HYPERTENSIVE AND NORMAL-PREGNANCY - A LONGITUDINAL-STUDY OF BLOOD-PRESSURE, DISTENSIBILITY OF DORSAL HAND VEINS AND THE RATIO OF THE STABLEMETABOLITES OF THROMBOXANE A(2) AND PROSTACYCLIN IN PLASMA

Objective By combining serial measurements of the circulating concentr ations of thromboxane A, and prostacyclin with measurements of venous distensibility (taken during the pregnancies of both normal women and those with pregnancy induced hypertension or pre-eclampsia), to test t he following hypotheses: 1. that changes in the venous plasma ratio of thromboxane (TXB(2)) and 6-keto-PGF1 alpha would correlate with chang es in the blood pressure of women developing and recovering from pregn ancy induced hypertension or pre-eclampsia and 2. that changes in veno us distensibility would correlate with changes in arterial blood press ure in pregnancy induced hypertension or pre-eclampsia. Design Prospec tive, longitudinal cohort study. Setting John Hunter Hospital clinic, Newcastle, Australia. Subjects One hundred and sixty primiparous women , recruited when presenting for their first routine antenatal visit, w ere investigated at, or close to, 19, 28 and 37 weeks of gestation; a subgroup was also studied in the postnatal period. The measurements of the patients who developed pregnancy induced hypertension or pre-ecla mpsia were compared with those of controls selected from the cohort. M ain outcome measures Serial measurements of the circulating concentrat ions of the stable metabolites of thromboxane A, and prostacyclin (TXB (2) and 6-keto-PGF1 alpha, respectively), venous distensibility and im mediate (no rest) and resting (for at feast 30 min) blood pressures. R esults There was no significant difference between the subject and con trol groups at any time during or after the pregnancy in the concentra tions of prostaglandin metabolites, their ratio or venous distensibili ty. In contrast, there was a significant difference between the groups at 19 weeks for immediate and resting readings of diastolic pressure (6 mmHg (95% CI 1.5 to 10.5) and 4 mmHg (95% CI 0.1 to 7.9), respectiv ely). These differences increased through the pregnancy but mean postn atal readings for the groups were almost identical suggesting that the subjects were not intrinsically hypertensive compared with controls. Blood pressures for the subject group, both immediate and resting, wer e significantly different from the 19 week readings at 28 weeks (diast olic) and at 37 weeks (systolic and diastolic). The only significant c hange from first readings among controls was in postnatal systolic pre ssure which was significantly higher than 19 week values, probably ref lecting the vasodilatation, with accompanying hypotension, of early, n ormal pregnancy, This difference was not observed in those who subsequ ently developed pregnancy induced hypertension or pre-eclampsia. Concl usions Our study was unable to demonstrate differences in circulating metabolites or venous distensibility between normotensive women and th ose with pregnancy induced hypertension or pre-eclampsia. If pregnancy induced hypertension or pre-eclampsia in humans represents not so muc h the presence of abnormal constrictor influences as a process initiat ed by failure of normal vasodilatation in early pregnancy, studies car ried out later may detect mainly adaptive and secondary changes.