1ST-TRIMESTER ULTRASOUND SCREENING FOR FETAL ANEUPLOIDIES IN WOMEN OVER 35 AND UNDER 35 YEARS OF AGE

In a prospective screening study, the utility of the thickness of firs t-trimester simple hygroma in sonographic screening for fetal chromoso mal abberrations was examined. A total of 3380 women, 1280 of whom wer e 35 years or over, and 2100 of whom were under 35 years, were screene d by ultrasound at 9-12 weeks of gestation. The thickness of fetal nuc hal simple hygroma was measured. Women over 35 years of age underwent transabdominal chorionic villus sampling (CVS). In women under 35 year s of age, CVS was offered only if the thickness of nuchal hygroma was at least 3 mm, or in cases of parental chromosomal abnormalities. A to tal of 46 chromosomal anomalies were detected, of which 43 (93.5%) sho wed simple hygroma. The incidence of first-trimester simple nuchal hyg roma in pregnancies of women over 35 and under 35 years of age was 5.4 % (69 cases) and 1.28% (27 cases), respectively, and the percentage of chromosomal abnormalities was 2.9% and 0.43%, respectively. The risks of trisomies and poor pregnancy outcome were increased at larger size s of first-trimester simple hygroma. A sensitivity of 93.5% and a spec ificity of 98.4% of the method were found. Using a measurement of firs t-trimester simple hygroma of greater-than-or-equal-to 3 mm to identif y pregnancies at risk for chromosomal anomalies at 9-12 weeks of pregn ancy is a useful method for selection of women with high and low risk for aneuploidy.