Can I sleep on my back in pregnancy?

Many pregnant women are concerned and have been told, or have read, that it is dangerous to sleep or lie on their back in pregnancy. This is a particular concern if a woman is used to sleeping on her back as it is more comfortable and if she wakes to find she has been sleeping on her back.

The anxiety about this is huge for so many women. I have patients in their first trimester of pregnancy who tell me they have woken from their sleep on their back and have been concerned they have harmed their baby.

The background of the concern is in advanced (third trimester) pregnancy the considerable weight of the large size of the uterus may compress blood vessels supplying the uterus and potentially harm the fetus. There have been studies there this been associated with increased risk of stillbirth and intrauterine foetal growth retardation. It has been concluded in these studies that this risk can be reduced of a woman sleeps on her side in advanced pregnancy.

The association between sleep position and stillbirth risk is a complex issue and is not universally agreed (1)

A challenge is there are stillbirth risk variables that have not been reported in many studies. Gordon et al report (2) “We postulate that our findings indicate supine sleep position may be an additional risk for a vulnerable fetus. Other risk factors identified were suspected fetal growth restriction, not being in paid work, and lower educational status. This study suggests that supine sleep position may be an additional risk for late-pregnancy stillbirth in an already compromised fetus. The clinical management of suspected fetal growth restriction should be investigated further as a means of reducing late stillbirth.”

Warland et al report (3) “Our model for late unexplained stillbirth is that it results from the intersection of: 1) maternal factors (such as maternal age, obesity, smoking), 2) fetal/placental factors (such as intrauterine growth retardation, placental insufficiency), and 3) a fetal stressor (such as venocaval compression from maternal supine sleep position, sleep disordered breathing). Death occurs only if all three factors intersect and only if the stressor and maternal factor match the specific vulnerability of the individual fetus.”

Sleep position concern can increase pregnancy anxieties. A pregnant woman is frightened to go to sleep in case she rolls onto her back while asleep. This fear can detract from a woman’s enjoyment of her pregnancy. As well, with a large pregnant uterus, a woman can find it difficult to find a comfortable position while asleep. It is common for people to change position while asleep and I suspect it is more so for woman in advanced pregnancy.

A recent study (4) found self-reporting of position when sleep was not always accurate. For those who do not ordinarily sleep on the left side, asking participants to sleep on their left may result in reduced sleep duration. This is an important consideration during a sleep-critical time such as late pregnancy and can adversely affect woman’s wellbeing.

If a woman does tragically have stillbirth, she may blame herself and her sleeping position for her pregnancy loss, even if she endeavoured to sleep on the left side.  In my experience the reason for stillbirth can usually be seen at delivery or in the autopsy. This is not consistent with sleeping position being a common cause. Cronon et al report (5) after studying results of six case-control studies that late stillbirth incidence is reduced by 5.8% if every pregnant woman ≥ 28 weeks’ gestation settled to sleep on her side.

Anderson et al report  (6) supine position sleeping is associated with intrauterine foetal growth retardation. “women at 28 weeks’ gestation or more who usually went to sleep in a supine position gave birth to infants with significantly lower mean birth weights (3410 g vs 3554 g for non-supine sleep)” As well  they found “no difference in stillbirth risk between left side and other non-supine going-to-sleep positions.”

There is no medical study-based evidence that there is any potential risk to the unborn baby if a pregnant woman sleeps on her back other than when she is in advanced (third trimester) pregnancy. Yet I am finding that women in early pregnancy have extrapolated this sleeping position fear to mean that at any gestation a woman cannot sleep on her back. Such illogical thinking only heightens a woman’s pregnancy anxieties.

A recent large prospective study (7, 8) co-authored by 18 doctors in USA concluded: “Going to sleep in the supine or right lateral position, as self-reported before the development of pregnancy outcome and objectively assessed through 30 weeks of gestation, was not associated with an increased risk of stillbirth, a small-for-gestational-age newborn, or gestational hypertensive disorders.” 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, who co-wrote an editorial accompanying the study stated: “Pregnant women should sleep in the position that they find most comfortable.”  “For the few that do experience complications of pregnancy they should be reassured that it was not due to their sleeping position.”

It is common when a woman is in first stage labour for her to lie on her back in a semi recumbent (Fowler’s position), as it is often the most comfortable position in first stage labour. When she is pushing in second stage labour it is common for a woman to be on her back in a dorsal recumbent position with her hips and knees flexed (held back by her hands behind her thighs) and neck flexed, as this is often the most efficient position for her for pushing in second stage labour. There is foetal heart monitoring and usually the baby’s heart rate pattern is normal indicating good oxygenation of baby in labour even though she is in a supine position. If the foetal heart rate pattern becomes abnormal then she is repositioned to her lie on her side. If she is repositioned to her left side and there is still concern, she is switched to lying on her right side. The concern is about umbilical cord compression which can be related to her position.  I recently delivered a patient where the foetal heat rate pattern was abnormal when she was lying on both her left and her right sides but was normal when she was on her back.

For some women in advanced pregnancy to lie on their back will can result in her becoming light-headedness, dizziness and possibly in breathlessness. If this does happen a woman will know not to lie on her back.

What can be done about it?

Sleeping On Your Back During PregnancyThere is no risk you or baby if your sleep on your back or in any position other than in advanced (third trimester) pregnancy.

There is some increase in the risk of stillbirth if you sleep on your back in advanced pregnancy, especially if there are maternal risk factors (such as maternal age, obesity, smoking) and fetal/placental risk factors (such as intrauterine growth retardation, placental insufficiency).

You should avoid sleeping on your back in advanced pregnancy if your baby is growth retarded.

If you do find yourself sleeping on your back don’t be overly concerned as late stillbirth incidence is reduced by only 5.8% when you sleep on your side.

Although it is stated you should sleep on your left side, studies have not confirmed which side you sleep on is relevant.

If unwell when on your back then you will want to avoid lying on your back. Usually by lying on your right or left side or being more in an upright position will make you feel better.









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