In Vitro Fertilization Outcomes Following Assisted Hatching of Embryos with Thick Zona Pellucida—A Prospective Randomized Study

Mara Koifman,Shirly Lahav-Baratz,Blais Idit,Libby Shopen,Ron Auslender,Martha Dirnfeld,Zofnat Wiener-Megnazi,David Ishai

doi:10.4236/arsci.2014.24009

Mara Koifman, Shirly Lahav-Baratz + Show 6 more

Open Access

https://doi.org/10.4236/arsci.2014.24009

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Abstract

Purpose: Impaired hatching is associated with implantation failure following in vitro fertilization (IVF). Thickening or hardening of the zona pellucida (ZP) has been proposed as a factor in this impairment. We examined whether selective assisted hatching (AH) is beneficial with embryos having a thick ZP. Methods: This prospective, randomized controlled study was performed in the IVF unit of an obstetrics and gynecology department in a university-affiliated hospital. Only patients undergoing IVF and having a ZP thickness of ≥17 μm measured in all their embryos were included. In the intervention group, AH was applied to all embryos, before their transfer. In the control group, embryos were transferred without AH. Implantation, clinical pregnancy and live birth rates were the study endpoints. Results: Both study arms were comparable in most baseline parameters. The two groups did not differ in implantation rates (14.1% control vs. 8.92% intervention, odds ratio (OR) = 0.5974, 95% confidence interval (CI) 0.325 - 1.1), clinical pregnancy rates (36.7% vs. 25.8%, OR = 0.6025, 95% CI 0.274 - 1.325), or live birth rates (25% vs. 18.9%, OR = 0.7021, 95% CI 0.291 - 1.691). Conclusions: Selecting embryos for AH by their ZP thickness as a sole parameter was not found to be beneficial and to improve IVF outcome.

Highlights

A key event for successful embryo implantation is the expansion and thinning of the zona pellucida (ZP) and embryonic hatching [1]
Hormonal factors including basal follicle stimulating hormone (FSH) and pre-ovulatory estrogen levels are associated with thick ZP [1] [3], and some studies have reported a direct relationship between the number of human menopausal gonadotropin ampoules given for ovarian stimulation and ZP thickness [3]
The outcome follow-up for the frozen-thawed embryos continued until 2012. Both of the study arms were comparable in terms of indications for in vitro fertilization (IVF), number of previous treatment cycles, day 3 FSH levels, smoking habits, number of administered human menopausal gonadotropin (hMG) ampoules, and mean ZP thickness (Table 1)

Summary

Introduction

A key event for successful embryo implantation is the expansion and thinning of the zona pellucida (ZP) and embryonic hatching [1]. Studies in women undergoing in vitro fertilization (IVF) have shown that maternal factors such as advanced age and active or passive smoking correlate with a thicker ZP [1] [2]. The assisted hatching (AH) procedure, first introduced in 1990 by Cohen et al [5], targets improvement in IVF implantation rates by thinning, drilling, or completely removing the ZP before embryo transfer. According to the American Society for Reproductive Medicine committee opinion from 2008 [6], the available published data do not support routine or universal application of AH in IVF cycles, but AH may be clinically useful in patients with a poor prognosis, including those with ≥2 failed IVF cycles, poor embryo quality, and advanced maternal age (≥38 years of age)

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