ANALYSIS OF THE HUMAN ZONA-PELLUCIDA DURING CULTURE - CORRELATION WITH DIAGNOSIS AND THE PREOVULATORY HORMONAL ENVIRONMENT

Purpose: The objective of this study was to analyze sequentially the h uman zona pellucida changes in an in vitro fertilization program as it relates to several variables. Methods: The zona pellucida thickness w as measured daily in zygotes and cleavage-stage embryos on a Nikon inv erted microscope equipped with Hoffman modulation contrast optics, usi ng an ocular micrometer. A total of 512 embryos from 96 patients was e valuated. Results: There was a highly significant direct correlation b etween zona thickness and preovulatory estradiol and basal day 3 FSH l evels (P < 0.02 and P < 0.0006, respectively). This relationship showe d a rapid reversal following 48 hr of culture; embryos from patients w ith the highest FSH levels had thinner zonae prior to transfer (P < 0. 0007). The zonae from patients with unexplained infertility were thick er (19.4 +/- 2.7 mu m) than those from patients with endometriosis (17 .7 +/- 2.2 mu m), tubal (17.5 +/- 2.4 mu m), or male-factor infertilit y (16.4 +/- 2.7 mu m) (P < 0.0001) on the first day of culture. Conclu sions: We hypothesize that the thickness of the human zona pellucida i s influenced by the preovulatory hormonal environment and diagnosis. T hese factors should be considered as part of the embryo quality evalua tion prior to transfer or when assessing the possibility of using assi sted hatching. More studies are needed to understand the factors regul ating the thickness of the human zona pellucida.