A major aortopulmonary collateral artery is a rare and easily missed diagnosis that is usually associated with Tetralogy of Fallot or pulmonary atresia. We present two cases of major aortopulmonary collaterals associated with trisomy 21 and atrioventricular septal defect with balanced ventricles in which the diagnosis went undetected until after initial cardiac repair.

Massively parallel sequencing (MPS) technology has become increasingly availableand has been widely used to screen for trisomies 21, 18, and 13 in singletonpregnancies. This study assessed the performance of MPS testing of cell-freefetal DNA (cffDNA) from maternal plasma for trisomies 21, 18, and 13 in twinpregnancies. Ninety-two women with twin pregnancies were recruited. The resultswere identified through karyotypes of amniocentesis or clinical examination andfollow-up of the neonates. Fluorescent in-situ hybridization was used to examinethe placentas postnatally in cases of false-positive results. The fetuses withautosomal trisomy 21 (n = 2) and trisomy 15 (n= 1) were successfully detected via MPS testing of cffDNA. There was onefalse-positive for trisomy 13 (n = 1), and fluorescence in-situhybridization (FISH) identified confined placental mosaicism in this case. Fortwin pregnancies undergoing second-trimester screening for trisomy, MPS testingof cffDNA is feasible and can enhance the diagnostic spectrum of non-invasiveprenatal testing, which could effectively reduce invasive prenatal diagnosticmethods. In addition to screening for trisomy 21, 18, and 13 by cffDNA, MPS candetect fetal additional autosomal trisomy. False-positive results cannotcompletely exclude confined placental mosaicism.