Reproductive hormones and blood pressure during pregnancy

The mechanisms involved in cardiovascular changes during human pregnancy an d the complicated aetiology df gestational hypertension are unclear. Reprod uctive hormones have known effects on the cardiovascular system in the non- pregnant state and in animal systems, but their effects in human pregnancy are uncertain, In this study of pregnant women, the effects of serum concen trations of relaxin, progesterone and oestradiol on arterial blood pressure were studied. Higher serum concentrations of progesterone and relaxin, but not oestradiol, in early pregnancy were related to lower mean systolic blo od pressures in the second and third trimesters. No relationship was found between hormonal concentrations and diastolic blood pressures, However, wom en with a diastolic blood pressure of >90 mmHg in late pregnancy showed sta tistically significant lower relaxin concentrations in early pregnancy in c omparison with women whose diastolic blood pressure was less than or equal to 90 mmHg. In a multivariate analysis, the mean systolic blood pressure (P < 0.0001) and serum relaxin (P < 0.01) in early pregnancy, but not progest erone, were independently related to systolic blood pressure in late pregna ncy, The results support previous experimental and clinical studies. The ef fect of relaxin may be explained by a possible vasodilatatory action seen i n animal studies and appears to be moderate.