Serum relaxin and steroid hormones in spontaneous abortions.

To assess the capacity of the corpus luteum to secrete steroid hormones and relaxin during spontaneous abortion, human chorionic gonadotropin (hCG), progesterone, 17 alpha-hydroxyprogesterone (17-OHP) and relaxin concentrations were determined in serum samples obtained from 16 spontaneously aborting first-trimester patients and 5 asymptomatic, apparently normal women who subsequently aborted. hCG and P were subnormal in more than half of aborting patients, and 17-OHP in half of them. However, relaxin was normal in most of them. No patient with subnormal relaxin levels had hCG values in the normal range. Such a relationship was not found between hCG and 17-OHP values. Hence, decreases in placental activity seem to precede a decrease in luteal ability to secrete relaxin but not to secrete steroid hormones. Some aborting patients with subnormal 17-OHP levels had normal relaxin values. All but 1 woman who aborted subsequently had subnormal 17-OHP values at a time when relaxin levels were normal. Therefore, in some aborting patients, the ability of the corpus luteum to secrete steroid hormones is impaired at a time when its capacity to secrete relaxin is preserved.