Influence of in vitro systems on embryo survival and fetal development in cattle.

In vitro systems are commonly used for the production of bovine embryos. Comparisons between in vivo and in vitro produced embryos illustrate that the morphology of preimplantation-stage embryos differ significantly, the survival of embryos and fetuses is decreased, the size distributions of the populations of conceptuses and fetuses are altered throughout gestation, and placental development is significantly changed. Taken together these findings indicate that exposure to some in vitro environments during the first 7 days of life can profoundly influence fetal and placental development in cattle. An understanding of how in vitro oocyte maturation, in vitro fertilization, and embryo culture systems influence both fetal and placental development should result in systems that consistently produce normal embryos, fetuses, and calves.