2ND TRIMESTER AMBULATORY BLOOD-PRESSURE IN NULLIPAROUS PREGNANCY - A USEFUL SCREENING-TEST FOR PREECLAMPSIA

Objective To assess the effectiveness of second trimester 24-hour ambu latory blood pressure measurement as a screening test for pre-eclampsi a. Design Prospective interventional study. Setting John Radcliffe Mat ernity Hospital, Oxford, and Queen Charlotte's and Chelsea Hospital, L ondon. Subjects One hundred and sixty-two normotensive nulliparous wom en recruited at hospital booking clinics. Intervention Ambulatory bloo d pressure was measured at 18 and 28 weeks gestation using the TM2420 monitor. Main outcome measure The development of pre-eclampsia. Result s Awake systolic and mean arterial pressures were significantly increa sed (P<0.02) at 18 weeks in those who later developed pre-eclampsia. T hose differences were more apparent at 28 weeks at which time the dias tolic pressure was also increased (P<0.01). At both stages of gestatio n the higher readings were sustained during sleep so that the awake-sl eep differences were similar in relation to each outcome. The group wi th incipient pre-eclampsia had a significantly faster heart rate at bo th 18 and 28 weeks (P< 0.002) The sensitivity in predicting pre-eclamp sia for a mean arterial pressure of 85 mmHg or greater at 28 weeks was 65%, with a positive predictive value of 31%. The sensitivity and pos itive predictive value for a test combining a mean arterial pressure o f 85 mmHg or greater and a heart rate of 90 bpm or greater were 53% an d 45%, respectively. Conclusion Although second trimester ambulatory b lood pressure is significantly increased in women who later develop pr e-eclampsia, the predictive values for blood pressure alone are low. T he efficiency of the test is increased by combining the awake ambulato ry heart rate and blood pressure measurement together. If an effective method for preventing, pre-eclampsia becomes available (commencing at 28 weeks gestation), then awake ambulatory blood pressure and heart r ate may have some clinical value as a screening test.