Low Prenatal Weight Gain Does Not Prevent Blood Pressure Issues in "Obese" Women

One idea often promoted by care providers is that keeping prenatal weight gains to the minimum possible or losing weight in pregnancy will prevent blood pressure issues (Gestational Hypertension or Pre-Eclampsia) in "obese" women.

One of the most dreaded complications of pregnancy is blood pressure issues like GHTN and PE, and obese women really are at increased risk for these complications. It is understandable that care providers want to try to prevent that if at all possible.

However, here is a recent study that shows that losing weight and very low gains in pregnancy did not lower the rate of Gestational Hypertention (GHTN) or Pre-Eclampsia (PE) in obese women.

This is important because, as we have discussed before, more and more providers are zeroing in on weight gain in pregnancy as a way to try and prevent complications in higher weight women.

There have been studies which found that lower weight gains were correlated with lower rates of pre-eclampsia, and higher gains with higher rates of pre-eclampsia. However, this doesn't mean that deliberately restricting weight gain prevents PE. As Nohr 2008 states:

Any causal interpretation of the association between total weight gain and these complications is limited. For preeclampsia, high total gain most likely reflects pathologic fluid retention as part of the disease.

In other words, just because very low gain is associated with less pre-eclampsia, it does not follow that making women gain very little weight during pregnancy will prevent pre-eclampsia. Instead, higher weight gain is usually simply a side effect of pre-eclampsia due to the fluid retention and swelling common to pre-eclampsia.

Despite this, many caregivers imply that women can prevent pre-eclampsia by controlling their weight gain during pregnancy. Some are resorting to "scorched earth" tactics, including some truly frightening and extreme nutritional advice, or by encouraging women to lose weight during pregnancy.

This latest study shows that blood pressure issues in pregnancy can't be reliably prevented by having obese women gain minimally or even by losing weight while pregnant. 

Care providers should not be putting higher-weight women on extreme restrictions while pregnant, nor should they be expecting them to lose weight.

Too many care providers see weight gain within recommended limits as a surrogate marker of a woman's nutrition and exercise habits. Women can gain "appropriately" and still have terrible nutrition, and women can gain above or below the recommended limits and still have great nutrition and habits. Discussions about weight gain in pregnancy need to move beyond the scale.

While it's perfectly appropriate to inform higher-weight women of the most optimal prenatal weight gain range to shoot for and to give them reasonable counseling about how to do so, it's much more important to emphasize great nutrition and regular exercise. Then trust the woman's body to gain what it needs to gain for that pregnancy.


Reference

Am J Perinatol. 2014 Dec 8. [Epub ahead of print] The Influence of Gestational Weight Gain on the Development of Gestational Hypertension in Obese Women. Barton JR, Joy SD, Rhea DJ, Sibai AJ, Sibai BM. PMID: 25486285

OBJECTIVE: The objective of this study was to examine the influence of gestational weight gain on the development of gestational hypertension/preeclampsia (GHTN/PE) in women with an obese prepregnancy body mass index (BMI). 

METHODS: Obese women with a singleton pregnancy enrolled at < 20 weeks were studied. Data were classified according to reported gestational weight gain (losing weight, under-gaining, within target, and over-gaining) from the recommended range of 11 to 9.7 kg and by obesity class (class 1 = BMI 30-34.9 kg/m2, class 2 = 35-39.9 kg/m2, class 3 = 40-49.9 kg/m2, and class 4 ≥ 50 kg/m2). Rates of GHTN/PE were compared by weight gain group overall and within obesity class using Pearson chi-square statistics. 

RESULTS: For the 27,898 obese women studied, rates of GHTN/PE increased with increasing class of obesity (15.2% for class 1 and 32.0% for class 4). The incidence of GHTN/PE in obese women was not modified with weight loss or weight gain below recommended levels. Overall for obese women, over-gaining weight was associated with higher rates of GHTN/PE compared with those with a target rate for obesity classes 1 to 3 (each p < 0.001). 

CONCLUSION: Below recommended gestational weight gain did not reduce the risk for GHTN/PE in women with an obese prepregnancy BMI. These data support a gestational weight gain goal ≤ 9.7 kg in obese gravidas.

Common Sense Prenatal Weight Gain Recommendations for "Obese" Women

The 2009 IOM Guidelines for Prenatal Weight Gain

Coming up with official prenatal weight gain guidelines is difficult. There's always a trade-off involved ─ too much weight gain increases the risk for large babies, but too little increases the risk for small babies.

