Hyperemesis gravidarum during second trimester linked to placental complications

Women whose pregnancies are complicated by hyperemesis gravidarum in the second trimester are at a much higher risk of placental dysfunction disorders such as placental abruption and small-for-gestational age (SGA) babies, according to a study appearing in the January 30, 2013, issue of BJOG: An International Journal of Obstetrics and Gynaecology.

The population-based cohort study-which evaluated 1,156,050 pregnancies in the Swedish Medical Birth Register between 1997 and 2009-found that women with hyperemesis gravidarum in the first trimester had only a slightly increased risk of preeclampsia.

Women with hyperemesis gravidarum with first admission to a hospital in the second trimester had a more than doubled risk of preterm (<37 weeks) preeclampsia, a threefold increased risk of placental abruption, and a 39% increased risk of a SGA newborn. Adjusted odds ratios [95% confidence intervals] were: 2.09 [1.38–3.16], 3.07 [1.88–5.00] and 1.39 [1.06–1.83], respectively.

The researchers note that their findings suggest that hyperemesis gravidarum could be associated with abnormal placentation. “As hCG levels may be both a cause and an effect of placentation, the time of onset of hyperemesis gravidarum may influence the risks of abnormal placentation disorders,” they write. “In very early pregnancy, high hCG levels may favour normal pregnancy development, whereas, later in pregnancy, abnormal placentation may cause high hCG levels.”

To the researchers’ knowledge, no previous study has investigated hyperemesis gravidarum occurring in the first and second trimesters separately when studying associations with adverse pregnancy outcomes.

Bolin M, Åkerud H, Cnattingius S, Stephansson O, Wikström A. Hyperemesis gravidarum and risks of placental dysfunction disorders: a population-based cohort study. BJOG. 2013. Epub ahead of print.