Sleeping on Your Back Is Dangerous Starting at 16 Weeks of Pregnancy

I have three pregnancy books that I’d saved from my pregnancy with my son, now age 4 ¾:  What to Expect When You’re Expecting (Hiedi Murkoff, Arlene Eisenberg and Sandee Hathaway, B.S.N, Workman Publishing, 2002), of course; Your Pregnancy Week by Week (Dr. Glade B. Curtis, M.P.H., OB.GYN and Judith Schuler, M.S., Da Capo Publishing, 2004); and my favorite, From Conception to Birth: A Life Unfolds, an incredible book featuring photos that show a baby’s development from conception to birth (Alexander Tsiaras, Doubleday, 2002).  For this pregnancy, my high-risk pregnancy practice handed me You & Your Baby: Pregnancy (Dr. Laura Riley, OB/GYN, Meredith Books, 2006).  Having already survived my son’s pregnancy and birth, I’ve been mellow during this pregnancy with my reading.  Until last week…

I still read each and every book, but often get to the appropriate chapter(s) a week or so after I’ve hit the milestone.  Until last week, my slacker system was working out just fine.   That is, until Your Pregnancy Week by Week, in its “Week 16” chapter, which I read in my 17th week, stated:

Don’t Lie on Your Back

Week 16 is the turning point—no more lying flat on your back in bed while resting or sleeping or lying flat on the floor while exercising or relaxing.  This position puts extra pressure on the aorta and vena cava, which can reduce blood flow to your baby.

Blood flow from mother to growing baby supplies the nutrients the fetus needs to develop and to grow.  Don’t endanger your baby’s health and well-being by forgetting this important action.

Reclining in a chair or propped up with pillows is OK.  Just don’t lie on your back!

This dire warning conflicts with what I’d already read in the “Week 14” chapter of You & Your Baby: Pregnancy, which is as follows:

Getting comfortable at night

Some of that advice overload you’ve been getting has probably included cautionary tales about never sleeping on your stomach or back for fear of injuring your baby.  The truth is this: If a certain sleep position is bad for your baby or you, it will be so uncomfortable that your body will naturally shift.

Where do these cautions come from?  Never sleeping on your stomach makes a certain amount of sense—after all, there’s a baby between you and your bed, and sleeping on your stomach may make you feel like you’ve rolled over onto a football.  That position in probably more uncomfortable for you than it is for your baby, however, and the uterus is designed to protect your baby from harm.

As for never sleeping on your back, that rule stems from the fact that you have major blood vessels that lie to the right of your spine.  Sleeping on your back causes the weight of the uterus to press down on them and decrease blood circulation.  When you compress one of these veins, known as the vena cava, less blood flow is returned to your heart.  That can make your blood pressure drop enough to make you feel sweaty, dizzy or even nauseous.  Your body naturally protects you in this situation:  By the time your uterus is heavy enough to compress the vein, you’ll be so uncomfortable lying on your back that your body will flip over, even if you’re asleep.  So go ahead and sleep any way you like. …

You & Your Baby: Pregnancy had comforted me, convincing me that my body would respond appropriately to my and my son’s needs during this pregnancy.  But, when in my 17th week, I read that lying on my back was “endangering my baby’s health and well-being,” I was devastated because I hadn’t been uncomfortable sleeping or lying on my back, so I’d continued to do so.  And, now that I have this warning, of course I would never knowingly lie on my back, but I move into this position while I sleep because it’s not uncomfortable.  I just woke up from an afternoon nap—flat on my back.

My only other pregnancy advice book is What to Expect When You’re Expecting, so I’ve of course looked through it.  The book doesn’t address sleep position until its “The Fifth Month:  Approximately 18 to 22 Weeks” chapter, and I just hit 18 weeks of pregnancy last Friday.  It states:


“I’ve always slept on my stomach.  Now I’m afraid to.  And I just can’t seem to get comfortable any other way.”

Giving up your favorite sleep position during pregnancy can be as traumatic as giving up your teddy bear as when you were six.  You’re bound to lose some sleep over it—but only until you get used to the new position.  And the time to get used to it now, before your expanding belly makes it even more difficult to get comfortable. 

Two common favorite sleep positions—on the belly and on the back—are not the best choices during pregnancy.  The belly position for obvious reasons:  as your stomach grows, it’s like sleeping on a watermelon.  The back position, though more comfortable, rests the entire weight of your pregnant uterus on your back, your intestines, and two major blood vessels:  the aorta (the vein responsible for returning blood from the heart to the rest of your body) and the vena cava (the vein responsible for returning blood from the lower body to the heart).  This can aggravate backaches and hemorrhoids, make digestion less efficient, interfere with breathing and circulation, and possible cause hypotension or low blood pressure.

This doesn’t mean you have to sleep standing up.  Curling up or stretching out on your side—preferably the left side—with one leg crossed over the other and with a pillow between them, is the best for both you and your fetus.  It not only allows maximum flow of blood and nutrients to the placenta but also enhances efficient kidney function, which means better elimination of waste products and fluids and less swelling (edema) of ankles, feet and hands.

Very few people, however, manage to stay in one position through the night.  Don’t worry if you wake up and find yourself on your back or abdomen.  No harm done; just turn back to your side. …

Every night, I start out on my side, with a pillow between my legs, exactly as I’m supposed to.  But, every night, when I wake up to use the bathroom, have insomnia, or awake in the morning, I inevitably find myself on my back at least once.  My three books are giving me conflicting information, from “no harm done” to “you’ll change sleep positions when your body tells you to” to “you’re endangering your baby.”

I’m not a mellow person.  I’m anxiety-prone.  So, I’m frightened that, unconsciously in my sleep, my body is failing me, for it’s not uncomfortable sleeping on its back, as it should be; therefore, I’m putting my baby at risk, based on one out of three books.

The rational me—who recognizes that the book that provides the least information about sleep positions gave the strongest, scariest warning—is going to ask her doctor for advice at tomorrow’s appointment.

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