Objective: To determine the proportion of births complicated by either a pre-existing or a gestational non-proteinuric hypertension, presenting at <34 weeks' gestation, and the associated incidence with 1 or more serious perinatal complications or birth weight <3rd centile for gestational age.
Methods: A retrospective chart review was conducted in 5 international centres, from 1998 to 2002, where "tight" control (normalization) of blood pressure (BP) is the norm. International Classification of Diseases (ICD) codes were used to identify women who delivered at > or =20 weeks' gestation, with any hypertensive disorder of pregnancy. Women were included if they had a diastolic blood pressure (dBP) of 90 to 109 mm Hg, due to either a pre-existing or a gestational non-proteinuric hypertension, presenting at <34 weeks' gestation. Women were excluded if they had ongoing severe hypertension, or if at presentation with dBP of 90 to 109 mm Hg, they had 1 or more of the following: proteinuria, an indication for "tight" control of BP or imminent delivery, or a known intrauterine fetal death or lethal fetal anomaly. Data were collected on paper forms, scanned into an electronic database, and summarized descriptively by type of hypertension.
Results: There were 305 eligible women (0.7% deliveries, 12.8% hypertensive deliveries) identified with non-proteinuric hypertension that was either pre-existing (133 [43.6%]) or gestational (172 [56.4%]). Regardless of hypertension type, 16.4% (n = 50) of pregnancies were complicated by birth weight <3rd centile or 1 or more serious perinatal complications, 34.3% (n = 100) by preterm birth, 30.8% (n = 94) by preeclampsia, and 2.0% (n = 6) by serious maternal complications.
Conclusion: Non-proteinuric pre-existing or gestational hypertension, presenting before 34 weeks' gestation, identifies a subpopulation of hypertensive pregnant women at both substantial perinatal risk and maternal risk. The CHIPS (Control of Hypertension In Pregnancy Study) trial is designed to determine how best to manage the hypertension of such women in order to optimize perinatal outcome.