Pregnancy following fertilization of zona-free, coronal cell intact human ova: Case Report

A pregnancy by intracytoplasmic sperm injection (ICSI) of a couple whose oocytes were recovered without a zona pellucida is reported. Previous IVF/ICSI cycles indicated all oocytes had either very thin or no zona pellucida at the time of cumulus removal prior to ICSI. As a result, many ova were very fragile and lysed upon handling. In the latest attempt, six ova were recovered. After coronal cell dissection of two ova where both lacked a zona pellucida and one lysed, it was elected to attempt to inject the remaining four ova without removal of their coronal cells. The zona pellucida was not visible through the cell layer and the position of the polar body in three ova was speculative. Two embryos possessed normal pronuclei on day 1, and displayed six blastomeres prior to transfer on day 3. During preparation for transfer, sufficient coronal cells fell away to confirm both embryos lacked a zona pellucida. Pregnancy was confirmed by ultrasound observation of a fetal heart 4 weeks later. This report documents that where the zona pellucida is absent, the coronal cells provide sufficient support to maintain blastomere interaction and embryo viability and the zona pellucida is not essential for early embryo development and pregnancy.