Cell-free DNA screening for trisomy 21 in twin pregnancy: a large multicenter cohort study

First-Trimester Ultrasound Screening in Routine Obstetric Practice

“…In October 2011, cell-free DNA screening for the common autosomal trisomies was introduced into clinical care, with markedly improved test performance metrics in both singleton and twin gestations. 31–33 Nationally, the rapid adoption of cell-free DNA screening for aneuploidy has led to a decline in the use of screening paradigms that require a precise measurement of the nuchal translucency and a decrease in the number of patients receiving first-trimester ultrasound examinations. 34,35…”

“…30 In October 2011, cell-free DNA screening for the common autosomal trisomies was introduced into clinical care, with markedly improved test performance metrics in both singleton and twin gestations. [31][32][33] Nationally, the rapid adoption of cell-free DNA screening for aneuploidy has led to a decline in the use of screening paradigms that require a precise measurement of the nuchal translucency and a decrease in the number of patients receiving firsttrimester ultrasound examinations. 34,35 Ultrasound examination before cell-free DNA has been shown to be cost effective, and societal guidelines in the United States have suggested that obstetric ultrasound examination may be useful before cell-free DNA screening.…”

Prenatal Genetic Screening in Twin Pregnancy

“…This lack of data resulted in wide confidence intervals when attempting to calculate detection rates for T13 and T18 15 . A recent multicenter retrospective cohort study of 1764 twin pregnancies from 17 US centers including 42 pregnancies with T21 reported a 97.6% (95% CI 83.8-99.7) detection rate 16 . The median gestational age at cfDNA screening was 12.3 weeks.…”

“…When retesting is performed for a no-call result dichorionic twin pregnancies are also more likely than singletons to have a second no-call result (45.1% chance of a second no-call result for dichorionic twins versus 32.7% chance for singletons) 17 . It is likely that the non-reportable rates for cfDNA screening twins will decrease with advances technology as evidenced by the 2023 multicenter US study of 1764 twin pregnancies in which 3.9% of twin pregnancies had a non-reportable result, with 58% of cases with second draw receiving a result 16 . There are several risk factors for non-reportable results that may be more common in twin pregnancies including conception with in vitro fertilization, advanced maternal age, and abnormal placentation 17 …”