The two studies provide information on how to consider use of non-invasive prenatal testing (NIPT) with cell-free DNA (cfDNA) in identical (monozygotic) and fraternal (dizygotic) twin pregnancies.

Previous studies in singleton pregnancies demonstrated the accuracy of the Harmony test in assessing the risk of fetal trisomy 21, which causes Down syndrome, and other chromosome conditions.

Entitled ‘Fetal Fraction Estimate in Twin Pregnancies Using Directed Cell-Free DNA Analysis,’ the first study highlights the importance of estimating the percentage of fetal fraction (FF) in analyzing twin pregnancies with NIPT.

Using NIPT in twin pregnancies is more complex than in singleton pregnancies because the two fetuses can be either monozygotic, meaning both fetuses are genetically identical, or dizygotic, in which case only one fetus is likely to have a trisomy when present. The study concluded that with the Harmony test algorithm, use of the fetal fraction in the analysis of FF for one of the twins will allow for more accurate testing.

The second study, entitled "Cell-free DNA Analysis for Trisomy Risk Assessment in First-Trimester Twin Pregnancies," was conducted by Professor Kypros Nicolaides from the Harris Birthright Research Centre of Fetal Medicine in London.

Among 192 total twin pregnancies as part of a blinded study, the Harmony test correctly classified 9 of 10 pregnancies with fetal trisomy 21, 1 of 1 pregnancies with fetal trisomy 13, and no false positives. Actual clinical implementation of Harmony in twin pregnancies identified 2 trisomy 21 and 1 trisomy 18 affected pregnancies, as well.

Ariosa Diagnostics chief medical officer Dr Thomas Musci noted the company continues its commitment to the publication of peer-reviewed clinical studies demonstrating the value of the Harmony test for trisomy risk assessment.

"Our innovative technology offers an accurate and safe screening option to physicians caring for patients with twins," Dr Musci added.

The Harmony test is a blood test for pregnant women that can be used as early as 10 weeks in pregnancy. By evaluating cfDNA from the fetus found in maternal circulation, the test can assess the risk of Down syndrome with greater than 99% accuracy and provide fetal sex information.

Compared to current prenatal screening tests that have up to a 20% error rate, the Harmony test with its much higher accuracy, represents a significant advance in prenatal testing.