Maternal age specific rates for chromosome aberrations and factors influencing them: Report of a collaborative european study on 52 965 amniocenteses

TLDR

The study postulates that maternal age effects, higher spontaneous abortion rates with age, and increased early abortion probability for heavily imbalanced conceptions explain the observed chromosomal aberration patterns. A stepwise logistic regression of 13,299 pregnancies with known parental ages showed that paternal age does not influence maternal age specific rates, except possibly for 47,XXY, supporting the proposed mechanisms. Maternal age specific rates for major chromosome aberrations were determined in 52,965 pregnancies; rates rise exponentially with age for trisomies 21, 18, 13, XXX, XXY, plateau for autosomal trisomies, and decline with age for 45,X.

Abstract

Abstract Maternal age specific rates for all major chromosome aberrations have been determined in 52 965 pregnancies in mothers 35 years of age and over at the time of amniocentesis. Rates increase exponentially with advancing maternal age for trisomies 21, 18 and 13, and for the XXX and XXY syndromes, but in the autosomal trisomies this rise appears to be followed by a levelling off at the upper end of the age range. A significant inverse relationship with maternal age is found for 45,X cases. It is postulated that these various patterns are the result of the interaction of three principal factors: a maternal age effect acting particularly on first meiotic nondisjunction: a higher spontaneous abortion rate with advancing maternal age for aneuploid as compared to euploid conceptions; and an increased probability of spontaneous abortion before the time of amniocentesis for conceptions with more extensive chromosome imbalance. A stepwise logistic regression analysis of 13 299 pregnancies in which both parental ages are known shows that the father's age does not influence these maternal age specific rates, with the possible exception of the 47,XXY syndrome.