Coculture of human zygotes on fetal bovine uterine fibroblasts: embryonic morphology and implantation.

Zygotes from in vitro fertilization patients (n = 116) were randomly allocated to culture in either conventional plastic petri dishes or coculture on a monolayer of fetal bovine uterine fibroblasts. Embryos (n = 288) remained 26 to 32 hours in these culture systems. Video tape recording for later morphological analysis (11 parameters) was performed on 117 conventionally cultured and 104 cocultured embryos, shortly before replacement, by an independent observer, unaware of the culture conditions for each embryo. A significantly greater number of cocultured embryos (52%) had "good" morphology (zero or only one abnormal characteristic) as compared with conventionally cultured embryos (30%). The most outstanding morphological characteristic of cocultured embryos was the expanded appearance of their blastomeres. The incidence of implantation per embryo increased from 13% to 19% when the coculture rather than conventional culture system was used, and the incidence of ongoing pregnancy per patient after coculture doubled to 35%.