(The effects of weight gain on cesarean rates and pre-eclampsia are harder to figure out because of multiple variables that influence outcomes, so we will limit our discussion for a moment to the influence of weight gain on fetal outcomes.)

This weight gain trade-off has been particularly difficult to figure out in women of size. We tend to have larger babies on average and a very big weight gain seems to increase fetal size particularly strongly in high-BMI women. Nor do we need to gain extra fat reserves for pregnancy and breastfeeding. As a result, the Institute of Medicine (IOM) recommends less weight gain on average for "obese" women (see chart above).

While I don't hate these recommendations, I do have some concerns with them, particularly for women in the borderline categories (see discussion below). Women in these categories may be particularly at risk for poor outcomes, yet they are given the same stringent guidelines (and are often told to gain even less than the guidelines).

I also question how much control women really have over gestational weight gains. Sure, we have control over how much we eat and exercise, but that impact on gain is fairly minimal. There have been many trials of interventions to help obese women keep their weight gains lower; some have had minimal success (about 5 lbs. difference), but many have made little difference in weight gain and do little to improve other outcomes. Even with the best support, many women of size gain above the guidelines ─ not because they are lazy or out of control, but because the guidelines aren't particularly realistic for them.

I am also concerned about harassment and over-intervention in the pregnancies of women who gain above these recommended ranges. I have heard many stories of women of size who are harassed or even punished with early inductions or planned cesareans because they "gained too much."

So while I agree in general with the IOM that obese women don't need to gain as much weight in pregnancy as other women, I do have some reservations about the IOM guidelines and in particular about how they are implemented. But sadly, even these guidelines are not stringent enough for some providers.

Taking The 2009 Guidelines Even Further

Some caregivers believe the 2009 IOM weight gain goals didn't go far enough for obese women. In recent years, unofficial prenatal weight gain advice has gotten progressively more extreme. I call this the "anorexation" of pregnancy weight gain guidelines.

The following are real-life headlines from media articles over the years. Notice how the headlines have changed. They have gone from "obese women should gain LESS weight".....

...to "obese women should gain NO weight"

....to "obese women should LOSE weight" during pregnancy.

Disturbingly, many experts have taken an extremist tone in the media and sold these draconian measures as a public health imperative, which alarms me greatly. Many news articles have pushed this weight restriction agenda, assuring us that very little gain was perfectly safe and even healthier for the plus-sized mother and her baby. Here are just a couple of examples.

One article about the IOM recommendations prominently featured the following quotes promoting even lower gains in high-BMI women:

"I think 11 to 20 pounds is way too much for an obese woman," said Dr. Thomas Myles, a professor of obstetrics and gynecology at Saint Louis University School of Medicine who was not involved in the current recommendations. "I usually tell my [obese] patients that gaining less than 10 pounds and even losing up to 10 pounds is appropriate, whereas for overweight women, gaining 10 to 15 and even up to 20 pounds is appropriate," Myles said. 

Gaining a little less weight than the recommended amount, especially for overweight and obese women, might be better, [Associate Professor, Dr. Emily] Oken [of Harvard University] said.

Another article promoting zero weight gain in obese women featured the following quote from one of its leading investigators in its study's press release (my emphasis):

It may seem counterintuitive to suggest that women control their weight during pregnancy, but these women are already carrying between 50 and 100 extra pounds — and for them any more weight gain could be very dangerous,” said Vic Stevens, PhD, principal investigator who has studied weight loss and weight maintenance for more than 30 years.

Another recent article quoted Dr. Sigal Klipstein, Chair of the American College of Obstetricians and Gynecologists committee on Medical ethics. Even as she discussed the importance of treating obese women humanely during pregnancy, Dr. Klipstein stated:

Although women should not to try to lose weight during pregnancy, “a woman who weighs 300 pounds shouldn’t gain at all,” Klipstein said. “This is not harmful to the fetus.”

But is it really true that very small or non-existent gains are not harmful?

Risks of Too-Small Gains

Those who suggest that gaining little or no weight is optimal for women of size are ignoring all the contrary research.

A significant amount of research has shown that very low weight gains and/or weight loss during pregnancy in women of size carries real risks, including

• prematurity (Dietz 2006, Potti 2010, Hasegawa 2012)
• too-small babies (Vesco 2011, Catalano 2014)
• more need for intensive care in the NICU (Potti 2010)

Tellingly, virtually NO media articles acknowledge that low weight gains have risks or cite the research that shows this. That there are so many articles promoting restricted gain in obese women while completely ignoring the potential harms of such a policy suggests a health agenda that places ideology over evidence.

