This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: New born infants, Subject name: Pediatrics
Antenatal screening test done in the maternal serum is _______ 
Select and explain. 
A. Percutaneous unbilical blood sampling, B. Cell-free fetal DNA testing, C. Chorionic villus sampling, D. Amniocentesis
B: Cell-free fetal DNA testing
Answer: B: Cell-free fetal DNA testing 
Explanation: Antenatal screening test done in the maternal serum is cell-free fetal DNA testing, which is a non-invasive prenatal screening. This test is done using the freely circulating fetal cells in the maternal serum. It is useful for karyotyping and for detecting single gene disorders. Invasive procedures for prenatal diagnosis Chorionic villous sampling (CVS) Amniocentesis Cordocentesis or percutaneous umbilical blood sampling (PUBS) Ref: Nelson textbook of pediatrics 21st edition Pgno: 969