Authors: Souter I. (1), Hill DL. (2), Surrey MW (2). (1) University of California Los Angeles, California, USA Department of Obstetrics/Gynecology Division of Reproductive Endocrinology and Infertility (2) Southern California Reproductive Center, Beverly Hills, California, USA
Introduction: During in vitro fertilization-embryo transfer cycles (IVF-ET) many morphologically normal embryos fail to implant. One explanation for implantation failure is the existence of chromosomal aneuploidy, or single gene defects. The purpose of the present study was to assess the incidence of chromosomal abnormalities in morphologically normal embryos.
Materials and methods: Design: Retrospective analysis of 24 IVF-ET cycles in which preimplantation genetic diagnosis(PGD) was performed prior to embryo transfer.
Setting: Large private IVF center in California.
Methods: Fertilized embryos were analyzed on Day-3 post insemination. One blastomere was aspirated from embryos of good morphology (Grade A or B) at the 6-10 cell stage. Twenty-one cases were analyzed by fluorescence in situ hybridization (FISH) with chromosome specific probes. In 3 cases polar body biopsy was used in conjunction with polymerase chain reaction for detection of single gene defects.
Main outcome measure: Embryo morphology, FISH/PCR analysis of fixed blastomeres or polar bodies clinical pregnancies and implantation.
Results: 22 patients (average age: 37.8 years) underwent 24 IVF-ET/PGD cycles. In 7 cycles (29.2%) ICSI was performed. A total of 355 oocytes were produced, 245 (69%) oocytes fertilized and of them 156(63.7%) were considered morphologically suitable for biopsy. In 8 blastomeres, no result was obtained because of the absence of a nucleus. Of the remaining 148 embryos, 65 (43.9%) were chromosomally normal. Embryo transfer with at least one normal embryo was performed in 22 cycles.
Fifty-four chromosomally normal embryos were replaced. Eleven clinical and 4 biochemical pregnancies were generated for a clinical pregnancy rate of 50% per transfer. The rate of clinical pregnancy loss was 18.2% (9.1% if we exclude one pregnancy found at 11 weeks to be abnormal – chromosome two trisomy).
Conclusions: During IVP many good quality embryos are chromosomally abnormal. In older women, women with a history of pregnancies with aneuploid fetuses or multiple IVF failures, PGD may lead to an increased rate of implantation, and significantly reduce the risk of chromosomally unbalanced offspring and pregnancy loss. Expanding the indications for transferring only euploid embryos might reduce the need for repeated cycles of ovarian stimulation and egg retrieval, and improve pregnancy rates for all patients undergoing IVF.