Maternal age-specific fetal loss rates in Down syndrome pregnancies.

Objectives: Pregnancies affected by Down syndrome (DS) have a greater risk of spontaneous fetal loss than those that are unaffected. In this article, we investigate the relationship between maternal age and the risk of spontaneous fetal loss in DS pregnancies.

Methods: Fetal loss at different maternal ages were estimated by survival analysis using follow-up of 5177 prenatally diagnosed cases.

Epidemiology of double aneuploidies involving chromosome 21 and the sex chromosomes.

The chance of two chromosome abnormalities occurring in one conceptus is very small. However, some authors have suggested that double aneuplodies (DAs) might be more common than the product of their individual frequencies. The nonrandomness of such DA events was considered to be evidence that nondisjunction (NDJ) may be genetically determined.