And now there is even more research suggesting that very low gains may be risky.

A very recent study (Durst 2016) showed that weight gains below the IOM recommendations in obese women led to increased rates of  small-for-gestational-age ("SGA") babies and pre-term births. Another recent study (Cox Bauer 2016) found that gestational weight loss (GWL) was associated with low-birth weight babies. These are a concern because too-small babies are more at risk for future health problems like metabolic syndrome and insulin resistance.

Still another recent study (Hannaford 2016) shows that too-low weight gains, even in obese women, more than doubled the risk for too-small babies. The authors suggested that there may need to be a threshold of a minimum weight gain, even for very high-BMI women, which is a pretty radical suggestion given how many doctors are calling for zero gain or weight loss in this group.

But these new studies are far from the first to find reasons for concern. A brand-new meta-analysis (Xu 2017) of studies on weight gain below the 2009 guidelines in obese mothers found that low weight gain was associated with SGA babies in all obesity categories, not just in the borderline categories.

Yet another meta-analysis (Kapadia 2015) of studies on weight gain in obese pregnant women concluded that, because of its consistent association with too-small babies,

Gestational weight gain below the guidelines cannot be routinely recommended.

Too-small babies and prematurity may not be the only risks of very low weight gains; they may also be implicated in infant deaths.

A recent study (Bodnar 2016) found that weight loss and very low weight gains in Class I and II obese women were associated with a higher risk of infant death.

This is particularly important because research is very clear that SGA babies have a higher risk for stillbirth and neonatal mortality. In addition, some past research (Salihu 2009) shows that SGA babies of obese women are at particular risk for stillbirth.

Sorry, but SGA babies, prematurity, and infant death are pretty significant concerns. People like Dr. Myles, Dr. Oken, Dr. Stevens, and Dr.Klipstein who have been recommending weight gains well below the IOM recommendations have been playing Russian Roulette with the babies of their patients of size.

This is a common problem in medicine ─ taking a recommendation to extreme lengths without adequately studying its safety first.

Obese women as a group may benefit from gaining less weight on average than other women, but it does NOT automatically follow that even less is better. 

Sadly, while now there are years of data suggesting harms with very low gains and/or gestational weight loss, many experts are STILL telling women of size and their providers that "any weight gain in overweight and obese patients is detrimental to pregnancy outcome." Any weight gain, really?

This bias towards ever-lowered weight gain goals is so ingrained that it continues to deny the existence of any contrary evidence. The 2013 article quoted above advises OB-GYNs:

Weight maintenance and even weight reduction have not proven harmful in obese pregnant patients according to studies in the recent literature

Not proven harmful? This statement completely ignores numerous studies published before 2013 pointing out safety concerns with this advice (Bayerlein 2011, Bodnar 2010, Blomberg 2011, Vesco 2011, Dietz 2006, Potti 2010, Hasegawa 2012).

And now we have EVEN MORE studies showing that there are safety concerns, yet this low/no gain/weight loss advice continues to be given routinely by many providers who assure their patients falsely that there is no reason to worry.

But What About....?

Critics will undoubtedly point out that some of these same studies show benefits of lower gains such as a modestly lower cesarean rate or lower rates of pre-eclampsia. These are valid points. However, that's a whole different discussion because multiple variables influence these complications and it's difficult to tease out a causal relationship.

For example, caregivers are not blinded to their patients' gains. A bigger gain may mean a bigger baby. Fear of a big baby can strongly influence the perception of when a cesarean is "needed" and how many interventions like induction are used. Research shows that women with larger weight gains are induced at higher rates. Therefore it may not be weight gain that's the issue, but rather how the caregiver responds to the gain.

Pre-eclampsia is another situation where you can't jump to conclusions about weight gain. Women with pre-eclampsia typically have a lot of swelling, which means a higher weight gain. As Nohr 2008 states:

Any causal interpretation of the association between total weight gain and these complications is limited. For preeclampsia, high total gain most likely reflects pathologic fluid retention as part of the disease.

In other words, a higher weight gain doesn't necessarily cause pre-eclampsia, but rather it often results from pre-eclampsia. It certainly doesn't mean that a lower weight gain will prevent pre-eclampsia. We just don't know if deliberately restricting weight gain will lower the rate of pre-eclampsia in obese women.

