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 (10.9%) compared with the general population (4.1%) (odds ratio 2.9 -confidence interval 1.6 to 5.0). 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 > or =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 29.5-) and increased rate of superimposed pre-eclampsia (odds ratio 5.2 -confidence interval 1.5 to 17.2-). 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.