 or higher, use of epidural analgesia during the first stage oflabor, and birth weight of 3,500 g or higher. In both induction groups, more newborns required neonatal care, more mothers needed a blood transfusion, and the maternal hospital stay was longer.
CONCLUSION: Compared with spontaneous onset of labor, medical and elective induction of labor in nulliparous women at term with a single fetus in cephalic presentation is associated with an increased risk of cesarean delivery, predominantly related to an unfavorable Bishop score at admission.

News Flash: Labor Managed Differently in High-BMI Women!

For a long time, doctors have observed a higher cesarean rate in high-BMI women, but always blamed this solely on obesity.

But how would obesity impede labor and result in more cesareans, you ask?

The usual reasons given (based on assumptions or poor research) were soft tissue dystocia (i.e., the fat vagina theory), or inefficient uterine contractility due to high leptin or cholesterol levels (seriously, that's a current theory still floating around, despite evidence that contradicts it).

Yet no one was asking whether the way labor was managed in "obese" women contributed to this high cesarean rate.

Now, for the first time, FINALLY someone is starting to ask these questions!  A Canadian study out earlier this year examined labor management of obese women compared with other women.

And guess what?!  As I've been saying for years, they found that the labors of women of size are indeed managed differently, with more interventions and a much lower threshold for surgery. 

Furthermore, when the study controlled for the use of interventions, the relationship between obesity and cesareans was "markedly attenuated." 

Details from the Study

There are a couple of interesting items in the study worth a closer look.

Induction Rates

First, induction rates went up strongly as BMI increased.  Here's a summary of induction rates by BMI category (delivery BMI):

• "Normal" BMI (20-24.9)               23.7% induced
• "Overweight" BMI (25-29.9)         29.3% induced
• "Obese" BMI (30-39.9)                37.2% induced
• "Morbidly Obese" BMI (40+)       50.0% induced

Now, some of that increased rate is to be expected, given that fatter women have higher rates of pre-eclampsia and other complications, and induction is more common in women with these complications.  But even so, a 50% induction rate?  Do 50% of all "morbidly obese" women really need to be induced? Come on!

A great deal of research has shown that induction of labor is linked to higher cesarean rates.  This is particularly true for first-time mothers or women who have never had a vaginal birth before, or whose cervix was not ripe before the induction.

So why don't any researchers (including this one) connect the dots between such an extremely high induction rate in women of size and a resulting high cesarean rate?

The authors don't really comment on the induction rates or question them at all; most research never does.  Most authors assume that all these inductions are truly indicated, especially in women of size.  But frankly, they need to question such a high rate of induction more closely.

How many of these inductions were for real medical indications, and how many were for dubious indications like suspected macrosomia or provider fear? 

We know from research that inducing early for a suspected big baby does not improve outcomes, and actually strongly increases the cesarean rate in many studies.  Yet it is common practice still among clinicians to induce labor early if a big baby is suspected, especially in women of size. 

So when you see the 50% induction rate in "morbidly obese" women, how many were for "soft" indications like suspected macrosomia?  And what was the cesarean rate among those induced for "soft" indications? I would love for researchers to look more carefully at induction indications and how that influences cesarean rates in women of size.

We know from another recently published study that high induction rates definitely do have a strong influence on cesarean rates in obese women.  According to the authors of that study:

We conclude that morbid obesity is associated with a significantly higher risk of pre-existing medical conditions, developing antenatal complications, induction of labour, caesarean section and greater birth weight. However, there was no significant difference in caesarean section rates when adjusted for induction of labour. 

More research is needed to further clarify the impact of high induction rates on cesarean rates in obese women, and researchers need to finally start questioning the validity of many of these inductions.

Cervical Status Upon Admission

Another interesting finding that deserves further investigation is a major difference in cervical status upon admission and what might be influencing this.

Women whose cervix is more dilated upon admission tend to have shorter labors and a lower cesarean rate; those whose cervix is less dilated at admission usually have longer labors and more cesareans because their bodies aren't ready to labor yet. 

In this study, 37.9% of women of average BMI had minimal cervical dilation (2 cm or less) upon admission to the hospital.  In comparison, 55.7% of "morbidly obese" women had minimal cervical dilation upon admission.

Yes, this is surely partly due to a higher rate of inductions and therefore less spontaneous labors in the high-BMI group, but it also suggests that perhaps this group is far less ready for labor when being induced.  Again, many authors have noted this and have blamed it on "inefficient uterine contractility" or hormonal deficits, but what if there are other factors they are not considering?

Studies have shown that high-BMI women have longer menstrual cycles and longer gestations; perhaps what is happening is that their due dates are not being sufficiently adjusted for their longer cycle length and as a result, their bodies are less ready for labor when the doctors think they "should" be going into labor. And, as a result, they have more inductions, less cervical ripeness when induced, and more cesareans when the induction doesn't work.

More Interventions

The study found that there was more use of oxytocin augmentation and epidurals as BMI increased.  The pit augmentation increase may reflect the lower level of cervical ripeness before labor, but it may also reflect the common perception among some clinicians that obese women won't labor sufficiently on their own. So they automatically just start pitocin augmentation, without ever looking at whether it's needed or not.

