What causes ‘extreme morning sickness’? What we know, don’t know and suspect about hyperemesis gravidarum |
Most women experience some nausea and vomiting in early pregnancy.
Although this is called morning sickness, it can happen at any time of day. Up to 80% of women report nausea and vomiting throughout the day.
While morning sickness is unpleasant and can be incapacitating, milder forms are usually manageable and often get better after the first three months of pregnancy.
But around one in 50 pregnant women (1–3% worldwide) experience morning sickness so extreme they are unable to eat or drink normally or do everyday activities.
This condition, called hyperemesis gravidarum, can last the whole pregnancy and be dangerous for both the woman and the fetus. It is the most common cause of hospitalisation in early pregnancy, but research is still emerging about exactly why it happens.
Here’s what we know, don’t know and suspect.
Until about five years ago, scientists believed the pregnancy hormone, human chorionic gonadotropin (hCG), was the culprit. But we now know the main cause of all morning sickness – including hyperemesis gravidarum – is high levels of a hormone called GDF15.
A person’s sensitivity to GDF15 depends on how much of this hormone their bodies produce before pregnancy.
Women with naturally low pre-pregnancy levels are more sensitive to the GDF15 the placenta........