Relaxin in human pregnancy serum measured with an homologous radioimmunoassay.

This study reports serum levels of relaxin in normal and special-interest pregnancies using an homologous radioimmunoassay for human relaxin. The mean levels in uncomplicated antenatal patients were lower than those reported in studies using heterologous assays, but the trend in serum levels was similar. Serum levels peaked at ten weeks' gestation and decreased progressively to term. Relaxin was detectable in all pregnant subjects assessed at the time of the first missed menses. The mean relaxin levels in patients having in vitro fertilization and embryo transfer who subsequently delivered a single infant were significantly higher than those in normal antenatal patients at an equivalent gestational age. Patients with twin pregnancies after in vitro fertilization and embryo transfer generally had higher levels than patients with single pregnancies. Some pregnant patients who aborted after in vitro fertilization and embryo transfer had declining levels of relaxin before 40 days postlaparoscopy.

Antenatal uterine activity monitoring of women at increased risk of preterm labour.

The aim of the study was to investigate the usefulness of antenatal uterine activity monitoring in the management of women at increased risk of preterm labour on the basis of a past history of preterm birth or mid-trimester abortion. Uterine activity was recorded every 2 weeks between 20 and 28 weeks gestation. Activity was considered to be increased if pressure changes > 15 mmHg were detected. Fifty-eight women had uterine activity monitoring. Of them, 39 had normal uterine activity. Nineteen women had increased activity and they were randomized to either a study group (9) where the findings were revealed to the clinicians caring for them or a control group (10) where the findings were not revealed. There was no standard regimen of management for the study group except that additional uterine activity monitoring was performed to provide feed back to the clinicians about their interventions. The sensitivity, specificity, positive predictive value and negative predictive value of uterine activity monitoring for preterm births and for preterm births before 32 weeks were disappointing. Uterine activity monitoring was not useful for predicting births prior to 32 weeks; most of these were preceded by prelabour rupture of the membranes. The pregnancy outcome of women with increased uterine activity was not better if clinicians were aware of that increased activity than if they were not.

Antenatal serum levels of relaxin in patients having preterm labour.

This study is the first report of antenatal levels of relaxin measured by homologous radioimmunoassay in peripheral serum from patients who subsequently had a preterm delivery. Serial blood samples were collected antenatally from a group of subjects known to be at increased risk of preterm labour because of a past history of shortened pregnancy. Serum relaxin was measured using an homologous radioimmunoassay based on a synthetic bioactive analogue of the native hormone. In women whose pregnancies ended preterm most measurements were within the range of values previously established in normal antenatal patients although some measurements early in pregnancy were above the normal range. These findings suggest that low serum levels of relaxin are not causatively related to the onset of labour before term.