THE CONCENTRATION OF RELAXIN IN THE BLOOD SERUM AND OTHER TISSUES OF WOMEN DURING PREGNANCY*

Abstract

INVESTIGATIONS on the physiology of relaxin would indicate that it is a hormone of pregnancy (1, 2). Additional evidence for this concept may be obtained also from studies on the presence of this hormone in the blood and other tissues during gestation. The concentration of relaxin in the blood of the rabbit (3) and the guinea pig (4) and in the ovary of the pregnant sow increases progressively during pregnancy until a plateau is reached, and then drops precipitously at parturition. In the human being, however, relaxin has been detected in the first part of pregnancy but not in the last trimester (5, 6). Pommerenke (6) reported a drop in the level of serum relaxin of women in the fifth month of pregnancy and a total absence (at 5–6 ml. of serum) by the eighth month. The present investigation was undertaken to determine quantitatively the blood serum levels of relaxin in women throughout pregnancy and at parturition. In addition, several pregnancies complicated by pre-eclampsia and diabetes were studied.