However, it must be acknowledged that too much weight gain is probably also not ideal. Prenatal weight gain clearly influences fetal size, and higher gains seem particularly particularly potent for larger fetal size in high-BMI women. Postpartum, a larger gain may also be difficult to lose; multiple pregnancies with large gains can result in a net overall weight increase that might possibly affect the mother's health. So doctors have to find a balance between the very real risk/benefit trade-offs of too much or too little gain in pregnancy.

That's not easy, and I acknowledge that. But it seems to me that the debate is still very unbalanced, with too many experts still not willing to acknowledge the very real risks of too-small gains.

Deliberately ignoring contrary research is not an evidence-based approach. It smacks of a weight restriction agenda instead of a reasoned approach to best practices.

Summary

For too long, "experts" have been waging a campaign to lower the 2009 IOM guidelines even further for obese women. As a result, many care providers have used draconian pressure on women of size to gain very little or even to lose weight in pregnancy. But there are significant safety concerns with this approach, concerns that these so-called experts are conveniently ignoring.

The research makes several things clear:

1. Very low weight gain or weight loss is extremely consistent with too-small babies in multiple studies 
2. Too-small babies are at increased risk for adulthood diseases
3. Weight loss and very low weight gains may also be associated with a higher risk for infant death and prematurity 

These concerns means it's time for caregivers to STOP promoting extreme weight gain limits and to START acknowledging that very low gains also carry risks. 

Now, it may be that in time, different weight gains will be recommended for different levels of obesity. That seems like a possibility that is worthy of further consideration.

For example, "overweight" women (BMI 25-29) and women with Class I obesity (BMI 30-35) seem to be the most negatively affected by very small weight gains, whereas some research shows that women with Class III obesity (BMI 40-50) and Class IV obesity (BMI 50+) are less affected on average by very low gains.

So there may be some gradations in recommendations in the future, and I welcome discussions about this possibility ─ but given the established risks and the meta-analysis of studies that showed increased SGA risks across all class sizes of obesity, it would still behoove us to be very cautious about recommending very low weight gain even in women with Class III and IV obesity. We simply cannot assume that restricting gains is harmless even there.

Common Sense Recommendations

To me, what's missing from prenatal weight gain recommendations for obese women is nuance. It's time to pull back from prenatal weight gain extremism and show some common sense. Here are the things I think caregivers should take into account when discussing pregnancy weight gain with women of size.

Women of size should be informed in a neutral way of the IOM weight gain recommendations and why they were made. A neutral discussion, with research citations as appropriate, goes a lot further to helping women make informed and empowered decisions. A decision about weight gain goals that comes from the woman herself, rather than being imposed by external forces, is a lot more likely to result in reasonable gains.

How the message is communicated is important. Women should be given reasonable nutritional advice and strongly encouraged to exercise, but risks should not be exaggerated. Lecturing, scare tactics, and condescension means that people will simply tune out recommendations. Treat women as competent partners in their own care and avoid judgment. Emphasize healthy habits rather than numbers on the scale.

Consider tailoring recommendations by BMI. Women in the borderline BMI classes are the most at risk for poor outcomes with very low gains; they should be encouraged to gain nearer to the top of the IOM recommendations. It may even be that women with Class I obesity (BMI 30-35) do best with slightly more gain (15-25 lbs.). Women in Class III (BMI over 40) and Class IV obesity (BMI over 50) can be encouraged to gain towards the lower end of the recommendations or even slightly lower (5-15 lbs.) but great care should be taken that this message does not translate into pressure for restricted intake or extreme measures. Do not assume that very high BMI women have adequate nutritional reserves to make up for a lack of gain; good nutrition is always the priority.

Do not promote actively losing weight in pregnancy. Research shows there are too many potential harms to recommend pursuing gestational weight loss. Some women of size lose without trying; this is not a cause for panic as long as intake is adequate and the baby is growing well. But actively encouraging women to aim for weight loss during pregnancy is different than coincidental weight loss, is likely to result in restrictive behaviors, and probably has far greater risk.

Consider patterns of gestational weight gain. Has the weight gain pattern been relatively smooth? Was there a very large gain in the beginning? At the end? Different patterns may indicate different concerns. Also, don't forget to take pre-conception weight into account; many obese women lose weight in the first trimester and slowly gain that back to a small overall gain. If the initial loss is not counted, it looks like the woman has gained more weight than she actually has. Look at the whole picture.

