Assisted Hatching of the Zona Pellucida Prior to Embryo Transfer in Fresh Donor Egg IVF Cycles

Abstract

The early embryo is surrounded by the zona pellucida (ZP). Prior to implantation, the blastocyst must “hatch” out of the ZP so that implantation can occur. A variety of factors may influence the ability of the blastocyst to accomplish hatching and if so influence the chances for pregnancy occurring. Assisted hatching in in vitro fertilization cycles may improve the likelihood of implantation and pregnancy in certain age groups but it has not been well described in a donor/recipient IVF population. The purpose of the study was to evaluate the effectiveness of day 5 assisted hatching of the zona pellucida prior to fresh embryo transfer in donor recipients. This study was a retrospective case-control analysis of patients who underwent a fresh IVF cycle using donor eggs. The control group of 192 patients had embryos transferred prior to the implementation of assisted hatching of the ZP at our center in 2009 and 127 patients had an embryo transfer after assisted hatching of the ZP with CO2 laser during 2010. Cases and controls were compared using t-test and chi squared analyses. There were no significant differences in age (41.5 vs 41.4 years), race, estradiol levels of the donor at the time of hCG administration (4130pg/ml vs 3965pg/ml), number of oocytes retrieved (23.5 vs 23.9) or M2s undergoing itracytoplasmic sperm injection (ICSI) (18.3 vs 18.9), number of oocytes fertilized (15.0 vs 16.1), blastocyst formation (9.2 vs 9.5) or the number of embryos transferred (1.66 vs 1.6). There was no difference in the biochemical pregnancy rate (78.7% vs 79.7%) or the number of gestational sacs (1.17 vs1.14). There was a non-statistically significant trend toward an increased probability of observing a fetal heartbeat (78.7% vs 76.6%, P=0.65) but a trend toward an increase in live birth (75.6% vs 69.8%, P=0.25) in cases versus controls. (Table1)Table 1Hatched (n=127)Controls (n=192)P valueChemical pregnancy rate78.7%79.7%0.83Number of gestational sacs1.171.140.70Clinical pregnancy rate78.7%76.7%0.65Live birth or continuing pregnancy75.6%69.8%0.25 Open table in a new tab This study is the first to evaluate the use of assisted hatching in donor egg IVF cycles. Day 5 Laser-assisted hatching of the zona pellucida prior to embryo transfer in donor IVF cycles may improve clinical pregnancy and live birth rates.