Labor Length in "Obese" Women: Dig Deeper

Here's the abstract of an interesting study suggesting that the first stage of labor (dilation) is longer in "obese" women and that this ought to be taken into account when diagnosing labor arrest needing a cesarean in this group.

This is not the first study to find a longer length of labor in higher-BMI women. As a result of these differences, one study concluded:

It is critical to consider differences in labor progression by maternal prepregnancy BMI before additional interventions are performed.

I agree that a possible longer labor length ought to be taken into account before resorting to a cesarean. As we've discussed before, many cesareans are done for "Failure to Wait" rather than for a true emergency, and many cesareans in women of all sizes could probably be avoided if care providers were a little more patient during labor.

In fact, a recent joint statement from the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine suggested that women be allowed a longer time in early ("latent") labor, that women not be considered to be in "active labor" until 6 cm (instead of 4 cm), and that they be given more time both in active labor and in the pushing stage before the doctor starts thinking cesarean.

This may be especially meaningful for high BMI women, as there tends to be a lower surgical threshold for women of size. In one study, labor in obese women was terminated by cesarean an hour earlier on average than in other women. This shows that some doctors are nervous in the labors of obese women and jump to a surgical solution far too quickly.

On the one hand, it is understandable that doctors are nervous about doing a truly emergent cesarean in obese women, since accessing the baby takes longer and the surgery is more difficult. On the other hand, if doctors jump to cesareans too quickly, many obese women who might have given birth vaginally are exposed to the substantial risks of surgery. And since many women of size these days are strongly discouraged from VBAC, this often means further cesareans, which is even more risky.

It's important to acknowledge that it can be difficult for providers to judge whether or not labor should continue in obese women with slow labors. However, provided the fetus is doing well, this study suggests that care providers should be more patient in the labors of women of size. 

Yes! That's something I've been saying for a while now.

Digging Deeper

However, I'd also like researchers to dig even further into why our labors may be longer.

There is some research to suggest that women of size have higher rates of posterior (OP) babies, and OP babies often have prolonged labors. I wish this study's database had fetal position recorded so they could have checked out this possibility.

Do obese women really have more posterior babies? Is that why they tend to have longer labors and more cesareans for dystocia? Or is it a relative lack of responsiveness to oxytocin, as some authors have suggested?

A number of older studies on obesity and pregnancy noted higher rates of fetal malpositions, particularly OP. Most newer studies have not looked for a connection, although the study linked above does note higher OP rates in obese women. Anecdotally, my own birth stories and the birth stories of many fat women I've received over the years for my website seems to support the idea of a higher rate of malpositions as well. All this suggests a connection, but of course we need data to back that up.

I would love to see someone, somewhere research the fascinating question of whether women of size have more malpositioned babies and whether this is one factor behind slower labor rates in this group. I'm sure it's not the only factor, but I would guess that it is a significantly underestimated factor.

If you are a woman of size reading this post, don't panic and think you're doomed to have a really long labor just because you are heavier. On average, our labors tend to be longer, but there's no way to predict labor length for any one person.

SO MUCH of labor length has to do with the position of the baby, whether or not labor is induced, how ripe the woman's cervix is, whether the woman can be mobile in labor, and many other factors. I've known fat women who have had 2 hour labors, and I've known fat women who have had very long labors. My own four labors varied from 8 hours to nearly 20 hours ─ same-sized woman every time but the difference was well-positioned babies vs. OP babies. So labor length really can be highly variable, even within the same person's experiences.

Summary

A combination of a tendency towards longer labor and a lower surgical threshold for cesarean, along with more inductions, is probably why the cesarean rate in high BMI women has risen so high. Because obese women have more complications with cesareans, it is important to discover how to lower this rate.

The take-away message from this study is that, on average, the labors in high BMI women were longer, and their care providers probably should take that into account and wait a little longer before diagnosing a labor arrest disorder and doing a cesarean.

If you are a woman of size, find a care provider who truly believes that you can have a vaginal birth and who is willing to be more patient in labor before resorting to a cesarean. (Generally speaking, midwives tend to be more willing to wait, although some OBs are great about this too. Don't depend on a title but ask careful questions to better understand a provider's practice style.)

