Perinatal morbidity in chronic hypertension.

Objective To investigate if chronic hypertension in the absence of superimposed pre-eclampsia is associated with increased perinatal morbidity (especially small for gestational age babies and preterm deliveries) when compared to the general obstetric population. Design A retrospective cohort study. Setting A tertiary referral obstetric hospital. Participants One hundred and fifty-five pregnant women with chronic hypertension who had a diastolic blood pressure of greater than 90 mmHg before 20 weeks or had pre-existing essential hypertension were studied. The study period was January 1 1991 to June 30 1993. Main outcome measures Perinatal related loss rate, birthweight less than the fifth centile (small for gestational age) preterm delivery, placental abruption and development of superimposed pre-eclampsia. Results Women with chronic hypertension without superimposed pre-eclampsia had an increased rate of small for gestational age babies (10.1%) compared with the general population (4.1%) (odds ratio 2.9 [confidence interval 1.6 to 5.01). Women with chronic hypertension without superimposed pre-eclampsia did not have a significant increase in preterm delivery or perinatal loss. Severe hypertension (diastolic blood pressure ≥ 110) at less than 20 weeks was associated with a trend to an increased risk of small for gestational age babies (odds ratio 3.8 [confidence interval 1.0 to 13.7]), increased rate of delivery at less than 32 weeks (odds ratio 7.4 [confidence interval 1.9 to 29.51) and increased rate of superimposed pre-eclampsia (odds ratio 5.2 [confidence interval 1.5 to 17.21). Women with superimposed pre-eclampsia had the greatest perinatal morbidity. Conclusions Women with chronic hypertension without pre-eclampsia have an increased risk of delivering a small for gestational age baby. Perinatal morbidity and pre-eclampsia is greatest in women with severe hypertension at less than 20 weeks. Preterm delivery is more common in women with superimposed pre-eclampsia.