Uterine contractility and embryo implantation.

PURPOSE OF REVIEW: The aim of this article is to assess the importance of uterine contractility in the implantation of human embryos. RECENT
FINDINGS: Recent findings show that the receptive phase of the endometrium seems to occur in close association with the appearance of pinopodes and endometrial integrins that may be activated by the IL-1 system. Throughout the menstrual cycle wavelike activity patterns of the uterus were identified with adequate wave patterns appearing to be related to successful reproduction in spontaneous cycles and in assisted reproduction. Such patterns are controlled by steroid hormones. Embryo attachment to the predecidualized endometrium and its invasion may be determined by the expression of proteolytic enzymes that require uterine quiescence for implantation. The uterine activity was detected both in vitro and in vivo by using invasive intrauterine pressure and noninvasive ultrasound approaches. Progesterone promotes local vasodilatation and uterine musculature quiescence by inducing nitric oxide synthesis in the decidua. At present, until new evidence emerges to demonstrate otherwise, the effects of progesterone are, directly or indirectly, the only determinant of endometrial preparation for embryo nidation, with the induction of uterine quiescence being one of these effects.
SUMMARY: Adequate uterine contractility may provide for gamete/embryo transportation through the utero-tubal cavities and successful embryo implantation in spontaneous or assisted reproduction. Inadequate uterine contractility may lead to ectopic pregnancies, miscarriages, retrograde bleeding with dysmenorrhea and endometriosis.