Which of the following is a marker for Down's Syndrome?

Ans. is 'b' i.e., Decresed maternal serum alpha feto protein Antenatal Screening for Downs syndromeo Following methods are used :-1) Triple test: It includesi) Unconjugated estrogen (estriol): decreased;ii) Maternal serum alpha- feto protein (MSAFP): decreased; andiii) hCG: increased(Note: All these three markers are decreased in Edward syndrome)2) New markers: These are (i) Increased inhibin A in maternal blood; and (ii) Decreased PAPA (pregnancy associated plasma protein).3) USG: It shows: (i) Increased nuchal translucency (increased nuchal fold thickness) in first trimester; (ii) Ductus venous flow reversed; and (iii) Nasal bone hypoplasia.4) Karyotyping: It can be done by chorionic villus sampling at 10-12 weeks or aminocentesis at 16-18 weeks.