If you are a researcher, dig a little deeper and explore why women of size have longer labors, including whether or not there is a higher rate of fetal malpositions. I suspect there is but I'd love to see recent data to confirm this.

If there are more OP babies in heavier women, then there are things that women of size can do that might help lower their chances of a malpositioned baby before labor (chiropractic care is what helped me). Additionally, there are things a care provider can do during labor to help turn a malpositioned baby if needed (research on manual rotation is very promising). And of course, sometimes all that's needed for an OP baby is to have a little more patience in labor.

Whether it's being more patient in labor, doing fewer inductions, or being more proactive about fetal position in women of size, there are things we can do to lower the cesarean rate in this group. It's about time we start doing them. 


Reference

Eur J Obstet Gynecol Reprod Biol. 2013 Nov;171(1):49-53. doi: 10.1016/j.ejogrb.2013.08.021. Epub 2013 Aug 29. Maternal body mass index and duration of labor. Carlhäll S1, Källén K, Blomberg M. PMID: 24041847

OBJECTIVE: To evaluate whether the duration of the active phase of labor is associated with maternal body mass index (BMI), in nulliparous women with spontaneous onset of labor. STUDY DESIGN: Historical prospective cohort study including 63,829 nulliparous women with a singleton pregnancy and a spontaneous onset of labor, who delivered between January 1, 1995 and December 31, 2009. Data were collected from the Perinatal Revision South registry, a regional perinatal database in Southern Sweden. Women were categorized into six classes of BMI. Overweight and obese women were compared to normal weight women regarding duration of active labor. Adjustments were made for year of delivery, maternal age and infant birth weight. RESULTS: The median duration of labor was significantly longer in obese women (class I obesity (BMI 30-34.9) = 9.1h, class II obesity (BMI 35-39.9) = 9.2h and class III obesity (BMI > 40) = 9.8h) compared to normal-weight women (BMI 18.5-24.9) = 8.8h (p < 0.001). The risk of labor lasting more than 12h increased with increasing maternal BMI: OR 1.04 (1.01-1.06) (OR per 5-units BMI-increase).The risk of labor lasting more than 12h or emergency cesarean section within 12h, compared to vaginal deliveries within 12h, increased with increasing maternal BMI. Duration of the second stage of labor was significantly shorter in obese women: in class III obesity the median value was 0.45 h compared to normal weight women, 0.55 h (p < 0.001). CONCLUSION: In nulliparous women with a spontaneous onset of labor, duration of the active phase of labor increased significantly with increasing maternal BMI. Once obese women reach the second stage they deliver more quickly than normal weight women, which implies that the risk of prolonged labor is restricted to the first stage of labor. It is clinically important to consider the prolonged first stage of labor in obese women, for example when diagnosing first stage labor arrest, in order to optimize management of this rapidly growing at-risk group of women. Thus, it might be reasonable to adapt the considered upper limit for duration of labor, according to maternal BMI.

Increase in Cesarean Rate in Morbidly Obese Women Over Time

Here's the abstract of an interesting new study. I haven't seen the full text yet but it appears to show that while the cesarean rate has gone up over time in all sizes of women, it's gone up the most in the higher BMI categories.

In other words, a high BMI woman is far more likely to have a cesarean now than she was in 1990.

This shows that the high cesarean rate in obese women is not just about obesity itself, but also how obese women are managed in labor and the lowering of the surgical threshold for performing cesareans in high BMI women.

I've been saying this for years. Some care providers like to pretend that the high cesarean rate in obese women is only about the woman's fatness, as if this somehow prevents a fat woman from giving birth vaginally (the classic "fat vagina" theory).

But if it was really only about physical barriers, then you would see a relatively consistent cesarean rate in this group over time, and you DON'T. This study shows that there used to be much lower cesarean rates in women of size than there is today, and older studies show that the cesarean rate wasn't always higher in obese women than in average-sized women.

Critics would point out that the cesarean rate has increased in all groups over time, not just in obese women. Sad, but true.

