Association between severe nausea and vomiting in pregnancy and lower rate of preterm births.

Nausea and vomiting in pregnancy has been associated with some reduction in miscarriage in other studies. However the relationship between nausea and vomiting during pregnancy and preterm birth/low birthweight in newborns is inconsistent; therefore the objective of the study was to clarify this possible association. The population-based large control (without any defects) data set of the Hungarian Case-Control Surveillance System of Congenital Abnormalities was evaluated. Of 38,151 controls, 3869 (10.1%) had medically recorded and treated nausea and vomiting during pregnancy. The proportion of mothers who later delivered girls was higher in this group. Mothers with nausea and vomiting in pregnancy had a somewhat (0.3 week) longer gestational age and a lower proportion of preterm births (6.4% vs. 9.5%). This finding may be connected with the favourable hormonal milieu (larger placenta, higher level of chorionic gonadotrophin and oestrogens) of pregnant women with nausea and vomiting.