Weight Loss In Pregnancy Doubles the Risk for Low Birth Weight Babies

Here is yet another study showing that weight loss during the pregnancies of "obese" women increases the risk for low-birth weight babies.

In this study, weight loss during pregnancy doubled the risk for a low-birth-weight baby. 

This is important because low-birth-weight babies are at increased risks for health problems as they get older, including insulin resistance, diabetes, abdominal fatness, metabolic syndrome, and cardiovascular disease. In the rush to "cure" obesity through restricted prenatal weight gain, are care providers increasing the next generation's risk for the very conditions they are trying to prevent?

Nor is this the first study to find an increased risk for small-for-gestational-age babies with gestational weight loss. It is only the latest of quite a few to find this. One recent systematic review concluded that Gestational Weight Loss "should not be advocated in general for obese women."

Yet there are still care providers who are pressuring women of size to lose weight during pregnancy. Care providers need to STOP promoting gestational weight loss as a goal for obese women. 

Side Notes and Cautions

A couple of cautions about the study. 

As we discussed before, there are women of size who naturally lose weight in pregnancy because their metabolism increases during pregnancy. This doesn't automatically mean a bad outcome, and no one should panic if they are losing weight without trying. Some women, especially those with higher BMIs, lose weight without restricting their nutrition and have perfectly fine outcomes. As long as you are eating well and baby seems to be growing adequately, it's not something to panic about. 

But deliberately trying to lose weight during pregnancy is a different story. The care providers who are pressuring women to lose weight during pregnancy by restricting their intake or eliminating food groups are putting babies at risk and this study confirms that. 

Care providers should NOT be counseling women to gain no weight or to lose during pregnancy. Previous research shows that this is particularly risky for women in the "overweight" (BMI 25-30) and "borderline" obese (BMI 30-35) groups. Some gain seems to be helpful, even if the overall gain in higher BMI women is lower than in other weight groups.

On the other hand, it is important to note that excessive weight gain also is associated with increased risks, most notably for a big baby. (It is also associated with higher rates of blood pressure issues in pregnancy, although this could simply be coincidental due to fluid retention.) 

This means that women of size should try to avoid a too-high gain if they can. However, plenty of high-BMI women have had higher gains and still had healthy outcomes. Like weight loss, a higher gain is not something to aim for, but it doesn't have to be something to panic over either, as long as nutrition is normal and healthy and baby seems to be growing along a normal curve.  

Moral of the story: High-BMI women have the best outcomes in pregnancy when they gain modestly...not too much but not losing either. 

However, a modest gain with good nutrition is different from manipulating weight gain deliberately by restricting calories. In my opinion, it's far better to focus on optimal nutrition than on trying to manipulate weight gain to meet arbitrary weight gain guidelines.

My Biggest Quibble

I am always disappointed that I have yet to see a prenatal weight gain study that focuses on the right issue ─ nutrition. Instead they use weight gain as a proxy for good nutrition, which is an erroneous thing to do. 

A person who gains 11-20 lbs. (the amount recommended for obese women by the Institute of Medicine guidelines) while eating a lot of junk food probably has a lot different outcome than one who gains the same amount from healthy proteins, whole grains, and a variety of fruits and vegetables. Both gains are the same, but the nutrition is very different. Instead of looking only at how much weight women gain, I'd rather they did a more qualitative investigation into what the women were consuming and how that influenced outcomes. 

I'd personally be a lot less worried about the woman of size who gains 30 lbs. while eating an excellent diet than one who gains 30 lbs. from eating Twinkies and ice cream. I'd also be a lot less worried about one who loses weight in pregnancy while eating a healthy diet with plenty of calories than one who loses weight by drinking Slim-Fast to limit her weight gain. (Yes, sadly, that's a real recommendation from a real doctor.)

Rather than obsessing over weight gain, care providers would do better to focus on the quality of the mother's nutrition rather than obsessing so much about the numbers on a scale. 

Reference

J Perinatol. 2016 Jan 7. doi: 10.1038/jp.2015.202. [Epub ahead of print] Maternal and neonatal outcomes in obese women who lose weight during pregnancy. Cox Bauer CM1, Bernhard KA2,3, Greer DM2,3, Merrill DC1. 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. Using a 1:1:1:1 design (n=778 matched groups), we matched women with obesity who lost, maintained, gained appropriate (IOM recommended) and gained excessive weight during pregnancy by gestational age at delivery, maternal age, race/ethnicity, prepregnancy BMI, chronic hypertension, pregestational diabetes and smoking status. Regression techniques were used to adjust for confounders and compare outcomes across weight change categories. 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. From lost to excessively gained weight, the odds of cesarean delivery increased 1.4 times and mean infant birth weight increased by 197 g. In contrast, the odds of small-for-gestational age were 1.8 times greater for women who lost than gained excessive weight. CONCLUSION: Weight loss in obese pregnant women is associated with increased risk for low birth weight neonates but significantly decreased or maintained risk for other maternal and neonatal morbidities, as compared with appropriate or excessive weight gain. This study supports re-evaluation of the current IOM guidelines for women with obesity.