Sex ratio and twinning in women with hyperemesis or pre-eclampsia

We examined twinning and fetal gender in births of women with a hospital diagnosis of pre-eclampsia or hyperemesis. We also investigated sex ratio in infants whose mothers had had hyperemesis or pre-eclampsia in a different pregnancy. From all the hospitalized cases in Denmark between 1980 and 1996 we extracted 6,227 births with hyperemesis and 24,764 with preeclampsia. Twins were more frequent in pregnancies with either condition. The male to female sex ratio was 1.04 (95% CI = 1.02-1.05) in the reference population, 0.87 (95% CI = 0.82-0.91) in births with hyperemesis, and 1.10 (95% CI = 1.07-1.12) in births with pre-eclampsia. Women with pre-eclampsia had slightly more males also in non-affected pregnancies.