Scientists think they've found the cause of morning sickness

Morning sickness is an extremely common side-effect of pregnancy – and one that can become severe and even life-threatening – and now scientists are zooming in on the cause.

A new pre-print study has identified excess levels of a hormone called GDF15 as the main cause of morning sickness.

The researchers believe that the discovery could lead to new treatments for hyperemesis gravidarum, which causes severe nausea and vomiting.

Previous studies have pinpointed the hormone as a cause, but a new study with multiple lines of evidence appears to have confirmed it.

Hyperemesis gravidarum (HG), which affects up to 2% of pregnant women, causes nausea and vomiting so severe that it can lead to starvation, nutrient deficiency and problems with foetal development.

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HG can be passed down in families and most women who experience it in one pregnancy will have a recurrence in additional pregnancies.

HG has long been poorly understood and therefore under-treated, putting women with the condition at an increased risk of pregnancy termination, suicidal ideation and even death.

The researchers write, ‘Our findings support a causal role for foetal derived GDF15 in the nausea and vomiting of human pregnancy, with maternal sensitivity, at least partly determined by pre-pregnancy exposure to GDF15, being a major influence on its severity.

‘They also suggest mechanism-based approaches to the treatment and prevention of hyperemesis gravidarum.’

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The researchers led by Marlena Fejzo, from the University of Southern California Keck School of Medicine, write, ‘Growth Differentiation Factor-15 (GDF15), a hormone known to act on the hindbrain to cause emesis, is highly expressed in the placenta and its levels in maternal blood rise rapidly in pregnancy. Variants in the maternal GDF15 gene are associated with HG.

“Here we report that foetal production of GDF15, and maternal sensitivity to it, both contribute substantially to the risk of HG.

“We found that the great majority of GDF15 in maternal circulation is derived from the feto-placental unit and that higher GDF15 levels in maternal blood are associated with vomiting and are further elevated in patients with HG.’

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