Double Marker, Serum

The first trimester screening is a combination of tests for PAPP-A (Pregnancy-associated plasma protein-A ), hcg (Human chorionic gonadotropin) and nuchal translucency that are used to assess the risk that the fetus, a pregnant woman is carrying has a chromosome disorder such as Down syndrome (trisomy 21) or Edwards syndrome (trisomy 18) etc. It is performed between 11weeks and 13weeks 6days of pregnancy. Beta-hCG is a hormone synthesized by cells of the placenta. Measurement of hCG assists in diagnosing and dating pregnancy, identifying ectopic pregnancies and other abnormalities, managing certain neoplasms and predicting the risk of Down's syndrome and trisomy 18. Pregnancy-Associated Plasma Protein A is a glycoprotein. Low concentrations of PAPP-A early in pregnancy have been associated with Down's syndrome, IUGR, hypertension and pre-eclampsia, etc. The results help in the early detection of chromosomal anomalies and further management if reqiured. However, the double marker test does not assess risk of neural tube defects such as spina bifida, which can be assessed in the second trimester (triple or quadruple marker tets).

1. What is Down syndrome?

Down syndrome (trisomy 21) causes mental retardation and developmental problems and can be associated with congenital heart defects, respiratory and hearing problems, leukemia, and thyroid disorders. Down syndrome and other chromosomal abnormalities increase with the increased age of the mother.

2. What is Edwards syndrome?

Edwards syndrome (trisomy 18) is associated with multiple fetal abnormalities and is usually fatal. The frequency of this abnormality is much less than Down syndrome, and as with Down syndrome, its risk increases with the increasing maternal age.

3. I am pregnant will I have both first and second trimester screening performed?

Yes, first trimester screening for chromosome abnormalities includes tests for PAPP-A, hCG and nuchal translucency ultrasound. Second trimester maternal serum screening (triple or quad screen) includes tests for inhibin A and AFP additionally.