Major decrease in the incidence of trisomy 21 at birth in south Belgium: mass impact of triple test?

Abstract

In South Belgium (Wallonia), the 'triple test' was introduced in 1990-1991, and is nowadays a widely accepted screening method for assessment of trisomy 21 risk in pregnancy. The 'triple test' is not regulated and can be freely performed by any biomedical lab, making epidemiological data unavailable. By contrast, cytogenetic investigations are limited to a few genetic centres, and accurate statistics can be easily built from their files. During the period 1984-1989, a total of 244 trisomy 21 (1/876 pregnancies) were diagnosed in the Genetic Centres of Liège and Loverval, 42 (17%) of them prenatally. During the period 1993-1998, 294 trisomy 21 (1/704 pregnancies) were observed, 165 (56%) of which prenatally, and more than 90% of affected pregnancies were terminated. Even after correction for late foetal loss of trisomic foetuses, the difference is highly significant, and corresponds to a theoretical shift in the incidence of trisomy 21 at birth from 1/794 to 1/1606. As no remarkable progress occurred in other non-invasive prenatal screening procedures or general health care policies in Belgium, the most reasonable explanation is the use on a large scale of triple test by pregnant women, and the election of termination for most affected pregnancies.

Live birth prevalence of Down syndrome in Tottori, Japan, 1980–1999

“…The recent introduction of prenatal diagnoses, such as triplemarker tests and amniocentesis, has dramatically reduced the live birth prevalence of Down syndrome (DS) in many Western countries [Bishop et al, 1997;Cheffins et al, 2000;Verloes et al, 2001;Egan et al, 2004]. In contrast, an increase in live birth prevalence of this syndrome has been reported in Japan [Hoshi et al, 1999;Seto et al, 2003].…”

Perinatal Loss of Ts65Dn Down Syndrome Mice

“…Improved detection methods including serum screening (maternal serum a-fetoprotein, estriol, and human chorionic gonadotropin) and fetal ultrasound may increase prenatal ascertainment. It has been conclusively shown that increasing maternal age strongly correlates with the incidence of DS (Verloes et al 2001;Forrester and Merz 2002;Bell et al 2003;Khoshnood et al 2004). Trisomy 21 is the most frequently viable autosomal aneuploidy at birth.…”

“…The incidence of DS is 1 in 800-1000 live births; the total prevalence of DS (number of affected cases in live births, stillbirths, and terminations) appears to be steady or rising (Leonard et al 2000;Verloes et al 2001;Forrester and Merz 2002;Bell et al 2003;Roizen and Patterson 2003;Khoshnood et al 2004). Improved detection methods including serum screening (maternal serum a-fetoprotein, estriol, and human chorionic gonadotropin) and fetal ultrasound may increase prenatal ascertainment.…”

Clinical and Economic Impact of Adopting Noninvasive Prenatal Testing as a Primary Screening Method for Fetal Aneuploidies in the General Pregnancy Population

“…The most frequently used approach is first-trimester screening (FTS), which combines nuchal translucency (NT) ultrasound measurement and maternal serum testing to assess the levels of human chorionic gonadotropin (hCG) and pregnancyassociated plasma protein A in combination with age and medical history [1,2]. The triple test (hCG, alpha-fetoprotein, and unconjugated estriol) is used to screen women presenting in the second trimester [3].…”