Final answer:
The quadruple screening includes Alpha-fetoprotein (AFP), Estriol (E3), Human chorionic gonadotropin (hCG), and Inhibin A, and is used to assess the risk of a fetus having Trisomy 21 (Down syndrome), which involves an extra copy of chromosome 21. (option a)
Step-by-step explanation:
The marker commonly included in maternal quadruple screening for Trisomy 21 (Down syndrome) is: A) Alpha-fetoprotein (AFP), B) Estriol (E3), C) Human chorionic gonadotropin (hCG), and D) Inhibin A. All these biomarkers are measured in the quadruple screening to assess the risk of a fetus having Trisomy 21. The screening typically occurs in the second trimester of pregnancy and is used along with maternal age to calculate the risk.
Down syndrome is characterized by an extra copy of chromosome 21, which can be seen in a karyotype where there are three copies of this chromosome instead of the usual two. The risk of having a fetus with Down syndrome increases with maternal age, which is why the screening can be particularly important for older pregnant women.
Hence, the answer is option a