Transfer of zona-free embryos improves outcome in poor prognosis patients:a prospective randomized controlled study

Assisted zona hatching (AZH) has been used in IVF programmes for several ye ars. Recently one group has reported successful pregnancies after transfer of zona-free blastocysts. The aim of our study was to evaluate outcomes aft er transfer of zone-free day 3 embryos. Two groups of women undergoing intr acytoplasmic sperm injection (ICSI) were included in the study. Group A con sisted of 52 women under the age of 40 years undergoing their first ICSI at tempt. They were alternately randomized to receive zona-free embryos (27 wo men) and zona-intact embryos (25 women). The second group (group B) include d 71 women with a poor prognosis, as defined by age 40 years or more, and/o r at least two previous failed IVF/ICSI attempts. They were randomized in a 3:4 ratio (30 zona-free, 41 zona-intact). Acid Tyrode's solution was used to remove the zona pellucida before embryo transfer on day 3 after oocyte c ollection. The pregnancy rate in group A was not significantly improved whe n the zona pellucida was removed. However, in the poor prognosis group B, z ona removal resulted in a significantly higher pregnancy rate when compared with controls (23 versus 7.3%). We conclude that complete removal of the z ona pellucida can improve pregnancy rates in women with poor IVF/ICSI progn osis.