Arterial blood pressure--the pattern of change in twin pregnancies.

An epidemiological study of all primigravid twin pregnancies delivered in Aberdeen between 1950 and 1969 was performed to determine the pattern of arterial blood pressure changes. There is a greater fall from non-pregnant levels in diastolic blood pressure by mid pregnancy and a greater rise of diastolic pressure by delivery. These changes are independent of age, body size and rate of weight gain during pregnancy. The expected increased incidence of proteinuric pre-eclampsia is also independent of rate of weight gain when defined for twin pregnancies.