Prenatal and perinatal outcomes of twin pregnancy discordant for one fetus with nuchal translucency above the 95th percentile.

OBJECTIVE

To compare prenatal and perinatal outcomes of twin pregnancies in which one twin the nuchal translucency (NT) was above the 95th percentile in dichorionic twins (DCT) and monochorionic twins (MCT).

METHOD

In this retrospective study, 93 twin pregnancies (186 fetuses) in which one twin the NT was above the 95th percentile and the co-twin had normal NT were analyzed. Results of of G-banding and Chromosomal microarray (CMA), ultrasound findings and pregnancy outcomes were reviewed.

RESULTS

Totally, 57 pregnancies (114 fetuses) were DCT and 36 pregnancies (72 fetuses) were MCT. Karyotyping and CMA results shown that clinically significant chromosomal abnormalities were found in 16 fetuses, including 13 aneuploidies, 2 chromosomal mosaic and 1 pathological Copy number variations (CNVs) (14 were DCT and 2 were MCT). Overall, the incidence of fetal chromosomal abnormalities was 12.3% (14/114) in DCT and 2.8%(2/72) in MCT (χ = 3.932,  = 0.047). Among the cases with normal prenatal diagnosis result, structural abnormalities were found in four fetuses (4.0%, 4/100) in DCT and two fetuses (2.9%, 2/70) in MCT ( 0.999). There were one intrauterine fetal demises (IUFD) and two miscarry in DCT. One IUFD, three subsequently developed Twin-to-Twin Transfusion Syndrome (TTTS) and four developed selective intrauterine growth restriction (sIUGR) in MCT. Totally, the overall fetal survival rate was 85.1% (97/114) in DCT and 80.6% (58/72) in MCT (χ = 0.653,  = 0.419).

CONCLUSION

Compared to MCT, the incidence of chromosomal abnormalities in DCT discordant for one fetus with NT above the 95th percentile was higher. The risk of structural abnormalities and the rate of fetal survival for both MCT and DCT was similar.