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


As the prevalence of obesity continues to increase in the United States, appropriate weight gain recommendations during pregnancy will become increasingly important. Likewise, adherence to these recommendations will be essential for minimizing maternal and neonatal morbidity in the obese population. In 2009, IOM guidelines for gestational weight gain were developed with a principal focus of reducing small-for-gestational age infants, and weight gain below recommended levels has since shown to increase risk for small-for-gestational age infants in normal weight and overweight women.[18–21] However, these guidelines did not account for other sources of maternal and infant morbidity and mortality and also did not evaluate obese women. Although some studies support IOM recommendations for gestational weight gain in women with obesity, evidence also exists to refute the recommendations.[12,13,20,22–24] New information put forth in the literature are inconsistent and thus collectively inconclusive, with recommendations ranging from a lowered level of weight gain between 4.5 and 11 kg (10 to 25 pounds) to weight maintenance in women with BMI>40 kg m−2 and weight loss in those who are super morbidly obese.[13,20,22,23,24]

In comparison with findings from the limited literature on women and weight loss, our study is distinctive in that we examined the maternal and neonatal outcomes associated with weight change in patients carefully matched across four weight change categories. In our investigation of >10 000 total women with obesity and 3112 women in 778 groups matched across weight gain categories, we detected minimal neonatal and maternal morbidity with maternal weight loss or maintenance. In fact, adverse outcomes for women who failed to reach the IOM recommendations were strictly related to neonate weight, including reduced infant birth weight and increased odds of low birth weight infant. Odds of small-for-gestation age infant did not significantly differ between women who lost weight and those who gained appropriate weight, but they were greater for the former than women who gained excessive weight. Consistent with earlier reports, a possible trend toward increased odds of preterm birth with weight loss was suggested, but the association was not statistically significant.[20,22,23–26] Moreover, the preterm birth rate in all weight change categories never exceeded the national prevalence rate of 11.38%.[26]

Importantly, as compared with women who achieved IOM recommendations, women in the lost and maintained weight categories did not show significantly greater risk corresponding to any of the maternal and neonatal outcomes studied, except infant birth weight. For these women, we did not observe more cesarean deliveries or NICU admissions nor did we observe greater prevalence of gestational hypertension or preeclampsia, gestational diabetes, low cord pH or low 5-min APGAR scores. We did observe, however, significantly less estimated blood loss for women who lost or maintained weight. Furthermore, trends of increased risk with increasing weight gain and significant differences between weight change categories suggested that women who gained excessive weight incurred the greatest risk for maternal and neonatal morbidities, including cesarean delivery, gestational hypertension/preeclampsia, macrosomia, low 5-min APGAR score and greater estimated blood loss. Our findings are consistent with some earlier reports on pregnancy in women with obesity,[13,15,22,27] suggesting that significant improvements may be realized in neonatal and maternal outcomes by using weight recommendations less than included in the current IOM guidelines.

Our study results also have important public health implications for long-term health of obese women. Not only does our study confirm the results of some prior studies and add to the growing base of evidence that lower weight gain recommendations are appropriate for obese women but it also may aid in counseling on appropriate weight management during pregnancy. As women with higher weight gain during pregnancy are known to incur greater risk of increased weight retention at 18 months postpartum, it may be reasonable to recommend lower weight gain limits for obese women.[28] Weight loss in our population was modest, with an average of 7.2 pounds at delivery. However, considering weight of the fetus, placenta and fluid (which totals approximately 10 to 12 pounds), total weight loss by the mother of approximately 18 to 20 pounds is attained in these pregnancies.[29] This equates to a significant decrease in BMI, thereby reducing the long-term health consequences of the mother. For women with obesity who are motivated to continue a healthy lifestyle throughout their pregnancy, weight loss may be acceptable with minimal neonatal morbidity. Secondary to the increased risk of low birth weight and small-for-gestational age infants, it could be argued that these women would benefit from fetal growth ultrasounds to insure appropriate growth and adjust the mother's diet as appropriate, if complications appear.

Strengths of our study include the large, population-based cohort, which allowed for a large number of matched groups and a comprehensive match of patient characteristics across weight change categories. Our study also encompassed a diverse patient population, originating from 12 hospitals distributed across an expansive geographic area. Diverse patient characteristics coupled with a high degree of internal replication increases the generalizability and overall relevance of our study findings to other similarly structured regional or subcontinental populations. Our study also has limitations. First, the study was retrospective, and therefore, weight loss intent was not identifiable or controlled. Second, all weight data were obtained from an institutional database, which is populated by both staff and patients who report on essential data elements at the time of delivery. Moreover, our study also used patient-reported prepregnancy weights for those patients who did not receive prenatal care and whose medical records were unavailable. Use of such data reporting and collection methods increases potential for misreporting bias. Self-reporting of prepregnancy weight, however, has been validated previously in large studies, which showed no statistical difference between BMI categories based on patient-reported prepregnancy weights and those based on actual weights recorded in medical centers.[30]

In conclusion, our study suggests that the IOM recommendation of weight gain in obese pregnant women should be re-evaluated. In our patient population, benefits were obtained from weight loss and maintenance during pregnancy, but women of excessive weight gain exhibited greater risk for adverse maternal and neonatal outcomes.