Double Marker Test- First Trimester

The Double Marker Test- First Trimester measures two biomarkers in maternal blood associated with chromosomal abnormalities.

a) Free beta-hCG (human chorionic gonadotropin): a hormone made by the placenta shortly after a woman becomes pregnant.

b) PAPP-A (pregnancy-associated plasma protein-A): a protein made by the placenta during early pregnancy. It helps the placenta grow and function properly.

These, along with the USG marker and nuchal translucency (NT) measurement, are effective in Combined screening for Down syndrome and trisomy 13/18 in the fetus. This test only gives the risk for the presence of these chromosomal abnormalities in the developing fetus. A positive screen is not diagnostic but indicates that further evaluation should be considered.

hCG is synthesized by the placenta very early in pregnancy and can be detected in the blood 8-11 days after conception. Higher levels of hCG after 11 weeks of gestation may suggest a higher chance of the baby having Down syndrome. On the other hand, low levels indicate an increased risk for trisomy 18.

PAPP-A is a protein produced by the placenta that is needed for the implantation and maintenance of a healthy placenta (afterbirth). Low levels of PAPP-A before the 14th week of pregnancy suggest an increased risk of fetal chromosomal abnormalities.