title: Pregnancy rates after transfer of embryos obtained from different stimulation protocols and frozen at either pronucleate or multicellular stages.
abstract: After in-vitro fertilization, 2161 supernumerary embryos were frozen with 1,2-propanediol and sucrose as cryoprotectants at either pronucleate or multicellular (2-6 blastomeres) stages. By the end of March 1990, 494 pronucleate stage embryos and 492 multicellular stage embryos had been thawed and 54 and 47% of them, respectively were considered suitable for transfer. Ongoing pregnancy and implantation rates were 17.9 and 10.7%, respectively for embryos frozen at the pronucleate stage and 5.5 and 4.7% for embryos frozen at the multicellular stage. Ovarian stimulation with human menopausal gonadotrophin (HMG) after pharmacological hypophysectomy with a gonadotrophin releasing hormone agonistic analogue (GnRHa) using a long protocol permitted us to freeze significantly more embryos per cycle (7.2 +/- 4.1) than stimulation with HMG and GnRHa in a short protocol (4.7 +/- 3.4) or stimulation with clomiphene citrate (CC) and HMG (2.7 +/- 1.9). Ongoing pregnancy rates after transfer during the stimulated cycles were similar for the three types of treatment (27.1, 27.3 and 32.1%, respectively). However, ongoing pregnancy rates after frozen-thawed embryo transfers were significantly higher when originating from GnRHa + HMG treatments (14.3 and 14.8%, respectively for long and short protocols) than when originating from CC + HMG treatment (5.6%). Embryo cryopreservation has permitted the ongoing pregnancy rate to increase from 28.4 to 36.9% (P less than 0.01) even though more than half of the embryos have not been thawed. We conclude that embryos obtained after stimulation with GnRHa + HMG and frozen at the pronucleate stage are more likely to result in a pregnancy.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Liège, Hôpital de la Citadelle, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Demoulin
authors.forename: C
authors.initials: C
authors.lastname: Jouan
authors.forename: C
authors.initials: C
authors.lastname: Gerday
authors.forename: M
authors.initials: M
authors.lastname: Dubois
mesh_terms: D015925:Cryopreservation; D004624:Embryo Transfer; D005314:Embryonic and Fetal Development / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D010062:Ovulation Induction / Q000379:methods*; D011247:Pregnancy / Q000706:statistics & numerical data*; D012189:Retrospective Studies