Hormonal influence on the uterine contractility during ovarian stimulation

High-frequency uterine contractions (UC) at the time of embryo transfer hav e been shown to hamper the outcome of in-vitro fertilization (IVF). As UC a re postulated to be hormone-regulated, we aimed to investigate the role of plasma oestradiol and progesterone concentrations on UC during ovarian stim ulation for IVF, A total of 59 women were studied on the day of administrat ion of human chorionic gonadotrophin (I-ICG) and embryo transfer. Plasma oe stradiol and progesterone concentrations were measured, and 5 min ultrasoun d scans of the uterus were digitized with an image analysis system to asses s UC frequency and direction, Cycles were sorted according to whether proge sterone concentrations on the day of embryo transfer were less than or equa l to 100 (rt = 34) or >100 (n = 25) ng/ml, On the day of HCG, UC frequency was similar in both groups at 4.5 +/- 0.2 and 4.6 +/- 0.3 UC/min (mean +/- SE) respectively. On the day of embryo transfer, UC frequency remained stea dy in the low progesterone group, whereas it decreased (3.5 +/- 0.2 UC/min) in the high progesterone group (P < 0.001), and was negatively correlated with progesterone concentrations (I = -0.56; P < 0.001), No influence of oe stradiol on UC was noticed, These observations confirm the utero-relaxing e ffects of progesterone in the non-pregnant uterus and support the administr ation of progesterone before embryo transfer to increase tissue concentrati ons and improve the outcome of IVF.