Marker

Standard Deviation

Alpha-fetoprotein/hCG

0.05 to 0.30

Alpha-fetoprotein/Beta hCG free in 2nd trimester

0.01 to 0.2

Alpha-fetoprotein/uE3

0.09 to 0.3

hCG/uE3

−0.01 to −0.15

PAPP-A/Beta hCG free 1^st trimester

0.05 to 0.25