Sleep positions in pregnancy

Linda J. Middlekauff, RN, BSN, LCCE

Sleep positions in pregnancy

Hi Henci!

 

One of my current stdents was told by her physician to sleep "mostly on your left side".  The expectant mom has no phsical problems & has had an uneventful, healthy pregnancy.  She's 32 weeks pregnant.  While I understand that cardiac return is maximized in this position & that relaxin mediates the effects of the increased blood volume in pregnancy, I cannot find any research either supporting or refuting this adivce.

 

Labor is an altogether different matter as this position may be useful when there are complications or when there is fetal distress.

 

I asked this mother if she's able to sleep on her left side, and she said it's very difficult.  I also asked if the physician had said there were any problems in her pregnancy, and she said there were none.

 

To your knowledge, is there any evidence based research on this subject during a healthy pregnancy? 

 

Thank you,

Linda Middlekauff, RN, BSN, LCCE

 

Henci Goer

RE: Sleep positions in pregnancy
(in response to Linda J. Middlekauff, RN, BSN, LCCE)

So I ran a search in PubMed on “sleep position and pregnancy,” and darned if I didn’t turn up a study entitled “Association between maternal sleep practices and risk of late stillbirth: a case-control study.” Now, “stillbirth” is a very scary word, but let’s take a deep breath and look at the study more closely. Investigators interviewed 155 New Zealand women about various aspects of sleep practices that could conceivably be connected to fetal wellbeing who had a late stillbirth (at or after 28 weeks gestation) of a baby free of congenital anomalies. They compared their responses with those of 310 women with ongoing singleton pregnancies matched to the same gestational age. They found that among other factors, women who went to sleep on their left side were less likely to have a late stillbirth compared with women who went to sleep in any other position after taking into account age, ethnicity, high BMI, number of previous children, smoking, and social deprivation. The absolute risk of late stillbirth was 2 per 1000 in women falling asleep on their left side versus 4 per 1000 for women who fell asleep in other positions, or an absolute difference of 2 per 1000.

 

The study, however, had a number of weaknesses:

 

• We know that a difference was found in women who went to sleep on their left side, but who knows if they stayed there? The authors acknowledge that they couldn’t ascertain changes in sleep position during the night. They add that they only found an association with stillbirth in women who neither fell asleep nor woke on their left side, but that still doesn’t mean that women slept all night on their left side, and given how uncomfortable it can get in the the last trimester, it seems unlikely that they did.

• Autopsies were only done in half the cases nor are we told the cause of death when they were done. The theory behind the value of sleeping on the left side is that maternal circulation to the placenta may be diminished in other recumbent positions because of pressure from the weight of the uterus on major blood vessels. Without knowing cause of death, we don’t know whether the demise could be tied to compromised oxygenation.

• “Stillbirth” is defined as deaths occurring during pregnancy or labor. If any of the deaths occurred during labor, sleep position would not have been the cause.

• The investigators don’t adjust for maternal or fetal medical factors such as maternal hypertension or intrauterine growth restriction that could potentially affect fetal vulnerability to compromise in maternal circulation. This means that we don’t know the implications of sleeping position for a healthy woman carrying a healthy fetus.

• Statistical significance is a matter of calculating probabilities. A commentary on this study points out that when numerous comparisons are studied, it is likely that some differences will be found to be statistically significant just by chance. I have seen one strategy to compensate for this, which is to raise the threshold for significance from a p-value of 0.05, meaning there is a 5 out of 100 probability that the finding of a significant difference has occurred by chance, to a value of 0.01, or a 1 out of 100 probability. The investigators used the 0.05 threshold.

 

And let us not forget that finding an association is a long way from demonstrating causation.

 

All that being said, it still would seem that sleeping on the left side might be a good idea except for one catch: getting less than 6 hours sleep a night was also associated with stillbirth. This brings us back to your student. If she is uncomfortable on her left side, it seems to me that it is also important for her to get her rest. How might this dilemma be resolved? Perhaps she might see if she can make herself comfortable enough at least to settle to sleep on her left side. Does she need two pillows under her head so that her shoulder isn’t scrunched? Does she need a pillow between her legs to ease pressure on the underneath leg? How about a cylindrical or rolled one behind her back for support or a thin one underneath her belly? Is the arm on the upper side more comfortable if she hugs a pillow to her chest with it? If none of that works, she can fall back on the need to get the best rest can in the positions she and her unborn baby find the most comfortable.

