Study group - Patients in the study group will receive additional two injections - the first - recombinant hCG 250 mcg (Ovitrelle; Merck Serono) on the transfer day and the second - GnRH-agonist 0.1 mg (Decapeptyl; Ferring Pharmaceuticals Israel) 4 days after the embryo transfer day. Patients in the control group will receive no injection.