Pregnant? We have good news!
Obstetrics & Gynecology, the go-to journal for our little niche in medicine, recently published new findings on sleep position in pregnancy.
For years and years we have been telling patients to sleep on their sides, left side more than right if you can tolerate it, because older studies suggested an increased stillbirth rate for those that did not.
Well, now a new study was just published, and I think you will like the results.
These older studies were retrospective studies, meaning they asked participants about their sleep habits AFTER they had a bad outcome to their pregnancy.
Thus, there was the possibility of what we call recall bias in the studies. As you can imagine, when someone has such a terrible loss in their life, they may remember habits (in this case sleep habits) that they have heard can lead to stillbirth.
As a result, these studies all showed a slight increased stillbirth risk of back and right sided sleepers, compared to left sided sleepers.
In addition, the physiology of the human body has compounded our sleep recommendations.
The pregnant uterus can push on the vena cava (the largest vein that brings blood back to the heart), thus reducing the amount of blood coming to the maternal heart, and subsequently leading to reduced fetal oxygenation.
In addition, for pregnant women who have a sleep disorder already (e.g. sleep apnea), sleeping on one’s back can worsen this.
Because stillbirth is such a devastating pregnancy outcome, it seems reasonable to change easily-modifiable behaviors (e.g. sleep) that could decrease that risk.
However, when we (obstetricians) make blanket recommendations on sleep positions there can be consequences.
Some women just cannot sleep in certain positions, or cannot control how they move at night. This, like most things in pregnancy, can lead to increased anxiety, self blame, and guilt.
Enter the new study.
It tracked over 8500 participants, and had them complete sleep questionnaires periodically from 6 to 30 weeks of pregnancy. A small subset of these women were also tracked objectively with a device that can track sleeping position.
They then tracked stillbirth, small-for-gestational-age newborns (theorizing that differences in blood flow to the baby could affect growth), and pregnancy related hypertension disorders.
What the researchers found was that the sleep position DID NOT affect these outcomes.
The study is limited in that the stillbirth rate in general is so low that it would take a much larger study to really tease that out… but the data from this set did not show any risk for those who were back sleepers.
While some people were monitored for sleep position, others just filled out a questionnaire. So there could be inaccurate memory of sleep positions and duration in this study.
They also did not track sleeping habits after 30 weeks. However, we can probably presume that the sleep habits from 6-30 weeks continue beyond that point.
My take on this, and what I have been telling my patients for years, is that much of the sleep recommendations are hypothetical and based on no real data. It’s also hard to know what position you are in while sleeping.
So, don’t panic if you fall asleep on your back, or wake up in that position.
I think the data is showing sleep position probably does not affect pregnancy outcomes.