Advances in molecular technologies have resulted in the introduction of next-generation sequencing of maternal plasma DNA for prenatal identification of Down syndrome and other common trisomies. 1,2 Circulating cell-free (ccf) DNA of placental/fetal origin 3 in the maternal circulation is thought to be released by apoptotic cells of the placenta, 4 and the success of next-generation sequencing is dependent on the percentage of fetal (placental) DNA present in maternal plasma (the fetal fraction). The higher the fetal fraction, the more easily a trisomy or other aneuploidy can be detected. On average, 13% of ccf DNA in maternal plasma is of fetal (placental) origin, and fetal fractions of less than 4% may not be sufficient for reliable testing. 1 First and second trimester maternal serum marker levels are known to be altered in pregnancies conceived using assisted reproductive technologies (ART) versus those conceived naturally (controls). [5][6][7][8][9][10] In particular, secretory products of the placenta, such as human chorionic gonadotropin and inhibin A, are 10-30% higher in pregnancies from ART relative to control pregnancies. The cause of the increased secretion is not known. Regardless, serum marker levels can be adjusted so that screening performance in ART pregnancies is comparable with that of controls. Given that a portion of ccf DNA also is released by placental cells, albeit by a different mechanism, we sought to explore the possibility that the levels of ccf DNA also differed between ART and control pregnancies. If ART pregnancies were to release at least as much fetal-specific ccf DNA into maternal blood as do naturally conceived pregnancies, this could reassure clinicians that next-generation testing in ART pregnancies would perform at least as well as in naturally conceived pregnancies. In addition, we examined the chromosome-specific z-score and the final interpretation of the testing in the ART and control pregnancies.
MATERIALS AND METHODSSamples for this study were selected from among those reported earlier as part of a multicenter international clinical validation of a next-generation sequencing test for Down syndrome. 1Purpose: We sought to compare measurements of circulating cellfree DNA as well as Down syndrome test results in women with naturally conceived pregnancies with those conceived using assisted reproductive technologies.Methods: Data regarding assisted reproductive technologies were readily available from seven enrollment sites participating in an external clinical validation trial of nested case/control design. Measurements of circulating cell-free fetal and total DNA, fetal fraction (ratio of fetal to total DNA), chromosome-specific z-scores, and karyotype results were available for analysis.Results: Analyses were restricted to 632 euploid (5.2% assisted reproductive technologies) and 73 Down syndrome (13.7% assisted reproductive technologies), including 16 twin pregnancies. No differences were found for fetal or total circulating cell-free DNA, or for the fetal fraction in ...