Weight loss in obese pregnant women and risk for adverse perinatal outcomes.

OBJECTIVE: To examine the association between weight loss in obese pregnant women and relevant maternal and neonatal outcomes.

METHODS: All liveborn singleton term (37 weeks of gestation or greater) births in obese women between 2009 and 2011 in Flanders (the northern part of Belgium) were included (N=18,053). Outcomes assessed included gestational hypertension, low (2,500 g or less) birth weight, small-for-gestational-age (less than the 10th percentile) neonates, macrosomia (birth weight 4,000 g or greater), large-for-gestational-age (greater than 90th percentile) neonates, emergency caesarean delivery, and admission to a neonatal intensive care unit. Risk for adverse outcomes was calculated by multiple logistic regression analysis for weight change categories (greater weight loss [5 kg or greater], lesser weight loss [between 0 and 5 kg], low gestational weight gain [0 or greater and less than 5 kg], adequate gestational weight gain [5 or greater to 9 kg or less, reference], and excessive gestational weight gain [greater than 9 kg]) in each obesity class (I 30-34.9, II 35-39.9, III 40 or greater) adjusted for parity and maternal and gestational age.

RESULTS: In the total population, 854 (4.7%) obese pregnant women reported weight loss. Weight loss and low weight gain were associated with a decreased incidence of gestational hypertension for women with class I obesity (greater weight loss adjusted odds ratio [OR] 0.31, 95% confidence interval [CI] 0.11-0.84; lesser weight loss adjusted OR 0.46 95% CI 0.21-0.99; low gain adjusted OR 0.71 95% CI 0.54-0.93), a reduction in the rate of emergency cesarean delivery, but only in those with class II obesity (greater weight loss adjusted OR 0.24, 95% CI 0.07-0.78; lesser weight loss adjusted OR 0.50, 95% CI 0.26-0.97; low gain adjusted OR 0.55, 95% CI 0.38-0.79), and decreased macrosomia and large-for-gestational-age neonates in women in all classes of obesity, with the highest decrease for women with class III obesity (greater weight loss adjusted OR 0.15, 95% CI 0.05-0.49; lesser weight loss adjusted OR 0.37, 95% CI 0.15-0.90 for macrosomia). No association between weight loss and low birth weight, small-for-gestational-age neonates, or admission to the neonatal intensive care unit was shown in the different obesity classes.

CONCLUSION: Weight loss in obese pregnant women was associated with reduced perinatal risks but not with the rate of low birth weight or small-for-gestational-age neonates in obese women from class III in this affluent region. Stratification of recommended gestational weight gain ranges in obese women should be considered.

LEVEL OF EVIDENCE: II.