Preeclampsia in twin pregnancies: incidence and outcome.

OBJECTIVES: To confirm the increased incidence of preeclampsia in twin pregnancy and to determine the relationship to zygosity and placentation; to consider the perinatal outcome of twin pregnancies in this condition.
METHODS: Retrospective study of all twin pregnancies (n = 2473) identified from the Aberdeen Maternity and Neonatal Databank to women resident in the Grampian Region of Scotland for the period 1950-1995.
RESULTS: The increased relative risk for gestational hypertension, preeclampsia, and eclampsia in twin pregnancies compared to singleton pregnancies has been confirmed as significant both in primiparas and multiparas with little variation in rates over the time period under review. Neither the sex of the offspring nor zygosity influences the incidence of hypertensive disease, whereas preeclampsia is more common in association with monochorionic placentation. As the birth weight was lower and placental weight greater in MzMc twins compared to either MzDc or DzDc, there was a higher placental index in such cases. No difference in the birth weights of individual twins, the difference in birth weights between the twins, placental weight, or placental index were found in relation to hypertensive disease. Gestation at delivery was earlier in normotensive twin pregnancies than in those women who developed a hypertensive problem. This leads to a higher perinatal death rate and lower survival rate for the babies in normotensive women with a twin pregnancy.
CONCLUSION: Although gestational hypertension, preeclampsia, and eclampsia all occur more commonly in twin pregnancy, this does not lead to significant growth retardation nor discordant fetal growth and a poor outcome for the twins. Although the incidence of preeclampsia is higher in twin pregnancies with monochorionic placentation, this does not seem to be mediated by deficiencies in placental development as assessed in this study.