Outcome of the fetuses with severely increased nuchal translucency thickness in the first trimester

To study the outcome of pregnancies with severely increased nuchal translucency (NT) thickness at the 11-13-week scan.

This study included 162 singleton pregnancies whose fetuses had increased NT thickness ≥ 5.5 mm between September 2013 and August 2018. The cases were divided into two groups: NT ≥ 6.5 mm (n = 112) (group A); and 6.5 mm > NT ≥ 5.5 mm (n = 50) (group B). Fetal (amniotic fluid) or placental (chorionic villous) chromosome analyses were conducted. Subsequent ultrasound findings, pregnancy outcome and structural defects in the neonates were recorded and analyzed.

Abnormal karyotype was found in 71% (60/84) (group A) and 57% (21/37) (group B) of the cases respectively. In group A, 15 cases out of 24 with normal karyotype were born. Among these 15 cases, one case died soon after birth and 5 cases had associated abnormalities. In group B, 13 cases out of 18 with normal karyotype or negative noninvasive prenatal testing results and 1 case out of 2 cases with 47,XXY were born. All of them survived with no major anomaly.

Incidence of chromosomal aberrations was high in the cases with severely increased NT thickness. But favorable outcome could be expected if the fetus had no chromosomal abnormality and no abnormal findings were found in second trimester ultrasound scan especially in a fetus with increased NT < 6.5 mm.