North American Registry of Midwives (NARM) Practice Exam

At what point in pregnancy should the maternal serum alphafetoprotein (AFP) of the triple screen be performed?

1. 11 to 14 weeks gestational age

2. 15 to 18 weeks gestational age

3. 19 to 22 weeks gestational age

4. 23 to 26 weeks gestational age

The correct answer is: 15 to 18 weeks gestational age

The maternal serum alpha-fetoprotein (AFP) test, which is part of the triple screen, is typically performed during the gestational age range of 15 to 18 weeks. This timing is crucial because it allows for optimal detection of potential abnormalities, such as neural tube defects and chromosomal conditions like Down syndrome, that can be indicated by abnormal levels of AFP in the mother's blood. At this stage of pregnancy, the levels of AFP are sufficiently elevated as the fetus is growing, and the placenta is actively producing the protein. If the test is performed too early, such as during the first trimester (11 to 14 weeks), the AFP levels may not be representative of what is expected at later stages, possibly leading to inaccurate results. If it is done too late in the pregnancy, the window for considering follow-up diagnostic testing or interventions can close, limiting the options available for managing any identified risks. Therefore, the correct timing for the AFP test in the context of the triple screen is between 15 to 18 weeks of gestation, facilitating effective screening and appropriate clinical response when necessary.