VARIATIONS IN SERUM RELAXIN (HRLX-2) CONCENTRATIONS DURING HUMAN-PREGNANCY

Study objective. To study variations in serum relaxin concentrations d uring normal and abnormal human pregnancy and parturition and in umbil ical cord blood.Design and patients. Diurnal variations were determine d in samples collected every 2 hours for 24 hours (n=4). Variations du ring pregnancy were studied in samples taken every 4th week from norma l pregnant women (n=26). Additionally samples were collected once a we ek from the 37th week of pregnancy and until spontaneous delivery (n=5 ). Changes in relaxin during early pregnancy (gestational age: 30 to 9 7 days) were studied in serum from 12 normal pregnant women, 13 with s pontaneous abortion and 38 with an ectopic pregnancy. Fetal serum was obtained at delivery from the umbilical vein (n=20). All samples were analysed for relaxin by an ELISA based on human relaxin antibodies. Ma in results. No diurnal variation in relaxin concentrations were found. In normal pregnant women relaxin concentrations increased during the first 14 weeks of pregnancy. From week 14 to 24 a gradual decrease was found and the concentrations remained constant during the last part o f pregnancy. No changes in concentrations were found immediately befor e or during spontaneous delivery. Women with abnormal pregnancies had lower serum relaxin values than normal early pregnant women. The relax in concentration was significantly correlated to the serum HCG concent ration in early pregnancy but not to the serum HPL levels after week 2 8. In the umbilical vein relaxin concentrations were low. Conclusion. The variation in circulating levels of relaxin during human pregnancy differs markedly from those found in other species. This suggests a di fferent role for relaxin in human pregnancy.