4. Assisted zonal hatching (AZH) or transfer of zona-free embryos?
Assisted zona hatching (AZH) has being used in IVF programmes for several years and controversially discussed with respect to its benefit to increase pregnancy rates in elder women. Recently, successful pregnancies have been reported after transfer of zona-free blastocysts. It was the study of Mansour and co-workers to evaluate outcomes after transfer of zona-free day 3 embryos. Two groups of women undergoing ICSI were included in the study. Group A consisted of 52 women under the age of 40 years undergoing their first ICSI attempt. They were alternately randomized to receive zona-free embryos (27 women) and zona-intact embryos (25 Women). The second group (group B) included 71 women with a poor prognosis, as defined by age 40 years or more, and/or at least two previously failed IVF/ICSI attempts. They were randomized in a 3:4 ratio (30 zona-free, 41 zona intact). Acid Tyrodeâ€™s solution was used to remove the zona pellucida before embryo transfer on day 3 after oocyte collection. The pregnancy rate in group A was not significantly improved when the zona pellucida was removed. However, in the poor prognosis group B, zonal removal resulted in a significantly higher pregnancy rate when compared with controls (23 versus 7.3%). We conclude that complete removal of the zona pellucida can improve pregnancy rates in women with poor IVF/ICSI prognosis. There was no indication that zona pellucida removal increased the chance of monocygotic twinning.
Mansour RT, Rhodes CA, Aboulgar MA, Serour GI, Kamal A (2000) Transfer of zona-free embryos improves outcome in poor prognosis patients: a prospective randomized controlled study. Hum. Reprod. 15: 1061-1064