LACK OF EVIDENCE FOR A CIRCADIAN-RHYTHM OF IGFBP-1 IN THE MOTHER AND FETUS DURING LABOR

Objective To determine whether the circadian rhythm of circulating lev els of insulin-like growth factor binding protein-1 (IGFBP-1) is evide nt at the time of delivery. Design Prospective observational study in six pregnant women and cross-sectional study in 65 women at the time o f delivery. Subjects Six pregnant women sampled over a period of 24 ho urs, 23 women sampled at the time of elective caesarean section, and 4 2 women sampled at the time of vaginal delivery. Results In the women sampled serially over a 24 hour period there was an obvious circadian rhythm of IGFBP-1 with a peak between 01.00 and 09.00 hours. In the wo men sampled at the time of delivery there was no evidence for any rela tionship between the time of delivery and maternal or fetal levels of IGFBP-1. Conclusions The circadian rhythm of IGFBP-1 is not observed i n women in labour. Therefore, the time of day is not an important conf ounding variable in studies on IGFBP-1 levels at the time of normal de livery.