The effect of pronuclear morphology on early development and chromosomal abnormalities in cleavage-stage embryos.

BACKGROUND Pronuclear (PN) zygote morphology has been proposed as a useful tool for selecting the best embryos for transfer. METHODS PN morphology was recorded in 888 zygotes and classified according to similar/different PN size [groups A (n = 816) and B (n = 72)] and to the number, distribution and synchrony of nucleolar precursor bodies (NPB): subgroup I, pronuclei with 3-4 polarized NPB; subgroup II, 5-7 synchronic polarized NPB or 7-10 NPB distributed randomly; and subgroup III, morphologies other than those of groups I or II. Embryo development and chromosomal abnormalities were evaluated for each PN pattern. RESULTS In patients aged 37 years, statistical differences among groups were not observed. CONCLUSIONS In patients aged 37 years, this correlation does not exist.