ABSTRACT

The fact that chromosomal abnormalities in the female gamete originate predominantly from errors in meiosis is well known. Studies using DNA polymorphism performed in families with aneuploid spontaneous abortions or liveborn babies with common chromosomal syndromes demonstrate that these abnormalities derive mainly from meiosis I.1-3

It has been suggested that the age-related increase in the incidence of common trisomies is probably determined by an age-related reduction in meiotic recombination, resulting in a premature separation of bivalents and chromosomal non-disjunction. Meiosis II errors may also be related to errors involving an increased rate of meiotic recombination during meiosis I, which may result in a failure of bivalents to separate.4