First trimester screening by ultrasound : audit on the use of first trimester fetal nuchal translucency in the detection of chromosomal defects

Abstract EN

Objective : To evaluate screening for chromosomal defects by a combination of fetal nuchal translucency thickness and maternal age.

Methods : Five thousand and sixty two women with singleton pregnancies were screened at 10-14 weeks gestation from 1 July 1994 to 22 January 1996 at Queen Mary's Side up NHS Trust, Side up, Kent, England (District General Hospital).

Trisomy 21 and other chromosomal defects were identified by increased nuchal translucency thickness > 3.5 mm and maternal age- Results : During the study period, the total number of pregnancies was 6643.

A total of1378 (20.7 %) women presented too early or too late or they declined risk assessment.

Another group of women of203 (3.1 %) presented with missed abortion and twins.

The number of alive singletons examined was 5062, therefore, successful uptake of the first trimester scan was 76.2 %.

Using a cut-off point of a risk of more than 1 in .300 based on nuchal translucency and maternal age, seven of the eight (87.5 %) pregnancies with trisomy 21 and fifteen of the sixteen (93.8 %) pregnancies with all chromosomal abnormalities were detected In the completed pregnancies of 3112, three of four pregnancies with trisomy 21 and seven of eight pregnancies with all chromosomal abnormalities were investigated Conclusion : First trimester screening by ultrasound is feasible and the combination of maternal age and fetal nuchal translucency thickness at 10-14 weeks can be a useful method of screening for Down syndrome and other chromosomal abnormalities.