P031: Nuchal translucency measurement screening for aneuploidy at 11-14 weeks?first experiences from Turku, Finland Feto-maternal ultrasound unit of Turku Health Center and prenatal outpatient department of Turku City Hospital

Abstract

To study the value of the nuchal translucency (NT) measurement in screening for chromosomal abnormalities by ultrasound at 11–14 weeks of gestation and to compare 95% reference ranges with the ranges of 99% (Braith-waite et al. 1996). A total of 1540 fetuses were consecutively studied with NT measurement in an unselected population from March 2001 up to June 2002. Reference range of 99% was used in 705 fetuses and 95% range in 835 fetuses. When using 99% range the second trimester DS screening (s-AFP and hCG) was also offered, if NT was between 95 and 99% ranges. Crown rump measure (crl) was measured and pregnancy was dated. Amniocentesis was offered when NT was over reference ranges. All newborns were physically examined for major chromosomal anomalies up to April, 2003. There were no statistical differences between the 99 and 95% groups regarding pregnant women's mean age (28 vs. 28 yrs), crl (59 vs. 62 mm), pregnancy length (12 + 2 vs. 12 + 5 weeks) or NT (1.2 vs. 1.3 mm). NT was above 99% range in 2.3% of fetuses (16/705) and above 95% range in 5.6% (48/835) (P < 0.05). Four DSs and one trisomy 18 were found. Two DSs were found in 95% group (the mothers 32 and 34 yrs, NT 2.4 and 3.1 mm). One trisomy 18 was found in 99% group (the mother 32 yrs, NT 4.0 mm). In 99% group one 38 years old woman with 2.6 mm NT a positive trisomy test was recognised and amniocentesis confirmed DS. Only one DS newborn (NT 1.6 mm) was delivered by a 38-year old woman. For age of 38 yrs an amniocentesis was offered, but she refused. No pregnancy losses were associated with 61 amniocentesis procedures. NT screening with only 99% reference range doesn't seem to be sufficient to find out chromosomal abnormalities; two chromosomal abnormalities should have been detected from the whole studied population. Reference range of 95% served clearly better; that range should have detected four out of five chromosomal abnormalities.