Blood pressure changes across gestation in patients with twin pregnancies

Objective: To report blood pressure (BP) across gestation in patients with twin pregnancy. Methods: Historical cohort of all twin pregnancies managed by one maternal-fetal medicine practice from 2005 to 2012. Patients with chronic hypertension were excluded. We reviewed all outpatient BP measurements taken during pregnancy and compared systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) for every 2-week interval starting at 6 weeks. All BP measurements were taken manually in the seated upright position. Results: There were 520 patients with twin pregnancies managed over the study period, 19 (3.7%) were excluded for chronic hypertension, leaving 501 patients for analysis. There were a total of 4985 BP measurements (9.95 per patient) during pregnancy. Starting at 6 weeks' gestation, the SBP, DBP and MAP remained stable until 30 weeks' gestation, when all three began to rise significantly until 38 weeks (p < 0.001). There was no drop in BP in the second trimester. The 95th percentile for systolic BP did not exceed 121 mmHg until 30 weeks and the 95th percentile for diastolic BP did not exceed 80 mmHg until 34 weeks. The 4 - to 10-week postpartum DBP and MAP were significantly higher than the initial DBP and MAP <10 weeks. Conclusions: In patients with twin pregnancies, the BP remains stable from 6 weeks until 30 weeks, at which time it begins to rise steadily. The 95th percentile for SBP and DBP prior to 30 weeks are ∼120 and 80 mmHg, respectively.