But the cesarean rate has not increased equally in every group, as this study points out. Look at their comparison of cesarean rates between 1990 and 2012 by BMI group*:

                              1990                     2012                   Increase

Underweight         14.4%                   27.9%                  13.5%
Normal                  16.1%                   31.4%                  15.3%
Overweight           19.5%                   38.8%                  19.3%
Obese I                 22.3%                   45.1%                  22.8%
Obese II                25.0%                   50.2%                  25.2%
Obese III               26.9%                   55.2%                  28.3%

The increase in cesarean rates was not uniform across BMI categories. The increase in "normal" weight women was 15.3%, but the increase in Obese Class III women was nearly twice that at 28.3%.

In 1990, Obese class III women had a 26.9% cesarean rate in 1990....just over 1 in 4.

In 2012, Obese Class III women  had a 55.2% cesarean rate instead, or more than 1 in every 2 "morbidly obese" women.

In just 22 years, the cesarean rate in Class III Obese women went from 26.0% to 55.2%. How far will it go in the next 20 years?

Something has changed...and that something is probably how those women are managed in labor (more interventions), the exaggeration of fear around their pregnancies, and the resulting lowering of the surgical threshold for a cesarean in that group.

Similarly, research shows that cesarean rates in the same BMI group can vary dramatically between locations. For example, recent studies from Tennessee and Kentucky show an abysmal cesarean rate of nearly 60% in "morbidly obese" women. One particularly appalling study from Michigan shows a cesarean rate of over 80% in women with a BMI over 50.

Yet a large study from the U.K. shows a cesarean rate of about 30% in the same population.

This shows that practice variation is an issue not only in the overall population, but perhaps particularly in high BMI women.

It's time for care providers to examine not only how to prevent questionable cesareans in women across the board, but also to focus on how to prevent questionable cesareans in high-BMI women. Given that cesareans carry more risks in women of size, especially multiple repeat cesareans, it's inexcusable to be exposing so many of these women to these risks unnecessarily.

The cesarean rate is high is women of size, but the variation in rates over time and between locations shows it doesn't have to be, and that there are things we could be doing to bring the cesarean rate down in this group.

It's long past time to be looking into that question. Some researchers are starting to ask these questions or propose solutions, but few have actually tested these theories.

Where are the researchers and providers willing to actually study how to lower the cesarean rate in women of size?


References

J Perinat Med. 2014 Jun 10. pii: /j/jpme.ahead-of-print/jpm-2014-0126/jpm-2014-0126.xml. doi: 10.1515/jpm-2014-0126. [Epub ahead of print] Impact of maternal body mass index on the cesarean delivery rate in Germany from 1990 to 2012. Kyvernitakis I, Köhler C, Schmidt S, Misselwitz B, Großmann J, Hadji P, Kalder M. PMID: 24914711

ABSTRACT AIMS: Maternal obesity is a risk factor for cesarean delivery (CD). The aim of this analysis was to determine the association between early-pregnancy body mass index (BMI) and the rate of CD over the past two decades. METHODS: We retrospectively analyzed data from the perinatal quality registry of singleton deliveries in the state of Hesse in Germany from 1990 to 2012. We divided the patients into groups according to the WHO criteria for BMI: underweight (<18.5), normal weight (18.5-<25), overweight (25-<30), obese class I (30-<35), obese class II (35-<40), and obese class III (≥40). RESULTS: The analysis included 1,092,311 patients with available data regarding maternal BMI and mode of delivery. The CD rates for underweight (<18.5), normal weight (18.5-<25), overweight (25-<30), obese class I (30-<35), obese class II (35-<40), and obese class III (≥40) women increased from 14.4%, 16.1%, 19.5%, 22.3%, 25%, and 26.9% in the year 1990 to 27.9%, 31.4%, 38.8%, 45.1%, 50.2%, and 55.2% in the year 2012, respectively (P<0.001). CONCLUSION: Maternal BMI in early pregnancy is linearly associated with the incidence of CD. We found a disproportionate increase of CD in morbidly obese women compared with the CD incidence in the reference BMI population over the past two decades.

