ATLANTA (FRONTLINE MEDICAL NEWS) Both short and long sleep duration during pregnancy are associated with extremes of gestational weight gain, according to findings from a multicenter prospective cohort study.

Among 760 nulliparous women with a singleton gestation who were part of the nuMoM2b (Nulliparous Pregnancy Outcomes Study: Monitoring mothers-to-be) network – a National Institute of Child Health and Human Development cohort of more than 10,000 women – the 2.1% with average sleep duration of fewer than 6 hours and the 5.2% with sleep duration greater than 9 hours had the highest rates of low gestational weight gain (z less than –1). The differences were statistically significant, compared with those with average sleep duration of 7 to fewer than 9 hours, at visits between 16 and 21 weeks and between 22 and 29 weeks (P less than .0001, P = .04, respectively), Dr. Francesca Facco reported at the annual Pregnancy Meeting sponsored by the Society for Maternal-Fetal Medicine.

For example, at visit 2, the rate of low gestational weight gain was 18.8% and 35.5% for those with sleep duration fewer than 6 hours and more than 9 hours, respectively, vs. 8.2% for those with sleep duration of 6 to fewer than 7 hours, and 12% for those with 7 to fewer than 8 hours.

The differences were similar in magnitude at the last weight measure prior to delivery but did not reach statistical significance, said Dr. Facco of Magee-Women’s Research Institute, University of Pittsburgh.

“Nonlinear relationships were observed between sleep duration and gestational weight gain,” she said, adding that at all gestational weight gain assessments, high gestational weight gain occurred more frequently as sleep duration shortened.

“We found a U-shaped relationship between sleep and low gestational weight gain; women with the shortest and the longest sleep duration had the highest rates of low gestational weight gain,” she said.

The findings suggest that both long and short sleep duration are associated with extremes of gestational weight gain.

Study subjects were enrolled in the nuMoM2b study and were recruited at the second study visit (16-21 weeks) to wear an actigraph to measure sleep activity for 7 consecutive days. The women, who had a mean age of 27 years, also kept a sleep diary. A little over half (51.5%) were normal weight, 3% were underweight, and 45.5% were overweight or obese. Gestational weight gain was examined using age-standardized z scores, which are a measure of gestational weight gain uncorrelated with gestational age and body mass index.

Sleep is getting more and more attention as an important health behavior, especially in relation to weight and metabolism, Dr. Facco said, noting that short sleep duration has consistently been associated with higher body mass index, and studies show that short sleep duration hinders weight loss efforts.

Data on long sleep duration are less clear but suggest an age-dependent relationship, she said.

The current study was undertaken to evaluate whether the findings in nonpregnant women also apply during pregnancy.

Data from the same cohort, which were presented at the 2015 Pregnancy Meeting, showed that women with sleep duration of fewer than 7 hours had twice the rate of gestational diabetes, compared with those who slept 7 or more hours. The finding remained significant even after adjusting for age and body mass index. Those findings are congruous with the current findings, Dr. Facco said, explaining that the short sleepers were those most likely to have the greatest weight gain, thus putting them at higher risk of gestational diabetes.

“Poor sleep in pregnancy has been linked to adverse pregnancy outcomes, and this association between sleep and gestational weight gain suggests one possible mechanism for this association,” she concluded.

The nuMoM2b study is funded by the National Institutes of Health. Dr. Facco reported having no conflicts of interest.