First-trimester prenatal diagnosis performed on pregnant women with fetal ultrasound abnormalities: the reliability of interphase fluorescence in situ hybridization (FISH) on mesenchymal core for the main aneuploidies

Abstract

Objectives: To examine the reliability of interphase FISH analysis of the main aneuploidies performed on mesenchymal core when prenatal diagnosis was performed on pregnant women with first-trimester fetal abnormalities on ultrasound.

Study design: 386 first-trimester prenatal examinations were investigated from chorionic villus samplings for increased nuchal translucencies or other fetal ultrasound abnormalities. Interphase fluorescence in situ hybridization (FISH) for the main aneuploidies (trisomies 13, 18, 21 and gonosomal aneuploidies) was performed on the mesenchymal core of villi. Molecular cytogenetic results were always complemented by conventional cytogenetic results on long-term cultured villi (LTC-villi). Short-term cultured villi (STC-villi) preparations were retrospectively performed only when a chromosomal abnormality was observed with interphase FISH and/or LTC-villi.

Results: 88 chromosomal abnormalities (88/386=22.8% of first-trimester diagnoses) which could discuss subsequent abortions were observed after LTC-villi preparations. All cases possibly detectable by interphase FISH were detected. Thus, 85 aneuploidies (85/386=22.0% of first-trimester diagnoses; 85/88=96.6% of chromosomal abnormalities) were detected by interphase FISH, allowing early abortion by curettage before week 14 amenorrhea. No discrepancy occurred between interphase FISH and LTC-villi results for the aneuploidies studied. Three false-negative results (3/386=0.77% of first-trimester diagnoses; 3/88=3.41% of chromosomal abnormalities) were observed with STC-villi.

Conclusion: We observed a high rate of false-negative results on cytotrophoblast cells. Conversely, interphase FISH of the main aneuploidies on the mesenchymal core provided rapid and reliable results, and therefore should be preferred to STC-villi in first-trimester prenatal diagnosis performed on pregnant women with fetal abnormalities on ultrasound.