Maternal and Neonatal Outcomes in Obese Women Who Lose Weight During Pregnancy

CM Cox Bauer; KA Bernhard; DM Greer; DC Merrill


J Perinatol. 2016;36(4):278-283. 

In This Article

Abstract and Introduction


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.


Obesity is the epidemic of the twenty-first century. It has been touted as the next great evil in health care, consuming 147 billion dollars in 2008 and increasing exponentially.[1] More than one-third (78.6 million) of US adults are obese, of which >31.9% are women of reproductive age.[1,2] In 2001 to 2002, 30.5% of US adults aged >20 years were obese, as compared with 34.9% in 2011 to 2012.[3] Previous research also demonstrates that minority populations are disproportionately affected by obesity, with 50% of African-Americans and 36% of Mexican-Americans being obese.[3] Obesity can impact a woman throughout her lifetime by increasing her risk for developing chronic medical conditions, including diabetes mellitus, hypertension, dyslipidemia, heart disease, stroke, sleep apnea and cancer.[4] Despite our knowledge of pervasiveness and impact, however, obesity in the United States continues to increase in prevalence and has become a leading cause of morbidity and premature mortality in women, contributing to nearly 112 000 excess deaths per year.[5]

Weight management during pregnancy represents an important topic in health-care research, as well as in discussions between providers and their patients. For women with obesity in particular, focus should also be given to neonatal and maternal morbidity and mortality risks associated with antepartum obesity. Elevated risk has been documented for gestational diabetes, preeclampsia, macrosomia, preterm birth, postterm birth, fetal death, cesarean delivery and multifetal gestations. Women with obesity are also at increased risk for infection, postpartum hemorrhage, unsuccessful breastfeeding, increased risk of venous thromboembolism and increased risk of birth control failure.[6] Finally, the level of weight gained during pregnancy can have a major role in determining whether or not a woman will return to her prepregnancy weight.

Appropriate weight gain during pregnancy is controversial in the obese population. The Institute Of Medicine (IOM) recommends that a woman with obesity, or body mass index (BMI) ≥30 kg m 2, gain 11 to 20 pounds during her pregnancy.[7] However, this recommendation may be unsatisfactory when considering the conflicting results of previous studies and limited evidence of improved outcomes. For instance, recent research suggests that obese women who gain weight in agreement with IOM recommendations, compared with those with excessive weight gain, do not incur increased risk for low birth weight or small-for-gestational age infants but benefit from decreased risk for large-for-gestational age infants.[8–12] Evidence also exists to suggest that weight loss in obese pregnant women decreases risk for preeclampsia and cesarean delivery.[13] Furthermore, research on fetal outcomes suggests that women with obesity who gain below IOM recommendations experience lower risk for neonatal intensive care unit (NICU) admissions than women who lose weight.[13]

Without convincing evidence of improved outcomes for women with obesity, numerous health-care professionals may find great difficulty in recommending that a woman gain up to 20 pounds when already above her ideal body weight.[14] For this reason, the goal of our study was to examine the validity of the IOM guidelines and provide recommendations for maintenance or change of the guidelines. To accomplish our goal, we conducted a retrospective study with matched-subjects design to examine patterns in maternal and neonatal outcomes across loss, maintenance, appropriate gain and excessive gain categories of weight change for women with obesity.