* Standard BMI classifications: 

• "Underweight" = BMI less than 18
• "Normal" weight = BMI 18-24.9
• "Overweight" = BMI 25-29.9
• Class I Obese = BMI 30-34.9
• Class II Obese = BMI 35-39.9
• Class III Obese = BMI of 40 plus
• "Super Obese" = BMI of 50 plus

See my Practice Variation Post at Science and Sensibility

My recent post on Practice Variation in Cesarean Rates went a bit viral. (Thank you to those of you who shared it on Facebook!)

The blog, Science and Sensibility (Lamaze International’s “Research Blog About Healthy Pregnancy, Birth & Beyond”), picked it up and asked to run it since it's very topical right now, what with the recent important study on Practice Variation.

I revised my very-quick original post and expanded on a few points, added some new research, reformatted it a bit, and generally prettified it up. (I spent all my time on that, so no new post here till next week.)

In the meantime, the revised post is now up on Science and Sensibility. You can go and read it here.

Practice Variation in Cesarean Rates: Not Due to Maternal Complications

Photo courtesy "Angela"

There's a new study out that discusses the variation in cesarean rates between hospitals in the United States.

Practice variation is a serious problem in obstetrics. Women are often far more at risk for a cesarean in certain hospitals than in others, even when the hospitals serve the same geographical area and population.

Of course, care providers protest that some hospitals have higher cesarean rates because they serve higher-risk patients. This is a valid point, but it still doesn't explain the wide variation in rates between many hospitals.

For example, in the study above, the mother's risk status and diagnoses did not explain the variation in cesarean rates between hospitals:

“We found that the variability in hospital cesarean rates was not driven by differences in maternal diagnoses or pregnancy complexity,” said [lead study author] Kozhimannil. “This means there was significantly higher variation in hospital rates than would be expected based on women’s health conditions. On average, the likelihood of cesarean delivery for an individual woman varied between 19 and 48 percent across hospitals.”

There were several key points highlighted in the article about the study, including:

• Among lower risk women, likelihood of cesarean delivery varied between 8 and 32 percent across hospitals.
• Among higher risk women, likelihood of cesarean delivery varied between 56 and 92 percent across hospitals.
• Hospital variability did not decrease after adjusting for patient diagnoses, socio-demographics, and hospital characteristics.

This shows that practice variation in cesarean rates is real, substantive, and not just a reflection of the mother's risk level. 

Perhaps now we can stop playing the mother blame-game when we talk about cesarean rates?

This study is not the first to show that the culture of a hospital, their policies, and their routine practices all help determine how likely a woman is to "need" a cesarean in that hospital.

This is important because while cesareans can be life-saving at times, they present more risk for infection, bleeding, pain, neonatal breathing problems, and complications in future pregnancies. It matters where and with whom a woman gives birth.

But many women naively choose their care provider for pregnancy based mostly on convenience and location, not realizing that their chances of surgical birth may vary greatly depending on which hospital and caregiver they use. 

One leading consumer education site points out, "Research suggests that the same woman might have a c-section at one hospital but a vaginal birth if she gave birth at another, just because of the different policies and practices of those hospitals. One of the most effective ways to lower your chance of having a c-section is to have your baby in a setting with a low c-section rate."

Yet it is not always easy to find out the cesarean rates* of local hospitals in some states, and many hospitals remain largely unaccountable for sky-high cesarean rates, although we are beginning to see marginal progress in some places towards accountability. But even when a cesarean is truly necessary, there can be large discrepancies in complications afterwards between hospitals. How is a woman to know which hospital to choose?

Bottom line, more transparency and accountability are needed. As the lead author of the study states: 

Women deserve evidence-based, consistent, high-quality maternity care, regardless of the hospital where they give birth...and these results indicate that we have a long way to go toward reaching this goal in the U.S.

**An additional suggestion: Researchers should start examining cesarean practice variations in obese patients too. Research strongly suggests there are major practice variations in cesarean utilization for "obese" mothers between hospitals, yet this is a topic that is rarely broached in research. More exploration of this dichotomy might help reduce the cesarean rate in this group.

***Post received minor reference and picture edits on 11/6/14.

References

*See www.cesareanrates.com for hospital level cesarean rates in most U.S. states. Consumer Reports also has a recent article with some hospital-level c-section rates in the U.S.