The increased epidural rate may simply reflect the higher rate of inductions and pitocin augmentations; it's hard to go through such induced and augmented labors with little mobility and not need some pain relief.  However, it may also reflect the common practice of strongly encouraging early epidural placement in obese women to avoid a difficult placement later if a cesarean is needed.

(And of course, once that epidural is placed, oxytocin augmentation is often needed to compensate for the way that epidurals tend to slow labor.  It can be an vicious circle.)

Lower Surgical Threshold

The study also shows that doctors were quicker to terminate labor early and move to a cesarean in "obese" women.  In the study, the labors of "morbidly obese" women were terminated about an hour earlier than women of average BMI.

Some of this is understandable; surgery in a very heavy woman is more difficult and takes quite a bit longer than in a woman of average size.  Doctors want to avoid an emergency situation where every second counts to save a baby, and especially so in a woman whose extensive adipose layers may require more time to get to the baby in the first place.  Therefore, doctors may be more prone to intervene early in women of size, before things get to an emergency situation.

Yet most cesareans are not done under truly emergent conditions, and research shows that many women whose progress is slow are able to give birth vaginally if just given a little more time, and their babies generally do just as well.

So doctors have to walk a fine line between not waiting too late and not intervening too early.  From this study, it looks like too many doctors are erring on the side of intervening far too early.  And because cesareans are extra risky for women of size, this is a cause for concern ─ and a potentially modifiable variable for reducing the tremendously high cesarean rate in women of size.

Final Thoughts

As I've been saying for years, the high cesarean rate in obese women is not only about obesity itself, but also about the way that obese women are managed during pregnancy.

Sky-high induction rates, increased utilization of interventions during labor, and a very low threshold for surgical intervention all combine to ratchet up the cesarean rate in women of size.

The important thing to note is that these are all potentially modifiable factors for reducing the cesarean rate in this group.  

Up till now, the only options most doctors saw for lowering the cesarean rate in women of size involved  encouraging weight loss before pregnancy or restricting weight gain during pregnancy.  Yet this research suggests that if doctors simply change their management practices and fear levels around women of size, it's likely that the cesarean rate can be lowered in this group without draconian weight restrictions.

In the Canadian study, the authors concluded: 

Because of the potential morbidities associated with Caesarean section, we must modify our management approaches to allow equal opportunity for a vaginal birth for all women.

Those are strong words for an obstetrical community that's usually pretty mealy-mouthed about these things, and frankly, it's nice to finally hear them from someone other than me.  Bravo to these authors for being willing to advocate for vaginal birth for women of size at a time when some doctors are advocating pre-emptive cesareans across the board for this group.

But if doctors really want to get serious about allowing equal opportunity for a vaginal birth for fat women, first and foremost they need to crack down on the insanely high induction rates, as well as re-examining the use of interventions and threshold for surgery in this group.


References

J Obstet Gynaecol Can. 2011 May;33(5):443-8. Higher caesarean section rates in women with higher body mass index: are we managing labour differently? Abenhaim HA, Benjamin A.  PMID: 21639963

Background: Higher body mass index has been associated with an increased risk of Caesarean section. The effect of differences in labour management on this association has not yet been evaluated.

Methods: We conducted a cohort study using data from the McGill Obstetrics and Neonatal Database for deliveries taking place during a 10-year period. Women's BMI at delivery was categorized as normal (20 to 24.9), overweight (25 to 29.9), obese (30 to 39.9), or morbidly obese (≥ 40). We evaluated the effect of the management of labour on the need for Caesarean section using unconditional logistic regression models.

Results: Data were available for 11 922 women, of whom 2289 women had normal weight, 5663 were overweight, 3730 were obese, and 240 were morbidly obese. After adjustment for known confounding variables, increased BMI category was associated with an overall increase in the use of oxytocin and in the use of epidural analgesia, and with a decrease in use of forceps and vacuum extraction among second stage deliveries. 

Higher BMI was also found to be associated with earlier decisions to perform a Caesarean section in the second stage of labour. 

When adjusted for these differences in the management of labour, the increasing rate of Caesarean section observed with increasing BMI category was markedly attenuated (P less than 0.001). 

Conclusion: Women with an increased BMI are managed differently in labour than women of normal weight. This difference in management in part explains the increased rate of Caesarean section observed with higher BMI.

Aust N Z J Obstet Gynaecol. 2011 Apr;51(2):172-4. Impact of morbid obesity on the mode of delivery and obstetric outcome in nulliparous singleton pregnancy and the implications for rural maternity services. Green C, Shaker D.  PMID: 21466521

Obesity represents a rapidly emerging epidemic amongst pregnant women. Our study looks at the impact of morbid obesity on pregnant singleton nulliparous women in comparison with normal body mass index women. We conclude that morbid obesity is associated with a significantly higher risk of pre-existing medical conditions, developing antenatal complications, induction of labour, caesarean section and greater birth weight. However, there was no significant difference in caesarean section rates when adjusted for induction of labour. We also found no significant difference in length of hospital stay, postnatal complications and neonatal morbidity.