In plain words
Supine hypotensive syndrome happens when the growing uterus presses on the big vein and artery that run along the spine. This usually starts after about 20 weeks of pregnancy. Less blood returns to the heart, so blood pressure can fall while lying on the back. Symptoms can include dizziness, nausea, cold sweats, a racing heartbeat, or feeling faint. Most people have no symptoms, because the body adjusts with extra blood vessel routes. Lying on one side often helps those who do feel it. Many providers ask about symptoms when a pregnant person has spent a long time lying on her back. It is not the same as anemia, although both can cause faintness. Feeling faint often is a reason to call a provider.
The deeper version
by the gravid uterus after about 20 weeks reduces venous return and cardiac output by up to about 25 percent in the supine position. Most women compensate through paravertebral and collateral venous circulation, and an estimated 8 to 10 percent become symptomatic. Diagnosis is clinical: a fall in systolic pressure with symptoms on supine positioning, and recovery on lateral tilt. Fetal heart rate changes can accompany maternal hypotension. Its relevance to exercise and sexual positions rests mostly on small studies and expert opinion.
Where it comes up
- Moving your body in pregnancyPregnancy: Your Body
- Sex during pregnancyPregnancy: Your Body
- Blood sugar, dizziness, and energy crashesPregnancy: Eating
What mothers here say about supine hypotensive syndrome
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Sources
- American College of Obstetricians and Gynecologists — Physical Activity and Exercise During Pregnancy and the Postpartum Period, Committee Opinion 804, 2020