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Does Sleeping on Your Back Increase Stillbirth Risk?
Dr. Jones: Finding a comfortable position in bed when you're pregnant can be hard. There's just so much of you. But can some sleeping positions be harmful to you and your baby?
A recent British study suggested that women who sleep on their backs in their third trimester of pregnancy are at increased risk of stillbirth. This shouldn't be complicated, but it is.
And here in the studio to help us understand the strengths and weaknesses of this study are not one, but three specialists in high-risk pregnancy from the University of Utah, Dr. Martha Monson, Dr. Lauren Theilen, and Dr. Karen Gibbins are here in the studio. Thanks for coming, all three of you. Does that mean you disagree?
Dr. Monson: No, actually.
Dr. Theilen: No. Absolutely not.
Dr. Gibbins: This is a rare circumstance.
Stillbirth Causes and Frequency
Dr. Jones: Well, this is good news. So you all agree that there are some problems here about either sleeping on your back or this study. So, let's talk a little bit about that. I actually understand that the entire division, some 15 specialists in high-risk obstetrics, have said, "Wait a minute, there's a problem with this study." Let's talk about it. What is stillbirth?
Dr. Theilen: This is Lauren Theilen, and we define stillbirth as the death of a fetus within the womb that happens at or after 20 weeks of pregnancy.
Dr. Jones: Okay. And how often does it happen?
Dr. Gibbins: In the United States, we currently estimate that stillbirth happens in about 1 of every 160 pregnancies. So that comes out to about 26,000 stillbirths in a year.
Dr. Jones: Well, then, what are the causes? I mean, are they all the same cause, or what's going on here?
Dr. Monson: This is Martha Monson here, and there are multiple causes. We can go over that. So problems such as preterm labor and multiple gestations, so this would be like twins or a triplet pregnancy, and placental abruption, so that's when the placenta starts to separate from the uterus prematurely, are thought to cause about one in three stillbirths, especially those that occur before 24 weeks.
Other causes such as placental insufficiency‚ when there's placental failure that leads to poor baby growth, is thought to be the cause in about one in four stillbirths, especially those that occur after 24 weeks. Of course, there are birth defects or genetic syndromes, and these are thought to cause about 1 in 10 stillbirths. Infections of the baby, the placenta, or the mother are thought to cause about 1 in 10 stillbirths.
Dr. Jones: So that means about . . . for the unexplained, because if we're talking about the position you're in, it may be in the unexplained group, that's maybe one in four, one, about a quarter?
Dr. Monson: Yeah, about that, about a quarter of stillbirths.
Dr. Gibbins: One in four or fewer.
Examining the Study’s Methodology and Limitations
Dr. Jones: Or fewer. Okay, so well, then . . . what's the problem, if any, if pregnant women sleeping on their backs, how many people are we talking about who are sleeping on their backs, and how did they get this number?
Dr. Gibbins: So that's one of the problems with the way the study was conducted. The best way to find out what is happening during a pregnancy is to collect it when it is happening. However, that's very difficult. So, stillbirth is a very rare occurrence, thankfully. The way that these researchers collected this data is they asked women to recall how they were sleeping during their pregnancies. Sometimes, they asked women to recall this multiple weeks after the stillbirth and the delivery had occurred. So that would be like asking you a month and a half ago, "How did you go to bed that night?"
And so at this point and time, women who've experienced stillbirth: A) They've forgotten. B) They've been searching the internet and any resource they can find for why this horrible thing happened to them, and they may have seen that some people have a suspicion that sleeping on your back may have caused their stillbirth. Because of being exposed to those ideas out there, they're more likely to report when a researcher asks them, "You know what? I bet I did sleep on my back. I am blaming myself, I'm feeling guilty, I'm wishing I had done something differently, and so I'm going to say I slept on my back."
How Many Pregnancies Are Affected?
