Advanced Maternal Age in Polyploidy With Concurrent Aneuploidy

摘要

TO THE EDITOR:Chromosome abnormalities occur in humans at a rate of approximately 1 in every 150 live births. They are seen in approximately 50% of first-trimester and 20% of second-trimester spontaneous abortions [Jorde et al., 2006]. Of all chromosome abnormalities, aneuploidy is the most common, occurring in 25% of miscarriages [Hassold et al., 1996]. Most aneuploidy is due to nondisjunction arising in oogenesis, which can occur during meiosis I or II. As a woman's age increases she has an increased risk of meiotic non-disjunction, resulting in aneuploidy and an increased risk of spontaneous abortion. In contrast to aneuploidy, increased maternal age is not a risk factor for polyploidies such as triploidy or tetraploidy [Eiben etal., 1990; Ford etal., 1996]. Determining which classes of chromosome abnormalities in products of conception are related to maternal age is an important factor in establishing accurate recurrence risk information for a woman for future pregnancies. In a small series, Ford et al. [1996] suggested that the maternal age distribution for cases with combined polyploidy— aneuploidy is very similar-to karyotypically normal cases. However, in such combined'cases, it is not known which anomaly arises first, that is, whether an aneuploid gamete occurs first followed by triploidy or tetraploidy, or whether a triploid or tetraploid zygote might occur followed by mitotic nondisjunction leading to aneuploidy. If aneuploidy arises first, there maybe a similar maternal age effect as seen in typical aneuploidy, and a similar small increased risk of aneuploidy in subsequent pregnancies [Warburton et al., 2004].