A baby's own hormone helps drive morning sickness

Researchers at USC and the University of Cambridge traced the nausea of pregnancy to GDF15, a hormone that acts on the brainstem, and found that most of it in a pregnant woman's blood comes not from her but from the fetus and placenta.

The team measured GDF15 in pregnant women and found that higher levels tracked with worse nausea and, in its extreme form, hyperemesis gravidarum. Women with naturally low GDF15 before pregnancy were at higher risk of severe sickness, while women with beta-thalassemia, a blood condition that keeps GDF15 chronically high, reported almost none.

A mother's own prior exposure to GDF15 appears to set her sensitivity to it, so the same fetal signal can produce very different symptoms in different pregnancies. Experiments in mice supported the desensitization idea. The findings point toward treatments aimed at GDF15 sensitivity itself, though none has yet been tested in pregnant women.

A fetal hormone writes the nausea.