It has also been repeatedly postulated that impaired peristalsis interferes with implantation of the embryo, yet Martinez-Conejero published a trial that showed a higher incidence of miscarriage, but no effect on embryo implantation in women undergoing oocyte donation. This might either indicate that the postulated effect of peristalsis is wrong or, more likely, since this is a study in an IVF setting, that hormonal treatment with gonadotropin-releasing hormone (GnRH)-agonist could improve implantation.