Sleeping well can be difficult during pregnancy, especially in the final months. New research suggests that poor sleep late in pregnancy may also be linked to how children grow during their first 2 years of life.
Researchers followed 645 mother-child pairs in Los Angeles and found that children whose mothers reported the poorest sleep late in pregnancy tended to weigh slightly less during their first 6 months, then gain weight more quickly. By about age 1, they weighed more on average than children whose mothers reported relatively good sleep. The study was observational, so it cannot show that poor sleep caused those differences or that the children will later develop obesity.
The study, published in the American Journal of Preventive Medicine, used data from the MADRES pregnancy cohort, which largely includes lower-income Hispanic families in Los Angeles.
Women completed a sleep questionnaire late in pregnancy, at an average of about 32 weeks. It asked about common sleep problems, including trouble falling asleep and waking during the night. About 26% of the women met the study’s definition of poor sleep quality.
The questionnaire did not measure exactly how long the women slept or identify specific problems such as sleep apnea. It also relied on women remembering and reporting their own sleep rather than using a wearable device or sleep study.
Researchers then tracked the children’s weight and length from birth through age 2 using medical records and measurements taken during study visits.
The biggest differences appeared among children whose mothers reported the worst sleep. Compared with children whose mothers reported relatively good sleep, they weighed less early in infancy but were heavier from roughly 11 to 22 months.
At age 1, the estimated difference was about 347 grams, or about three-quarters of a pound. At 17 months, when the gap was largest, it was about 752 grams, or 1.7 pounds.
The pattern was clearer among boys and among children born at term. Among boys, the average difference between about 11 and 21 months was roughly 651 grams, or 1.4 pounds. The association was less clear among girls and children born prematurely. Only 56 children in the study were born preterm, however, making that comparison less certain.
The researchers tried to account for several other factors that might influence a child’s growth, including the mother’s age and prepregnancy BMI, education, previous pregnancies, whether the child was born preterm and the child’s sex.
They also looked at whether breastfeeding, early introduction of food or juice, prenatal depressive symptoms or the timing of the sleep survey changed the findings. The overall pattern remained similar.
But no observational study can account for everything.
The researchers did not have enough information to fully consider factors such as what mothers ate during pregnancy, sleep disorders including sleep apnea, children’s diets and sleep habits, physical activity, parenting practices or broader sources of stress. The authors specifically caution that the results should not be interpreted as proof that poor sleep caused the differences in children’s growth.
Sleep may also overlap with other challenges during pregnancy. Nearly half of the women in the group reporting the poorest sleep had symptoms suggesting depression, compared with about 18% of those reporting the least sleep disturbance.
Accounting for prenatal depressive symptoms did not substantially change the results. Still, the researchers acknowledge that poor sleep could partly reflect broader stress or health challenges during pregnancy rather than acting on a child’s growth by itself.
Why does a difference in early weight gain matter?
Previous studies have linked unusually rapid weight gain during infancy with a higher likelihood of overweight or obesity later in childhood. But the researchers caution that there is no established cutoff showing that the weight differences seen in this study are harmful. They also followed the children only through age 2, so they could not determine whether the growth pattern continued as the children got older.
That distinction is important. This study did not find that poor sleep during pregnancy causes childhood obesity. It found a connection between mothers’ reported sleep quality late in pregnancy and the way their children gained weight during their first 2 years.
The researchers discuss several possible explanations, including changes in maternal health and stress during pregnancy, but those ideas were not directly tested.
“Poor sleep health in pregnancy is common and often overlooked, and our findings suggest that monitoring it in routine prenatal care could be a simple and powerful step toward healthier growth for the next generation,” lead author Xiaoran Yang said in the news release.
For now, the study adds to evidence that sleep may be an important part of pregnancy health. More research will be needed to determine whether improving sleep during pregnancy actually changes children’s growth or their chances of developing obesity later.
The study was supported by grants from the National Institute of Environmental Health Sciences, National Institute on Minority Health and Health Disparities, Southern California Environmental Health Sciences Center and the National Institutes of Health Environmental influences on Child Health Outcomes program.