Relationship between blood pressure level in early pregnancy and subsequent changes in blood pressure during pregnancy.

BACKGROUND: It is not known whether women with high blood pressure in the first trimester are likely to exhibit a large increase in blood pressure during pregnancy.
METHODS: We conducted a retrospective, longitudinal study of 1599 pregnant women, among whom 29 women (1.8%) received antihypertensive medication during pregnancy. The blood pressure levels measured during the first (7.9 +/- 2.4 weeks), second (20.7 +/- 1.2 weeks) and third trimesters (38.4 +/- 1.7 weeks) were analyzed. The obstetric outcomes were examined in five subgroups divided according to the quintile of the first-trimester mean arterial pressure level.
RESULTS: The net change in blood pressure levels (third-trimester value minus first-trimester value) was significantly inversely correlated with the first-trimester blood pressure levels irrespective of the use or lack of use of antihypertensive drugs. Women with the highest quintile first-trimester mean arterial pressure had the largest body weight, exhibited a fall in blood pressure and had the smallest increase in body weight during pregnancy, and were significantly more likely to have a growth-restricted infant.
CONCLUSIONS: Women with high initial blood pressure tended to exhibit a fall in blood pressure, whereas women with low initial blood pressure tended to exhibit a large increase in blood pressure during pregnancy. Women with high initial blood pressure and a small increase in body weight during pregnancy tended to have growth-restricted infants.