Adding GnRH agonists in the luteal phase has recently been said to improve implantation in IVF treatment (increased rates of pregnancy and birth). Adding GnRH agonists could also be beneficial for frozen-thawed embryo transfers. The objective was to compare the administration of Gonadotropin Releasing Hormone (GnRH) agonists during implantation with usual progesterone supplementation in the artificial cycle of frozen-thawed embryo transfers.A prospective randomized controlled trial was conducted in a reproductive medicine center in a university hospital including all women starting an artificial cycle of Frozen-Thawed Embryo Transfers (FET). Two hundred and twenty women were randomized from September 2013 to June 2014. In the addition of GnRh agonists' group, two triptorelin injections of 0.1mg were carried out on the 4th day and on the 6th day following the introduction of progesterone. The primary outcome was the ongoing pregnancy rate.The ongoing pregnancy rate was higher (17 % versus 10.6 % P=0.29) when triptorelin was added, although the difference wasn't significant for the population as a whole. The increase proved to be significant in the case of day 2 embryos (34.6 % versus 10.3 % P0.05) and of vitrified blastocysts (33.3% versus 12.5% P0.05).The ongoing pregnancy rate for day 2 embryos and vitrified blastocysts significantly increased when GnRH agonists were added during implantation.
