Analysis of fetal death in relation with increased fetal nuchal translucency thickness in the south of Vietnam

Objectives: The aim of this study was to investigate the fetal deaths relation with an increased fetal nuchal translucency (NT) thickness in the South of Vietnam.

Methods: A total of 2500 singleton pregnancies were measured fetal NT thickness and performed free beta subunit of human Chorionic Gonadotropin (free β-hCG) and pregnancy associated plasma protein-A (PAPP-A) routinely in the first trimester, then scanned systematically for fetal structure by ultrasonography at the second trimester of gestation, next followed to their delivery and examined neonatal status. For suspicion of fetal abnormality, amniocentesis was indicated to confirm a fetal karyotype. Fetal abnormal chromosome was counselled a termination of pregnancy (TOP). 5 groups of fetal NT thickness was divided: group of normal fetal NT thickness (< 2.4mm), group of mild increased of fetal NT thickness (2.4-3.4mm), group of moderate increased fetal NT (3.5-4.4mm), group of severe fetal NT (4.5-5.4mm) and group of very severe fetal NT (≥ 5.5mm). We evaluated the fetal deaths (included spontaneous abortion, fetal death intra-uterine, and terminated pregnancy due to aneuploidy and/or structural abnormality), then look for a relation between an increased fetal NT thickness and those fetal adverse outcomes.

Results: Fetal NT thickness cut-off point at 2.4mm or more was defined as an increased fetal NT thickness with 65.5% of sensitivity for fetal abnormal detection. 5.3% (133/2500) was the prevalence of increased fetal NT thickness. 2.8% (71/2500) of cases had been indicated an amniocentesis. A total incidence of fetal death was found 1.5% (37/2500). In group of fetal NT thickness < 2.4mm, the rate of abnormal karyotype was 0.4% (10/2367), none case of fetal deaths obtained. In the fetal NT group of 2.4-3.4mm, total of fetal death found 26.4% (32/121) that included 12.4% (15/121) of abnormal karyotype, 8.3% (10/121) of abnormal ultrasound scanning, 5.8% (7/121) of fetal demised, and 0.8% (1 case) of neonatal defect due to G6PD deficiency. In the group of 3.5-4.4mm, 33.3% (3/9) of fetuses were died (22.2% was due to aneuploidy and 11.1% was due to miscarriage spontaneously). In the group of 4.5-5.4mm, 1 case (50%) of trisomy 18 was detected and in the group of ≥ 5.5mm, 1 case (100%) of trisomy 21 had been diagnosed. When fetal NT thickness increased, the possibility of fetal demised was higher significantly: likelihood ratio (LR) augmented from 15.2 in the fetal NT group at 2.4-3.4mm to 169.5 in fetal NT group at ≥ 5.5mm (p < 0.01, Pearson chi2).

Conclusion: An increased fetal NT thickness was useful finding for prediction of fetal deaths (included fetal abortion, demised or terminated) in the prenatal diagnosis and care program in the South of Vietnam.