Predicting high blood pressure in pregnancy

OBJECTIVE: To identify predictors of pregnancy-induced hypertension and pre-eclampsia in 212 nulliparous women before 20 weeks' gestation and at approximately 28 weeks' gestation. STUDY DESIGN: A randomized, prospective study in a teaching hospital. We performed standardized measurements of systolic and diastolic arterial blood pressures, body mass index, urinary calcium:creatinine ratio and components of the renin-angiotensin system, including platelet angiotensin II binding site density. Attending clinicians were blinded to the results. Outcome was assessed by one observer at the end of pregnancy. Discriminant function analysis was used to identify significant predictors. RESULTS: Fifty-five women had transient, presumed 'white-coat', systolic hypertension at the time of first pregnancy visit; they were twice as likely to develop pregnancy-induced hypertension and pre-eclampsia and five times more likely to deliver prematurely. Body mass index, platelet angiotensin II binding site density and urinary calcium:creatinine ratio measured before 20 weeks gestation were also significant predictors. At 28 weeks of pregnancy, measurements of the blood pressure were significant predictors (reflecting the near clinical expression of the disease), together with the plasma angiotensinogen concentration. CONCLUSIONS: A single systolic blood pressure reading of 140 mmHg or more before 20 weeks' gestation indicates a higher than normal risk of pregnancy-induced hypertension and pre-eclampsia and premature delivery. Discriminator biochemical variables were also identified at this time, which might allow the more rational use of prophylactic measures.