Do not harass women about weight gain. Weight-related harassment is obnoxious and inappropriate, but it is sadly all too common. Women should not feel afraid to step on the scale at appointments, yet they often experience harassment. Medical assistants should record weight without comment. Care providers can ask neutrally about gains and can work with women on monitoring nutrition and troubleshooting worrisome trends, but judgment and belittling will only backfire. If a woman gains outside of guidelines despite good nutrition and regular exercise, consider other possible variables. Assume that a woman's body will gain what it needs for a healthy pregnancy.

Avoid food extremism. Women of size should not be pressured to strongly restrict calories or to eliminate entire food groups. They should be encouraged to eat reasonable amounts from a wide variety of foods. Nutritional advice should be evidence-based, not from unproven diet trends. Caregivers need to find a way to talk to clients about nutrition and weight gain concerns without condescension or judgment. Work with women and listen to their feedback about their needs.

Individualize care according to the woman's needs. People of size are not all alike. Some fit stereotypical images of fast food consumption and binge eating, others have very healthy habits, and many fall somewhere in between. Ask them respectfully about their habits and concerns; don't make assumptions. Believe what they tell you and advise them accordingly. If habits need improvement, encourage small and reasonable steps and recognize positive achievements.

Remember that weight gains among high-BMI women are highly variable. Research shows that weight gains in pregnancy are less predictable in larger women. Some have very large gains, some have very small gains, and some lose weight without trying. Often the women who gain the most are those who have recently lost weight or who are chronic dieters/weight cyclers, those with lipedema, or those who have swelling with pre-eclampsia. Many factors influence gestational weight gain besides the habits of the women. Acknowledge that some weight gain may be out of their control.

Look more at how the mother and baby are doing than at the scale. Guidelines are more for groups than individuals. While research shows that very high or very low gains are generally best avoided on average, some obese women gain more or less than recommended and have perfectly healthy babies. Some gain a lot and have average-sized babies; some gain almost nothing and have big babies; some lose weight with no obvious harmful effect. Gaining outside the recommendations is not necessarily a cause for alarm, as long as the mother's intake is normal and baby is growing well.

Women should not be subjected to extra interventions if they exceed their providers' weight gain goals. Some fat women are being consciously punished for "too much weight gain" by being subjected to extra interventions like inductions or planned cesareans. However, some of these interventions may occur because of providers' underlying fears about big babies. Care providers must actively examine their own biases so that they do not unconsciously use increased interventions on those who gain more.

Most importantly, focus on nutrition rather than on the scale. Too many providers use weight gain as a marker of pregnancy status and ignore nutrition altogether. What a woman is eating matters more than how much weight she has gained. Women can be given a weight gain goal range, nutritional advice, and exercise opportunities, but nutrition should not be manipulated in order to achieve an arbitrary number. The scale is a poor predictor of outcome and should not be used as a surrogate for nutritional adequacy or fetal status. Focus more on nutrition and concrete signs of how the mother/baby dyad is doing than on numbers on a scale.

Care providers need to bring common sense back into prenatal weight gain guidelines and take a more nuanced approach with women of size.


References

Very Low Gain and Too-Small Infants (Latest Studies)

Am J Perinatol. 2016 Jun 29. [Epub ahead of print] Gestational Weight Gain: Association with Adverse Pregnancy Outcomes. Hannaford KE1, Tuuli MG, Odibo L, Macones GA, Odibo AO. PMID: 27355980 DOI: 10.1055/s-0036-1584583

...OBJECTIVES: We investigated how weight gain outside the IOM's recommendations affects the risks of adverse pregnancy outcomes. STUDY DESIGN: We performed a secondary analysis of a prospective cohort study including singleton, nonanomalous fetuses. The risks of small for gestational age (SGA), macrosomia, preeclampsia, cesarean delivery, gestational diabetes, or preterm birth were calculated for patients who gained weight below or above the IOM's recommendations based on body mass index category....Women who gained weight below recommendations were 2.5 times more likely to deliver SGA and twice as likely to deliver preterm...Obese patients who gained inadequate weight were 2.5 times more likely to deliver SGA. CONCLUSIONS: ...Among obese patients, a minimum weight gain requirement may prevent SGA infants.

