Published online by Cambridge University Press: 11 October 2022
Screening for aneuploidies should be offered in twin pregnancies, but it is complicated by several factors. While monozygotic twins are genetically identical and one risk estimation is provided for the whole pregnancy, dizygotic twins require a risk estimation for each fetus. Screening by maternal age alone is currently not recommended because of its poor performance; however, screening by fetal nuchal translucency thickness, the first trimester combined test or cell free DNA testing are effective methods of screening which show similar performance in twin pregnancies as compared to singleton pregnancies. The performance of the second trimester quadruple test is much poorer in twin than in singleton pregnancies and therefore its use should be limited to those cases where other methods are not available. For multiple pregnancies of order three or higher, a combination of maternal age and fetal nuchal translucency thickness provides the best performance.
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