Cell-free DNA screening effective for detecting trisomy 21 in twins

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In a recent study, cell-free DNA screening had high rates of detecting trisomy 21 in twin gestations.

Cell-free DNA screening effective for detecting trisomy 21 in twins | Image Credit: © Martin Valigursky - © Martin Valigursky - stock.adobe.com.

Cell-free DNA screening effective for detecting trisomy 21 in twins | Image Credit: © Martin Valigursky - © Martin Valigursky - stock.adobe.com.

Cell-free DNA (cfDNA) is effective in first-trimester screening for trisomy 21 among twin gestations, according to a recent study published in the American Journal of Obstetrics & Gynecology.

Takeaways

  • Cell-free DNA (cfDNA) screening is effective in detecting trisomy 21 in twin pregnancies during the first trimester.
  • Challenges exist when using cfDNA screening for twin gestations, including low aneuploidy rates and technical difficulties.
  • Data on cfDNA screening in twin pregnancies is limited, and few cases have been affected according to the American College of Obstetricians and Gynecologists.
  • A retrospective cohort study involving 1,447 cases found that cfDNA screening in twin pregnancies had a sensitivity of at least 90%, with most cases being dichorionic.
  • Future research should focus on factors that affect fetal fraction and the incidence of nonreportable results in twin gestation cfDNA screening.

Efficacy has been shown when screening cfDNA from maternal blood to determine trisomy 21 in singleton pregnancies. However, there are challenges in screening twin gestations using this method. These challenges include low aneuploidy rates in twins making it difficult to perform a proper prospective trial and technical challenges associated with cfDNA screening in twin gestations.

Currently, data on cfDNA screening in twin gestations is limited. The American College of Obstetricians and Gynecologists has stated cfDNA screening can be performed in twin gestations, but few cases have been affected.

To determine the efficacy of cfDNA screening for trisomy 21 among twin gestations, investigators conducted an investigator-initiated, retrospective cohort study. Data on cfDNA screenings between December 2011 and February 2020 was obtained from 17 centers.

Exclusion criteria included having a known vanishing twin, lacking follow-up data, and screening for a second twin pregnancy in the same patient. All cases sent for twin cfDNA analysis without these conditions were included.

Data obtained included genetic study results, placental pathology results, ultrasound reports, autopsy reports, maternal demographic characteristics, pregnancy outcome data, and newborn follow-up data. The primary study investigator reviewed all cases. A sensitivity of at least 90% was determined by 35 or more confirmed twin pregnancies with 1 or more twin affected by trisomy 21.

There were 1447 cases included in the final analysis. Participants had a median maternal age of 35 years and body mass index of 25.1 kg/m2. Only 11% of pregnant patients receiving cfDNA screening were Black and another 11% were Asian. Of twin pregnancies, 81% were dichorionic and 42% were conceived through in vitro fertilization.

Trisomy 21 was reported in 42 pregnancies, with 41 cases being true positive results and 1 being false negative. Thirty-eight of the 41 true positive cases were dichorionic. Of samples collected, 3.9% were nonreportable for the first sample, and 58.5% of these were reportable for the second sample.

These results indicated efficacy from first trimester cfDNA screening in determining trisomy 21 in twin gestations. Investigators recommended future studies target, “factors that influence the fetal fraction and the incidence of nonreportable results.”

Reference

Dugoff L, Koelper NC, Chasen ST. Cell-free DNA screening for trisomy 21 in twin pregnancy: a large multicenter cohort study. American Journal of Obstetrics & Gynecology. 2023;229(4).doi:10.1016/j.ajog.2023.04.002

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