Dr. Jones: So it's the way the study is conducted and maybe the way the questions are answered that might affect this statistic of this twice the increased risk. But even if the chance is 1 in 1000 of people who might have been on their back, that's still a tiny number.
Dr. Gibbins: It is still a very tiny number. And when we're talking about making a broad recommendation for all pregnant women, and we're talking about more than 4 million women a year in this country. And just like you are saying, if we're talking about a small percentage of the 26,000 stillbirths in this country, you get down to a few thousand overall that could even be affected by this.
Dr. Jones: Well, I would have to say, if you'd ask me now, now if this was 100 years ago when I was pregnant, I couldn't have told you where I was sleeping. And in the third trimester, you're all over the bed as best your big belly can do. When I made noises, I'm not using the word snoring because it's so unladylike, but if I did make noises when I was pregnant, my husband, who's the sleep doctor, would nudge me, and then I'd roll into another position. So you're all kind of over the bed. In any given night I might have spent . . . I don't know. So women have heard about the back-to-sleep business and with their babies . . .
Dr. Gibbins: Correct.
Dr. Jones: . . . and they might be sensitized to their own sleep.
The Influence of the ‘Back to Sleep’ Campaign on Pregnant Women
Dr. Monson: And I think that's . . . The Back to Sleep campaign, you know, what Dr. Jones is referring to is the idea that sudden infant death syndrome could be prevented by putting your newborn on their back when they're sleeping as opposed to putting them on their side or their front. And that has been a public health measure with great success. It is very clear that putting your baby to sleep on their back is the right thing to do and will prevent suffocation deaths for these babies. And I think that is exactly why this concept is so appealing. If we had something . . .
Dr. Theilen: Modifiable.
Dr. Monson: . . . modifiable, as "simple" as that sort of behavioral change, that would be wonderful.
Dr. Jones: Right.
Dr. Monson: However, I think it's a reach in this situation.
The Future of Sleep and Pregnancy Research
Dr. Jones: I want to talk a little bit about the biological plausibility. Meaning, somebody did this big study because somebody thought there might be some biology. And we know that women in their third trimester tend to snore or make noises. And snoring might lead to obstructive sleep apnea, meaning they're not getting as much oxygen to the baby or themselves. Or, you know, they're sleeping on their big blood supply. So, there is little biological plausibility.
Dr. Theilen: Yeah, absolutely.
Dr. Jones: So we need a study that will actually do a better job. Are we doing that study?
Dr. Gibbins: So yes and no. There is a large multicenter trial that has been completed in the United States, looking at approximately 10,000 women during their first pregnancies. In that study, a subset of those women had very intensive sleep assessments during their pregnancy. And that data has not been fully analyzed and released yet. I'm hopeful that that will shed some light on this issue. Because that data was collected during the pregnancy when women didn't know what outcome they were going to have. So, it's more likely to be accurate and predictive.
The Key Takeaway for Expecting Mothers and Their Partners
Dr. Jones: Right. Well, and I'm going to give a shout-out to our very own department, which helped really lead this sleep assessment with these many, many women. So what's the takeaway for our listeners, pregnant or not pregnant, and bed partners of pregnant women? What should we be telling them?
Dr. Gibbins: I want women to not feel guilty. That's my biggest takeaway. We do not have enough data to say that sleeping on your back leads to stillbirth. At best, I think it may be linked to sleep apnea. And then the sleep apnea, exactly like you were saying, is the cause, not the sleeping on your back. It is hard enough to get pregnant and to sleep well. The stress caused by trying to sleep in a position that is unnatural to you is more likely detrimental in my mind than the act of sleeping on your back.
Dr. Jones: And we all, we've talked about stress in pregnancy and how that's not good for your baby.
Dr. Gibbins: That's not good for your baby.
Dr. Jones: So get a good night's sleep and grow your baby as best you can. Good luck, and thank you for joining us on The Scope.
updated: March 14, 2025
originally published: March 8, 2018
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