Successful Pregnancy following Transfer of Embryo with Dissolved Zona Pellucida

This study aimed to describe a case of a patient with the spontaneous dissolution of zona pellucida(ZP)during cleavage embryo development after intracytoplasmic sperm injection(ICSI).This patient experienced early abortion due to fetal chromosome 8 abnormality and received ICSI at 31 years of age.Time-lapse monitoring of embryo cleavage and blastocyst culture was performed,and we found that the ZP of embryos 1,2,4,and 5 dissolved gradually during the cleavage stage of embryo development.Five blastocysts that developed from 2 pronuclear zygotes were analyzed using next-generation sequencing,and one frozen-thawed blastocyst was transferred,resulting in intrauterine pregnancy.The results of amniotic fluid puncture showed normal fetal chromosomes.To our knowledge,this is the first report of ZP dissolution during the cleavage-stage embryo;however,the exact mechanism remains unknown.The morphological changes inferred that the granular matter in the periocular space was related to the dissolution of ZP through time-lapse observation.