Preeclampsia in twin pregnancy--severity and pathogenesis.

The incidence of preeclampsia in a consecutive series of 642 twin pregnancies was 25.9% compared with 9.7% in singleton pregnancies (p less than 0.001); in primiparas it was 35.2% and in multiparas 20.4% (p less than 0.001). Preeclampsia in twin pregnancies was more commonly of early onset (p less than 0.001) and the maternal disease more severe as assessed by the incidences of severe hypertension (p less than 0.001), proteinuria (p less than 0.004), and eclampsia (p less than 0.01). There were 1 maternal and 12 perinatal deaths. Oestriol excretion before the emergence of preeclampsia was lower in patients with severe compared with milder preeclampsia (p less than 0.05) as was plasma glucose concentration (p less than 0.05). Mean birth and placental weights according to gestation, tended to be lower in the severe group compared with uncomplicated cases and those with milder preeclampsia, as were also the placental-fetal weight ratios. The similarity of results with those already reported for singleton pregnancy suggested a similar pathogenesis for preeclampsia in twin and singleton pregnancies.