Women who suffer severe morning sickness in the second trimester of pregnancy may have an increased risk of experiencing complications, such as pre-eclampsia, a new study suggests.

One of the most common symptoms of pregnancy is morning sickness, which involves feelings of nausea and/or vomiting at any time of the day. However, hyperemesis gravidarum (HG) is an extreme form of this. It involves persistent nausea and vomiting, which is so severe, it can cause dehydration, malnutrition and weight loss.

It occurs in up to 3% of pregnancies and is the most common cause of hospitalisation in early pregnancy.

Swedish scientists analysed the Swedish medical birth register between 1997 and 2009. This included details on women who had been hospitalised for HG and those who had not.

The scientists focused on three complications - pre-eclampsia (dangerously high blood pressure in the mother), placental abruption (premature separation of the placenta) and babies who are considered small for their gestational age (SGA).

The study found that women with HG in their first trimester had a slightly increased risk of pre-eclampsia, but no increased risk of SGA or placental abruption.

However this changed if the HG continued into the second trimester. Compared to pregnant women without the condition, those with HG in their second trimester had twice the risk of developing pre-eclampsia, were three times more likely to suffer placental abruption and had an increased risk of having an SGA baby.

"The results indicate that pregnancies with HG in the second trimester demand an increased alertness and supervision during the pregnancy for development of any adverse outcomes.

"Further research is needed to consider the best treatment and techniques for surveying blood pressure and foetal growth in these high risk women," the team from Uppsala University said.

Details of these findings are published in BJOG: An International Journal of Obstetrics and Gynaecology.

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