Severe morning sickness linked to complications during pregnancy
Women who have severe morning sickness during the middle or later part of their pregnancy may be slightly more at risk of experiencing complications. But the overall risk, both of severe morning sickness and of complications, is low.
BMJ Group News
What do we know already?
Most women feel or are sick during the first three months of their pregnancy. But some may feel sick for longer. Severe sickness during pregnancy - which is called hyperemesis gravidarum - is caused by high levels of a hormone called human chorionic gonadotrophin (hCG). All women produce hCG during pregnancy but doctors think some women are more sensitive to it than others, and these women have more severe morning sickness.
Studies show that more than 10 in 100 women still have nausea and vomiting after their 20th week of pregnancy.
Some studies have shown a link between severe morning sickness later on during pregnancy and an increased risk of developing health problems such as pre- eclampsia - an illness that some pregnant women can get that usually starts with high blood pressure - and giving birth to a stillborn baby or a baby whose weight is smaller than average.
To find out if severe morning sickness during the later stages of their pregnancy could make women more likely to have complications, researchers looked at 1,155,033 pregnant women. They then looked to see whether women who had been to hospital at least once for severe morning sickness at any time until the 22nd week of their pregnancy were more likely to go on to have complications than women who hadn’t had severe morning sickness.
What does the new study say?
Around 1 in 100 pregnant women had to go to hospital for severe morning sickness during the first 22 weeks of their pregnancy.
Women who had severe morning sickness were more likely to have pre-eclampsia than women who hadn’t had severe morning sickness.
But this didn’t happen very often. Around 8 in 1,000 women who had severe morning sickness had pre-eclampsia, compared to 6 in 1,000 women who didn’t have severe morning sickness.
Women who had severe morning sickness were more likely to have complications involving the placenta during birth than women who didn’t.
But again the number of women this affected was quite small. Around 5 in 1,000 women with severe morning sickness had problems with their placenta, compared with 4 in 1,000 women who didn’t have morning sickness.
Women who had severe morning sickness were also more likely than women who didn’t have severe sickness to have a baby that was smaller than average weight. This affected around 3 in 100 women who had severe morning sickness and 2 in 100 who didn’t.
Women who had severe morning sickness during their second trimester (between the 12th and 22nd week of pregnancy) were more likely to have pre-eclampsia, placenta problems, or a small baby than women who were only affected during their first trimester (before the 12th week of pregnancy).
Experiencing severe vomiting during the later stages of pregnancy did not make women more likely to have a still birth.