Pregnant women are often advised to sleep on their left side to avoid complications. Past studies have suggested that sleeping on the back or the right side could have a bad effect on blood flow from the blood vessels to the uterus.

A new U.S. prospective study published this month in the journal Obstretics & Gynecology, states that different sleep positions do not increase the risk of complications during the first 30 weeks of pregnancy.

These retrospective studies were done in small groups of women and after a stillbirth, which increases the chance of bias.

According to author Dr. Robert Silver of the University of Utah School of Medicine, the advice to sleep on the left side alone could cause unnecessary anxiety in women. Even when such advice is given carefully, it can lead to sleep deprivation, feelings of guilt and shame when something does happen.

Silver et al. investigated the dates of 8709 women who were pregnant with their first child. They were asked about their sleeping habits during the first 30 weeks of their pregnancy. In addition, the sleeping positions of one third of the women were objectively recorded by means of video cameras. In the study group 22% of the women later experienced complications, such as stillbirth, high blood pressure and low birth weight. However, no link was found between these pregnancy complications and the sleeping positions. Other factors, such as obesity and smoking, did increase the risk of complications. Sleeping positions during the last part of the pregnancy were not investigated.

In summary: women should sleep in a position that is most comfortable for them.

Source: Silver, R.M., Hunter, S., Reddy, U.M., Facco, F., Gibbins, K.J., Grobman, W.A., ... Study, O. (2019). Prospective Evaluation of Maternal Sleep Position Through 30 Weeks of Gestation and Adverse Pregnancy Outcomes, 00(00), 1–10.