Uterine contractility decreases at the time of blastocyst transfers

High-frequency uterine contractions at the time of non-cavitating embryo tr ansfer influence adversely IVE-embryo transfer outcome. This prompted us to quantify prospectively the possible decline in uterine contraction frequen cy occurring during later stages of the luteal phase of ovarian stimulation , up to the time of blastocyst transfers, in 43 IVF-embryo transfer candida tes. Contractility was assessed on the day of human chorionic gonadotrophin (HCG) administration, 4 days after HCG (non-cavitating embryo transfer; HC G + 4), and 7 days after HCG (blastocyst transfers; HCG + 7), For this, 2 m in sagittal uterine scans were obtained by ultrasound and digitized with a computerized system for the assessment of uterine contraction frequency. Ou r results indicated that a slight, yet significant, decrease in uterine con traction frequency, observed from the day of HCG (4.4 +/- 0.2 contractions/ min) to HCG + 4 (3.5 + 0.2 contractions/min), was followed by a more pronou nced, additional decrease between HCG + 4 and HCG + 7 (1.5 +/- 0.2 contract ions/min; P < 0.001), In conclusion, during the luteal phase of ovarian sti mulation, uterine contractility decreases progressively, and reaches a near ly quiescent status 7 days after HCG administration, at the time of blastoc yst transfers. It is possible that such a uterine relaxation assists blasto cyst implantation.