PLoS Med. 2014 Oct 21;11(10):e1001745. doi: 10.1371/journal.pmed.1001745. eCollection 2014. Maternal Clinical Diagnoses and Hospital Variation in the Risk of Cesarean Delivery: Analyses of a National US Hospital Discharge Database. Kozhimannil KB1, Arcaya MC2, Subramanian SV2. PMID: 25333943

BACKGROUND: Cesarean delivery is the most common inpatient surgery in the United States, where 1.3 million cesarean sections occur annually, and rates vary widely by hospital. Identifying sources of variation in cesarean use is crucial to improving the consistency and quality of obstetric care. We used hospital discharge records to examine the extent to which variability in the likelihood of cesarean section across US hospitals was attributable to individual women's clinical diagnoses. METHODS AND FINDINGS: Using data from the 2009 and 2010 Nationwide Inpatient Sample from the Healthcare Cost and Utilization Project-a 20% sample of US hospitals-we analyzed data for 1,475,457 births in 1,373 hospitals. We fitted multilevel logistic regression models (patients nested in hospitals). The outcome was cesarean (versus vaginal) delivery. Covariates included diagnosis of diabetes in pregnancy, hypertension in pregnancy, hemorrhage during pregnancy or placental complications, fetal distress, and fetal disproportion or obstructed labor; maternal age, race/ethnicity, and insurance status; and hospital size and location/teaching status. The cesarean section prevalence was 22.0% (95% confidence interval 22.0% to 22.1%) among women with no prior cesareans. In unadjusted models, the between-hospital variation in the individual risk of primary cesarean section was 0.14 (95% credible interval 0.12 to 0.15). The difference in the probability of having a cesarean delivery between hospitals was 25 percentage points. Hospital variability did not decrease after adjusting for patient diagnoses, socio-demographics, and hospital characteristics (0.16 [95% credible interval 0.14 to 0.18]). A limitation is that these data, while nationally representative, did not contain information on parity or gestational age. CONCLUSIONS: Variability across hospitals in the individual risk of cesarean section is not decreased by accounting for differences in maternal diagnoses. These findings highlight the need for more comprehensive or linked data including parity and gestational age as well as examination of other factors-such as hospital policies, practices, and culture-in determining cesarean section use.

Am J Obstet Gynecol. 2007 Jun;196(6):526.e1-5. Variation in the rates of operative delivery in the United States. Clark SL1, Belfort MA, Hankins GD, Meyers JA, Houser FM. PMID: 17547880

OBJECTIVES: This study was undertaken to examine the national and regional rates of operative delivery among almost one quarter million births in a single year in the nation's largest healthcare delivery system, using variation as an arbiter of the quality of decision making. STUDY DESIGN: We compared the variation in rates of primary cesarean and operative vaginal delivery in facilities of the Hospital Corporation of America during the year 2004. RESULTS: In 124 facilities representing almost 220,000 births during a 1-year period, the primary cesarean and operative vaginal delivery rates were 19% +/- 5% (range 9-37) and 7% +/- 4% (range 1-23). Within individual geographic regions, we consistently found variations of 200-300% in rates of primary cesarean delivery and variations approximating an order of magnitude for operative vaginal delivery. CONCLUSION: Within broad upper and lower limits, rates of operative delivery in the United States are highly variable and suggest a pattern of almost random decision making. This reflects a lack of sufficient reliable, outcomes-based data to guide clinical decision making.

Neonatology. 2014 Oct 4;107(1):8-13. [Epub ahead of print] Women Are Designed to Deliver Vaginally and Not by Cesarean Section: An Obstetrician's View. Visser GH. PMID: 25301178

Worldwide, there is a rapid increase in deliveries by cesarean section. The large differences among countries, from about 16% to more than 60%, suggest that the cesarean delivery (CD) rate has little to do with evidence-based medicine. In this review, the background for the increasing CD rate is discussed as well as the limited positive effects on neonatal outcome in both term and preterm neonates. Negative effects of CD, including direct maternal morbidity, complications of subsequent pregnancies and iatrogenic early delivery resulting in increased neonatal morbidity, are discussed in addition to long-term implications for the offspring involving altered development of the immune system. The 'battle' to lower the CD rate will be difficult, but we should not forget that women are designed to deliver vaginally and not by cesarean section.