Changes in blood pressure during healthy pregnancy: a longitudinal cohort study.

Objective: To study longitudinally changes in blood pressure (BP) and heart rate (HR) during healthy pregnancies and to evaluate the influence of parity, pregestational overweight, and excessive weight gain.

Methods: A prospective longitudinal cohort study of 57 healthy white women with singleton pregnancies. BP and HR were measured repeatedly at gestational age 14-16 weeks, 22-24 weeks, 30-32 weeks, 36 weeks, and 6 months postpartum using both an oscillometric measurement device (Dinamap) and finger arterial pressure (Finometer PRO).

Results: SBP, DBP, and mean arterial pressure (MAP) reached a statistically significant trough at gestational age 22-24 weeks using both measurement devices. When compared with the nonpregnant measurement, SBP at gestational age 22-24 weeks was 6.2 mmHg [95% confidence interval (95% CI) 1.3-11.2] lower measured by Finometer and 7.2 mmHg (95% CI 4.2-10.1) lower measured by Dinamap. DBP and MAP were 8.9 mmHg (95% CI 4.6-13.2) and 9.8 mmHg (95% CI 5.3-14.2) lower measured by Finometer. Measured by Dinamap, DBP and MAP were 4.5 mmHg (95% CI 1.7-7.3) and 5.4 mmHg (95% CI 2.8-7.9) lower at gestational age 22-24 weeks when compared with the nonpregnant state. SBP was significantly higher in women with pregestational BMI at least 25 kg/m with both measurement devices (both P < 0.05). There were no differences in SBP, DBP, or MAP depending on parity or excessive weight gain.

Conclusion: BP measured repeatedly by two different noninvasive devices during pregnancy and postpartum showed a statistically significant drop in mid-pregnancy, followed by a progressive increase until term.