The possibility of noninvasively assessing uterine contractility in ultrasound scans allows improvements in our understanding of hormonal regulation and of the influence of uterine contractility on the human embryo implantation process in natural and controlled ovarian hyperstimulation cycles. Ultrasound is a reliable tool for studying contractions of the nonpregnant uterus and confirms that uterine contractility is influenced by ovarian hormones and indicate that it partakes in the embryo implantation process in humans.