Am J Perinatol. 2016 Jul;33(9):849-55. doi: 10.1055/s-0036-1579650. Epub 2016 Mar 9. Impact of Gestational Weight Gain on Perinatal Outcomes in Obese Women. Durst JK, Sutton AL, Cliver SP, Tita AT, Biggio JR. PMID: 2696070

...STUDY DESIGN: A retrospective cohort of perinatal outcomes in obese women who gained below, within, or above the 2009 Institute of Medicine guidelines and delivered ≥ 36 weeks. Additionally, outcomes, according to the rate of GWG (kg/week; minimal [< 0.16], moderate [0.16-0.49], or excessive [> 0.49]) were compared among women delivering preterm. RESULTS: Overall, 5,651 obese women delivered ≥ 36 weeks. GWG above guidelines was associated with increased cesarean section (adjusted odds ratio [aOR]: 1.44, 95% confidence interval [CI]: 1.21-1.72), gestational hypertension (aOR: 1.58, 95% CI: 1.21-2.06), and macrosomia (birth weight ≥ 4,000 g) (aOR: 2.08, 95% CI: 1.62-2.67). GWG below recommendations was associated with less large for gestational age infants (aOR: 0.60, 95% CI: 0.47-0.75)...Minimal weekly GWG was associated with increased spontaneous preterm birth (aOR: 1.56, 95% CI: 1.23-1.98) and more small for gestational age (SGA) infants (aOR: 1.55, 95% CI: 1.19-2.01). Excessive weekly GWG was associated with increased indicated preterm birth (aOR: 1.61, 95% CI: 1.29-2.01), cesarean section (aOR: 1.39, 95% CI: 1.20-1.61), preeclampsia (aOR: 1.83, 95% CI: 1.49-2.26), neonatal intensive care unit admission (aOR: 1.33, 95% CI: 1.08-1.63), and macrosomia (aOR: 2.40, 95% CI: 1.94-2.96).CONCLUSIONS: Obese women with excessive GWG had worse outcomes than women with GWG within recommendations. Limited GWG was associated with increased spontaneous preterm birth and SGA infants.

J Perinatol. 2016 Apr;36(4):278-83. doi: 10.1038/jp.2015.202. Epub 2016 Jan 7. Maternal and neonatal outcomes in obese women who lose weight during pregnancy. Cox Bauer CM, Bernhard KA, Greer DM, Merrill DC. PMID: 26741574

OBJECTIVE: To evaluate neonatal and maternal outcomes in obese pregnant women whose weight gain differed from the Institute of Medicine (IOM) recommendations. STUDY DESIGN: Maternal and neonatal outcomes associated with weight change in pregnancy were retrospectively investigated in women with obesity (body mass index (BMI) ⩾30 kg m(-2); N=10734) who gave birth at 12 hospitals...RESULT: Compared with IOM recommendations, weight loss was associated with twofold greater odds of low birth weight infants and a mean decrease in estimated blood loss of 30 ml; excessive weight gain was associated with doubled odds of gestational hypertension or preeclampsia, fourfold greater odds of macrosomia and a mean decrease in 5-min APGAR of 0.09....

J Matern Fetal Neonatal Med. 2017 Feb;30(3):357-367. Epub 2016 Apr 28. Inadequate weight gain in obese women and the risk of small for gestational age (SGA): a systematic review and meta-analysis. Xu Z, Wen Z, Zhou Y, Li D, Luo Z. PMID: 27033234

...We conducted a meta-analysis of original researches with sufficient information about inadequate GWG in obese women stratified by obesity classes. SGA as the chief outcome was extracted and assessed in our analysis...13 studies (437 512 obese women) were included. Obese women who gained weight below the guidelines had higher risks of SGA than those who gained weight within the guidelines (OR 1.28; 95% CI 1.14-1.43). The same conclusions were also confirmed in Class I, Class II and Class III of obese women: Class I (OR 1.37; 95% CI 1.22-1.54); Class II (OR 1.38; 95% CI 1.24-1.54); Class III (OR 1.25; 95% CI 1.14-1.36). CONCLUSIONS: From our analysis, the guidelines of IOM can be applied to all the classes of obesity. More accurate boundaries for each obesity class should be established to evaluate the maternal and fetal risks. Diverse populations are thus necessary for more studies in the future.

