Although doctors often tell pregnant women it’s safest to sleep on their left side, a new study suggests sleeping in other positions may not be a problem.
Researchers examined data on outcomes for 8,709 pregnant women who completed at least one sleep questionnaire before they reached 30 weeks’ gestation. Overall, 1,903 women, or 22%, experienced serious complications like dangerously high blood pressure, stillbirth or a newborn small for its gestational age.
Women who slept on their right side or on their back were no more likely to experience serious complications than women who slept on their left side, the study found.
These results should reassure many pregnant women who might worry about harming their baby by sleeping on their back, or moving into this position during the night, said Dr. Robert Silver, lead author of the study and chair of obstetrics and gynecology at the University of Utah School of Medicine in Salt Lake City.
“There is downside to encouraging the avoidance of supine (back) sleep,” Silver said by email.
“Some women may have trouble sleeping on their left side and they cannot control movement during sleep,” Silver added. “Even with careful messaging, there is potential to increase anxiety in women who wake up on their backs and guilt, shame and self-blame in women suffering adverse pregnancy outcomes such as stillbirth.”
Previous studies have linked sleeping on the back or right side to an increased risk of serious pregnancy complications because these positions may compress blood vessels supplying the uterus, researchers note in Obstetrics and Gynecology.
Women in the current study were more likely to have serious pregnancy complications when they were overweight or obese, smoked or had high blood pressure or diabetes prior to pregnancy.
Neither the positions women were in when they went to sleep or woke up, nor the positions they might move to during the night appeared to impact the risk of complications.
Researchers also looked at objectively-measured sleep positions for a subset of women who underwent home sleep studies for nighttime breathing problems. For these women, there also was no meaningful difference in the risk of pregnancy complications based on whether they slept on their back more than half of the time, or less often.
The study wasn’t designed to prove whether or how sleep positions might directly impact pregnancy outcomes. It also didn’t look at the connection between sleep position and complications in the final weeks of pregnancy.
One limitation of the study is that there were only about a dozen stillbirths – which may have been too few to detect meaningful differences in this outcome based on sleep position, the study team notes.
Even so, women should be reassured by the results, said Dr. Nathan Fox, a clinical professor at the Icahn School of Medicine at Mount Sinai and vice president at Maternal Fetal Medicine Associates in New York City.
“Pregnant women should sleep in the position that they find most comfortable,” Fox, who co-wrote an editorial accompanying the study, said by email. “For the few that do experience complications of pregnancy they should be reassured that it was not due to their sleeping position.”
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