Cytological and epidemiological findings in trisomies 13, 18, and 21: England and Wales 2004-2009.

This study describes the cytological and epidemiological findings in 985 trisomy 13 and 2512 trisomy 18 compared with 10,255 trisomy 21 diagnoses between 2004 and 2009 included in the National Down Syndrome Cytogenetic Register of England and Wales. The frequency of occurrence, proportions diagnosed prenatally, sex ratios, mean maternal age, and proportions of mothers with recurrences were analyzed. Ninety-seven, 98%, and 92% were free karyotypes for trisomy 21, 18, and 13, respectively; 3% of 21, 1% of 18, and 8% of trisomy 13 were translocations; and under 1% of trisomies 21 and 18 were double or triple aneuploids.

Cytogenetic and epidemiological findings in Down syndrome: England and Wales 1989-2009.

This study describes the characteristics of karyotypes leading to phenotypic Down syndrome (trisomy 21) in 29,256 cases diagnosed between 1989 and 2009 in England and Wales included in the National Down Syndrome Cytogenetic Register (NDSCR). The frequency of occurrence of the different karyotypes, proportions diagnosed prenatally, sex ratios, mean maternal age, and proportions of mothers with recurrences were analyzed. Nearly 97% of all cases were free trisomy 21; 2.

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.

Prenatal screening for Down syndrome in England and Wales and population-based birth outcomes.

Objective: Whether the introduction of antenatal screening for Down syndrome in England and Wales with serum biochemistry or ultrasound has led to improvements in patient outcomes is unknown. The purpose of this study was to relate pregnancy outcomes to the dominant method used for prenatal Down syndrome screening.

Study Design: For the years 1989 through 1999, England and Wales were divided into geographically defined areas where specific hospitals, health authorities, and cytogenetic laboratories provided maternity care for well-defined populations.