Low Weight Gain/SGA and Risk for Infant Death 

Obesity (Silver Spring). 2016 Feb;24(2):490-8. doi: 10.1002/oby.21335. Epub 2015 Nov 17. Maternal obesity and gestational weight gain are risk factors for infant death. Bodnar LM, Siminerio LL, Himes KP, Hutcheon JA, Lash TL, Parisi SM, Abrams B. PMID: 26572932

OBJECTIVE: Assessment of the joint and independent relationships of gestational weight gain and prepregnancy body mass index (BMI) on risk of infant mortality was performed. METHODS: This study used Pennsylvania linked birth-infant death records (2003-2011) from infants without anomalies born to mothers with prepregnancy BMI categorized as underweight (n = 58,973), normal weight (n = 610,118), overweight (n = 296,630), grade 1 obesity (n = 147,608), grade 2 obesity (n = 71,740), and grade 3 obesity (n = 47,277)...For all BMI groups except for grade 3 obesity, there were U-shaped associations between gestational weight gain and risk of infant death. Weight loss and very low weight gain among women with grades 1 and 2 obesity were associated with high risks of infant mortality....

Am J Perinatol. 2016 Aug 17. [Epub ahead of print] Morbidity and Mortality in Small-for-Gestational-Age Infants: A Secondary Analysis of Nine MFMU Network Studies. Mendez-Figueroa H1, Truong VT2, Pedroza C2, Chauhan SP1. PMID: 27533102

...Data from nine Maternal-Fetal Medicine Units Network studies were used and included nonanomalous singletons at 24 weeks or more and birth weight < 90% for EGA...Among SGA, the likelihood of stillbirth (8.8 vs. 2.5 per 1,000 births; adjusted odds ratio [aOR] 3.98, 95% confidence interval [CI]: 2.92-5.42) and neonatal mortality (14.0 vs. 5.5 per 1,000 births; aOR 3.18, 95% CI: 2.55-3.95) was threefold higher compared with AGA. For the subgroup of newborns of EGA of 32 weeks or more, SGA, compared with AGA, had significantly higher risk of stillbirth (aOR 3.32, 95% CI: 2.16-5.12) and neonatal mortality (aOR 2.50; 95% CI: 1.38-4.54). From 35 weeks onward, the risk of stillbirth among SGA is almost four times higher than for AGA. CONCLUSION: The risk of stillbirth and neonatal mortality is significantly higher with SGA than with AGA. Modification in practice or new management schema may be warranted.

Obstet Gynecol. 2009 Aug;114(2 Pt 1):333-9. Success of programming fetal growth phenotypes among obese women. Salihu HM, Mbah AK, Alio AP, Kornosky JL, Bruder K, Belogolovkin V. PMID: 19622995

...METHODS: This was a retrospective cohort study using the Missouri maternally linked cohort files (years 1978-1997)...Fetal growth phenotypes were defined as large for gestational age (LGA), appropriate for gestational age (AGA), and small for gestational age (SGA)...Neonatal mortality among LGA infants was similar for obese...and normal...weight mothers (OR 1.05, 95% confidence interval [CI] 0.75-1.48) and regardless of obesity subtype. By contrast, SGA and AGA infants programmed by obese mothers experienced greater neonatal mortality as compared with those born to normal weight mothers (AGA OR 1.45, 95% CI 1.32-1.59; SGA OR 1.72, 95% CI 1.49-1.98). CONCLUSION: Compared with normal weight mothers, obese women are least successful at programming SGA, less successful at programming AGA, and equally as successful at programming LGA infants.

Low Weight Gain and Risk for Prematurity

Obesity (Silver Spring). 2013 Dec;21(12):E770-4. doi: 10.1002/oby.20490. Epub 2013 Jul 5. Gestational weight loss and perinatal outcomes in overweight and obese women subsequent to diagnosis of gestational diabetes mellitus. Yee LM, Cheng YW, Inturrisi M, Caughey AB. PMID: 23613187

...Retrospective cohort study of 26,205 overweight and obese gestational diabetic women enrolled in the California Diabetes and Pregnancy Program. Women with GWL [Gestational Weight Loss] during program enrollment were compared to those with weight gain...RESULTS: About 5.2% of women experienced GWL. GWL was associated with decreased odds of macrosomia (aOR 0.63, 95% CI 0.52-0.77), NICU admission (aOR 0.51, 95% CI 0.27-0.95), and cesarean delivery (aOR 0.81, 95% CI 0.68-0.97). Odds of SGA status (aOR 1.69, 95% CI 1.32-2.17) and preterm delivery <34 weeks (aOR 1.71, 95% CI 1.23-2.37) were increased. CONCLUSIONS: In overweight and obese women with GDM, third trimester weight loss is associated with some improved maternal and neonatal outcomes, although this effect is lessened by increased odds of SGA status and preterm delivery. Further research on weight loss and interventions to improve adherence to weight guidelines in this population is recommended.

