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Managing Obesity During Pregnancy


Obesity is a worldwide epidemic with management implications that are more urgent than ever for obstetrics. The latest data from the Centers for Disease Control and Prevention show a prevalence of obesity that surpasses 35% in U.S. women of reproductive age.

Implications of Obesity

The potential maternal, fetal, peripartum, and neonatal complications in our obese pregnant patients are numerous. Studies have shown that the obese woman has a significantly increased risk of early miscarriage (an odds ratio of 1.2) and recurrent miscarriage (OR of 3.5), compared with a normal-weight woman after natural conception (Hum. Reprod. 2004;19:1644-6). The risk of congenital anomalies also rises in obese women. In a recent meta-analysis, obese mothers were at significantly increased risk of having a child affected by a neural tube defect (OR 1.9), spina bifida (OR 2.2), cardiovascular anomalies (OR 1.3), and other anomalies, compared with body mass index (BMI)–appropriate mothers (JAMA 2009;301:636-50). In a prospective, multicenter study of more than 16,000 women, obese women and morbidly obese women were 2.5 and 3.2 times, respectively, more likely to develop gestational hypertension than nonobese women. They also were 1.6 and 3.3 times more likely, respectively, to develop preeclampsia. Gestational diabetes was 2.6 and 4 times more likely to occur in obese and morbidly obese women, compared with normal-weight pregnant women (Am. J. Obstet. Gynecol. 2004;190:1091-7).

Obesity also increases the risk of indicated preterm delivery, caused by complications such as preeclampsia and diabetes. The risk of cesarean delivery and associated morbidities increases as well, as does the risk of macrosomia and fetal overgrowth (an increase in adipose tissue rather than lean body mass).

Macrosomia then perpetuates the problem of obesity in the offspring. Evidence clearly points toward an increase in adolescent and adult obesity in infants who are born either large for gestational age or who are macrosomic.

Excess maternal weight gain, particularly in average-weight women, is also a risk factor for excess birth weight (Obstet. Gynecol. 2008;112:999-1006).

There has been increasing awareness over the past decade, moreover, of the role that maternal obesity may play in unexplained antepartum fetal death. At least two studies—one in a Canadian population and one in a Danish National Birth Cohort — have shown that maternal pregravid weight increased the risk of unexplained fetal death, even in women without medical or obstetric complications (Obstet. Gynecol. 2000;95:215-21, and Obstet. Gynecol. 2005;106:250-9).

Managing the Obese Patient

Vigilant management of the obese pregnant woman is critical not only for the woman and her baby, but for future generations as well. We must increase our attentiveness to and surveillance for all the risks that obesity poses during pregnancy, and must think preventively during comprehensive preconceptional and postpartum care, with the goal of breaking the vicious cycle of obesity.

Until we gain a better understanding of underlying genetic predispositions, physiology, and mechanisms relating to maternal and fetoplacental interactions that affect fetal growth and development, all treatments in obese pregnant women must be empiric. However, we need to build upon the information we currently possess because waiting may not be an option.

Here are some of the key components of effective obesity management in pregnancy:

Appreciate that obesity is treatable. Certainly, women should aim to conceive while at a normal body mass index (BMI). Our ability to manage obesity preconceptually is constrained by the fact that many pregnancies are unplanned. However, when given the opportunity, we must encourage and help facilitate weight loss before pregnancy.

With proper counseling, some obese women can indeed achieve meaningful weight loss before conception. We know that lifestyle measures involving both nutritional counseling and exercise are more beneficial than either approach alone. The American College of Obstetricians and Gynecologists has practical guidelines on how to assess and manage obesity in the nonpregnant woman (“The Role of the Obstetrician Gynecologist in the Assessment and Management of Obesity,” Committee Opinion Number 319, October 2005).

We also must treat obesity as a problem itself, with an individualized, patient-centered approach. This point was stressed in the report on weight gain in pregnancy issued last year by the Institute of Medicine and National Research Council (

As obstetricians we tend to home in during pregnancy on the complications of obesity while overlooking the underlying problem. We also are less likely to think about individualized, patient-centered treatment for a woman who is overweight or obese as we would for a woman with a more straightforward problem like gestational diabetes. We need a change of mind set.

If a woman enters pregnancy obese, limiting her weight gain to recommended levels will help lower her risk of various complications and reduce postpartum weight retention. Exercise and other lifestyle changes will also improve insulin use in women with diabetes.


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