To assess the clinical value of nuchal translucency (NT) thickening, NT discordance, and crown-rump length (CRL) discordance in screening twins with different degrees of congenital heart malformation at 11-13⁺⁶ weeks of pregnancy.

A retrospective analysis was performed on twin fetal cases collected from Beijing Obstetrics and Gynecology Hospital Capital Medical University/Beijing Maternal and Child Health Care Hospital (January 2012 to December 2016) and the Fourth Hospital of Shijiazhuang City (January 2014 to December 2018). Fetuses with cardiac malformation were screened out and divided into either a mild cardiac malformation group or a complex cardiac malformation group according to the degree of cardiac malformation, and normal twins delivered at the same time were used as controls. The NT value of all enrolled cases at 11-13⁺⁶ weeks of gestation was obtained, and the number of cases with NT value ≥ the 95th percentile, NT value ≥ the 99th percentile, NT discordance ≥ 20%, and CRL discordance ≥ 10% was recorded. The χ² test or Fisher's exact probability method was used for comparative analysis between groups, and Logistic regression analysis was used to screen the risk factors for cardiac malformations in twins.

There were 23 cases of twins with cardiac malformation, including 14 cases in the mild cardiac malformation group, 9 cases in the complex cardiac malformation group, and 1906 cases in the normal control group. Compared with the control group, the incidence of NT value ≥ the 95^th percentile, NT value ≥ the 99^th percentile, and CRL discordance ≥ 10% in the complex cardiac malformation group was significantly higher (χ²=63.628, 53.480, and 8.064; P<0.001, <0.001, and =0.020, respectively), while the incidence of NT discordance ≥ 20% was not statistically different between the complex cardiac malformation group and the control group. There was no statistically significant difference in various indicators between the mild cardiac malformation group and the control group. Except for the NT value ≥ the 95th percentage (χ²=4.480, P=0.014), there was no significant difference in other indicators between the mild cardiac malformation group and the complex cardiac malformation group. Multivariate Logistic regression analysis showed that increased NT (NT value ≥ the 95^th percentile) was an independent risk factor for the occurrence of complex cardiac malformations in twins (odds ratio=31.571, 95% confidence interval: 8.022-124.246, P<0.001), but CRL discordance ≥ 10% was not an independent risk factor for complex cardiac malformation in twins (P>0.05).

Ultrasound at 11-13⁺⁶ weeks of gestation reveals NT increase in one or two fetuses of the twins, and CRL discordance ≥ 10% indicates an increased risk of complex cardiac malformations in twins. Increased NT is a risk factor for complex heart malformations in twins.