 

~ Henci

Linda J. Middlekauff, RN, BSN, LCCE

Sleep positions in pregnancy/reply from Linda M
(in response to Henci Goer)
Thank you so much, Henci! This is very interesting yet inconclusive, but I’ll pass this on to my student. Hopefully, this study will encourage other studies to be done on the subject.

Linda

PS I really appreciate your comments about the study with which I totally agree.


From: Henci Goer
Sent: Monday, June 24, 2013 2:03 PM
To: [login to unmask email]
Subject: [Pregnancy_Birth] - RE: Sleep positions in pregnancy

So I ran a search in PubMed on “sleep position and pregnancy,” and darned if I didn’t turn up a study entitled “Association between maternal sleep practices and risk of late stillbirth: a case-control study.” Now, “stillbirth” is a very scary word, but let’s take a deep breath and look at the study more closely. Investigators interviewed 155 New Zealand women about various aspects of sleep practices that could conceivably be connected to fetal wellbeing who had a late stillbirth (at or after 28 weeks gestation) of a baby free of congenital anomalies. They compared their responses with those of 310 women with ongoing singleton pregnancies matched to the same gestational age. They found that among other factors, women who went to sleep on their left side were less likely to have a late stillbirth compared with women who went to sleep in any other position after taking into account age, ethnicity, high BMI, number of previous children, smoking, and social deprivation. The absolute risk of late stillbirth was 2 per 1000 in women falling asleep on their left side versus 4 per 1000 for women who fell asleep in other positions, or an absolute difference of 2 per 1000.



The study, however, had a number of weaknesses:



• We know that a difference was found in women who went to sleep on their left side, but who knows if they stayed there? The authors acknowledge that they couldn’t ascertain changes in sleep position during the night. They add that they only found an association with stillbirth in women who neither fell asleep nor woke on their left side, but that still doesn’t mean that women slept all night on their left side, and given how uncomfortable it can get in the the last trimester, it seems unlikely that they did.

• Autopsies were only done in half the cases nor are we told the cause of death when they were done. The theory behind the value of sleeping on the left side is that maternal circulation to the placenta may be diminished in other recumbent positions because of pressure from the weight of the uterus on major blood vessels. Without knowing cause of death, we don’t know whether the demise could be tied to compromised oxygenation.

• “Stillbirth” is defined as deaths occurring during pregnancy or labor. If any of the deaths occurred during labor, sleep position would not have been the cause.

• The investigators don’t adjust for maternal or fetal medical factors such as maternal hypertension or intrauterine growth restriction that could potentially affect fetal vulnerability to compromise in maternal circulation. This means that we don’t know the implications of sleeping position for a healthy woman carrying a healthy fetus.

• Statistical significance is a matter of calculating probabilities. A commentary on this study points out that when numerous comparisons are studied, it is likely that some differences will be found to be statistically significant just by chance. I have seen one strategy to compensate for this, which is to raise the threshold for significance from a p-value of 0.05, meaning there is a 5 out of 100 probability that the finding of a significant difference has occurred by chance, to a value of 0.01, or a 1 out of 100 probability. The investigators used the 0.05 threshold.



And let us not forget that finding an association is a long way from demonstrating causation.



All that being said, it still would seem that sleeping on the left side might be a good idea except for one catch: getting less than 6 hours sleep a night was also associated with stillbirth. This brings us back to your student. If she is uncomfortable on her left side, it seems to me that it is also important for her to get her rest. How might this dilemma be resolved? Perhaps she might see if she can make herself comfortable enough at least to settle to sleep on her left side. Does she need two pillows under her head so that her shoulder isn’t scrunched? Does she need a pillow between her legs to ease pressure on the underneath leg? How about a cylindrical or rolled one behind her back for support or a thin one underneath her belly? Is the arm on the upper side more comfortable if she hugs a pillow to her chest with it? If none of that works, she can fall back on the need to get the best rest can in the positions she and her unborn baby find the most comfortable.



~ Henci



-----End Original Message-----

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