There is extensive evidence that prepregnancy chronic hypertension is associated with a high risk of development of severe hypertension and preeclampsia and birth of small-for-gestational-age neonates. However, previous studies have not reported whether antihypertensive use, blood pressure control, or normalization of blood pressure during early pregnancy influences the rates of these pregnancy complications.

The purpose of this study was to stratify women with prepregnancy chronic hypertension according to the use of antihypertensive medications and level of blood pressure control at the first hospital visit during the first trimester of pregnancy and to examine the rates of severe hypertension, preeclampsia, and birth of small-for-gestational-age neonates according to such stratification.

We conducted a prospective study of 586 women with prepregnancy chronic hypertension, in the absence of renal or liver disease, that was booked at a dedicated clinic for the management of hypertension in pregnancy. The patients had singleton pregnancies and were subdivided according to findings in their first visit: group 1 (n=199), blood pressure <140/90 mm Hg without antihypertensive medication; group 2 (n=220), blood pressure <140/90 mm Hg with antihypertensive medication; and group 3 (n=167), systolic blood pressure ≥140 mm Hg and/or diastolic blood pressure ≥90 mm Hg, despite antihypertensive medication. In the subsequent management of these pregnancies, our policy was to maintain the blood pressure at 130–140/80–90 mm Hg with the use of antihypertensive medication; antihypertensive drugs were stopped if the blood pressure was persistently <130/80 mm Hg. The outcome measures were severe hypertension (systolic blood pressure ≥160 mm Hg and/or diastolic blood pressure ≥110 mm Hg), preterm and term preeclampsia (in addition to hypertension at least 1 of renal involvement, liver impairment, neurologic complications, or thrombocytopenia), and birth of small-for-gestational-age neonates (birthweight <5th percentile for gestational age). The incidence of these complications was compared in the 3 strata.

The median gestational age at presentation was 10.0 weeks (interquartile range, 9.1–11.0 weeks). In groups 2 and 3, compared with group 1, there was a significantly higher body mass index, incidence of black racial origin, and history of preeclampsia in a previous pregnancy. There was a significant increase from group 1 to group 3 in the incidence of severe hypertension (10.6%, 22.2%, and 52.1%), preterm preeclampsia with onset at <37 weeks of gestation (7.0%, 15.9%, and 20.4%), and small for gestational age (13.1%, 17.7%, and 21.1%), but not term preeclampsia with onset at ≥37 weeks of gestation (9.5%, 9.1%, and 6.6%).

In women with prepregnancy chronic hypertension, the rates of development of severe hypertension, preterm preeclampsia, and small for gestational age are related to the use of antihypertensive medications and the level of blood pressure control at the first hospital visit during the first trimester of pregnancy.