Low Gestational Weight Gain and Risk of Adverse Perinatal Outcomes in Obese and Severely Obese Women

Abstract

Background Our objective was to estimate associations between gestational weight gain z-scores and preterm birth, neonatal intensive care unit admission, large- and small-for-gestational age birth (LGA, SGA), and cesarean delivery among grade 1, 2, and 3 obese women. Methods Singleton infants born in Pennsylvania (2003–2011) to grade 1 (body mass index (BMI) 30–34.9 kg/m2, n=148,335), grade 2 (35–39.9 kg/m2, n=72,032), or grade 3 (≥40 kg/m2, n=47,494) obese mothers were included. Total pregnancy weight gain (kg) was converted to gestational age-standardized z-scores. Multivariable Poisson regression models stratified by obesity grade were used to estimate associations between z-scores and outcomes. A probabilistic bias analysis, informed by an internal validation study, evaluated the impact of BMI and weight gain misclassification. Results Risks of adverse outcomes did not substantially vary within the range of z-scores equivalent to 40-week weight gains of −4.3 to 9 kg for grade 1 obese, −8.2 to 5.6 kg for grade 2 obese, and −12 to −2.3 kg for grade 3 obese women. As gestational weight gain increased beyond these z-score ranges, there were slight declines in risk of SGA but rapid rises in cesarean delivery and LGA. Risks of preterm birth and neonatal intensive care unit admission were weakly associated with weight gain. The bias analysis supported the validity of the conventional analysis. Conclusions Gestational weight gain below national recommendations for obese mothers (5–9 kg) may not adversely affect fetal growth, gestational age at delivery, or mode of delivery.

Body Composition During Pregnancy Differs by Obesity Class

“…In our study, maternal body size early in pregnancy was negatively associated with gestational weight gain, which is in line with epidemiological studies . The inverse association between body size and weight gain is postulated to reflect a biological adaptation of women with increased adiposity to minimize the risk for pregnancy complications and infant outcomes .…”

“…As we recently published , weight maintenance and hence fat loss in pregnancy would require a daily energy deficit of ~300 kcal/d or 10% dietary energy restriction across the second and third trimesters. Epidemiological studies have already suggested that a dietary energy deficit is required for women with obesity to minimize risk for gestational hypertension, high birth weight, infant mortality, and delivery complications . The long‐term effects of such approaches on fetal development remain to be determined.…”

“…The Institute of Medicine guidelines acknowledge that insufficient data prevented the current weight gain guidelines from providing independent weight gain recommendations for each obesity class. Since then, epidemiological studies have suggested the inverse association between maternal BMI and healthy weight gain observed in nonobese women also continues with obesity severity . Thereby, opposed to the 5‐ to 9‐kg weight gain currently recommended for all women with obesity, optimal pregnancy outcomes may require further weight gain restrictions for women with BMI greater than 35 and weight maintenance or even weight loss for women with BMI greater than 40.…”

Variability of Very Low Birth Weight Infant Outcome and Practice in Swiss and US Neonatal Units

“…Two recent retrospective studies, with >180 000 pregnancies each, have however found no adverse association between BMI and GA at delivery for preterm birth. 30,31 BMI-associated type 2 diabetes, however, is associated with adverse outcome of preterm birth. 32 Further differences for which we have no data available to measure an effect are smoking and alcohol consumption, both of which are higher in Switzerland.…”

Weight gain during pregnancy and the black-white disparity in preterm birth

“…6,7 In addition, our study clarifies prior mixed evidence that high weight gain is a risk factor for preterm birth in women of all BMI groups and that low weight gain is not a risk factor in obese women. 6-10,26 …”