Gestational weight gain linked to increased infant morbidity and mortality

Inadequate gestational weight gain (GWG) was linked to increased risks of adverse infant outcomes in the United States, even for obese women, according to a retrospective cohort study in JAMA Network Open.¹

The study used data sets from the National Center for Health Statistics database from 2011—the year maternal weight and height were first reported—to 2015 (the latest available year), for a total of 15,759,945 mother-infant dyads.

The study was confined to singleton births and excluded post-term births. The mean maternal age was 28.1 years. Body mass index (BMI) was calculated as prepregnancy weight in kilograms (kg) divided by height in meters squared.

BMI was then categorized into 6 groups, according to the World Health Organization classification.

For the study, 4% of women were underweight (less than18.5 kg); 47% normal weight (18.5 kg - 24.9 kg); 25.3% overweight (25 kg - 29.9 kg); 13.2% class 1 obesity (30 kg - 34.9 kg); 6.2% class 2 obesity (35 kg -39.9 kg); and 4.3% class 3 obesity (≥40 kg).

Women gained a mean 14.1 kg during pregnancy, while the mean GWG decreased with increasing BMI categories: a decrease of 15.7 kg for underweight, 15.4 kg for normal weight, 14.2 kg for overweight, 12.2 kg for obesity class 1, 10.3 kg for obesity class 2, and 8.2 kg for obesity class 3 (P < 0.001 for trend).

Overall, 8.8% of newborns had significant morbidity, with the lowest prevalence of 8% among infants delivered by women in the normal weight BMI class and the highest of 12.4% among infants delivered by women with class 3 obesity.

In addition, 0.34% of infants died within 1 year of birth, with the lowest prevalence of 0.28% among infants delivered by women in the normal weight BMI class and the highest of 0.58% among infants delivered by women with class 3 obesity.

The absolute risks of infant morbidity and mortality were lowest in the middle groups of GWG.

Conversely, infant morbidity was more likely in the lowest GWG groups of underweight women (<8 kg GWG) and in normal-weight women (<0 kg GWG): 14.7% and 16.6%, respectively.

But infant morbidity was most prevalent in the highest GWG groups of obese women: 15.2% for obesity class 1 (≥30 kg GWG), 13.7% for obesity class 2 (≥20 kg GWG), and 17.4% for obesity class 3 (≥20 kg GWG).

Optimal GWG ranges were 12 kg to less than 24 kg for underweight and normal-weight women, 10 kg to less than 20 kg for overweight women, 8 kg to less than 16 kg for women with class 1 obesity, 6 kg to less than 16 kg for class 2 obesity, and 6 kg to less than 10 kg for class 3 obesity.

The lower bounds of the optimal GWG ranges seemed to be higher than the existing recommendations for overweight women (10 kg vs 7 kg) and those with class 1 obesity (8 kg vs 5 kg), class 2 obesity (6 kg vs 5 kg), and class 3 obesity (6 kg vs 5 kg).

“The results suggested that weight maintenance or weight loss should not be used as routine guidelines,” The authors concluded.

__

Reference

1. Wang L, Zhang X, Chen T, et al. Association of gestational weight gain with infant morbidity and mortality in the United States. JAMA Netw Open. Published online December 1, 2021. doi:10.1001/jamanetworkopen.2021.41498The