BJOG. 2011 Jan;118(1):55-61. doi: 10.1111/j.1471-0528.2010.02761.x. Epub 2010 Nov 4. Associations of gestational weight loss with birth-related outcome: a retrospective cohort study. Beyerlein A, Schiessl B, Lack N, von Kries R. PMID: 21054761

...DESIGN: Retrospective cohort study. SETTING AND POPULATION: Data on 709 575 singleton deliveries in Bavarian obstetric units from 2000-2007 were extracted from a standard dataset for which data are regularly collected for the national benchmarking of obstetric units...RESULTS: GWL was associated with a decreased risk of pregnancy complications, such as pre-eclampsia and nonelective caesarean section, in overweight and obese women [e.g. OR = 0.65 (95% confidence interval: 0.51, 0.83) for nonelective caesarean section in obese class I women]. The risks of preterm delivery and SGA births, by contrast, were significantly higher in overweight and obese class I/II mothers [e.g. OR = 1.68 (95% confidence interval: 1.37, 2.06) for SGA in obese class I women]. In obese class III women, no significantly increased risks of poor outcomes for infants were observed. CONCLUSIONS: The association of GWL with a decreased risk of pregnancy complications appears to be outweighed by increased risks of prematurity and SGA in all but obese class III mothers.

Epidemiology. 2006 Mar;17(2):170-7. Combined effects of prepregnancy body mass index and weight gain during pregnancy on the risk of preterm delivery. Dietz PM, Callaghan WM, Cogswell ME, Morrow B, Ferre C, Schieve LA. PMID: 16477257

...METHODS: Using data from the Pregnancy Risk Assessment Monitoring System in 21 states, we estimated the risk of very (20-31 weeks) and moderately (32-36 weeks) preterm delivery associated with a combination of prepregnancy body mass index (BMI) and gestational weight gain among 113,019 women who delivered a singleton infant during 1996-2001...RESULTS: There was a strong association between very low weight gain and very preterm delivery that varied by prepregnancy BMI, with the strongest association among underweight women (adjusted odds ratio = 9.8; 95% confidence interval = 7.0-13.8) and the weakest among very obese women (2.3; 1.8-3.1)...Women with very high weight gain had approximately twice the odds of very preterm delivery, regardless of prepregnancy BMI. CONCLUSIONS: This study supports concerns about very low weight gain during pregnancy, even among overweight and obese women, and also suggests that high weight gain, regardless of prepregnancy BMI, deserves further investigation.

J Matern Fetal Neonatal Med. 2012 Oct;25(10):1909-12. doi: 10.3109/14767058.2012.664666. Epub 2012 Mar 12. Gestational weight loss has adverse effects on placental development. Hasegawa J1, Nakamura M, Hamada S, Okuyama A, Matsuoka R, Ichizuka K, Sekizawa A, Okai T. PMID: 22348351

OBJECTIVE: To clarify whether mothers with gestational weight loss (GWL) were likely to have adverse effects on the placenta. STUDY DESIGN: Subjects who delivered viable singleton infants after 24 weeks of gestation were enrolled. A retrospective analysis to evaluate cases of GWL in association with the findings of the placenta and amniotic membrane after delivery was conducted. After consideration of confounders, a case-control study with matched pairs (1:2) was performed. RESULTS: Of all subjects (5551 cases), 83 cases (1.5%) with GWL were found. Since the pre-pregnancy maternal body mass index (BMI) was significantly higher in cases, 166 controls with a matched BMI were selected. The neonatal birth weights, placental weights and the umbilical cord length in cases were significantly smaller than in controls (p < 0.05). Preterm delivery and small for gestational age (SGA) infants were more frequently observed in cases compared with controls [odds ratio (OR) 6.3; 95% confidence interval (CI) 3.3, 12.1, OR 4.3; 95% CI 1.9, 9.9]. pPROM were observed in 10.8% of the cases and 1.8% of the control (OR 6.6; 95% CI 1.7, 25.1). However, the frequencies of chorioamnionitis and the cervical length at second trimester were not different between the two groups. CONCLUSION: GWL is associated with SGA, small placenta, short umbilical cord length, preterm delivery and pPROM.