Unit 2: Prenatal Development and Infancy

Answer: B — The correct answer is B because the formation of the placenta and umbilical cord is crucial during the first trimester as it provides the fetus with the necessary oxygen and nutrients for growth and development. Option A is incorrect because while a healthy diet and exercise routine are important for the mother's overall health, they are not the most critical factors at this specific stage. Option C is incorrect because the mother's emotional state and stress levels, although important, do not directly impact fetal development as much as the placenta and umbilical cord. Option D is incorrect because while the father's genetic contribution is important, it is not the most critical factor during the first trimester.

Answer: C — The correct answer is C because elevated levels of alpha-fetoprotein (AFP) in a fetus's bloodstream are often associated with open neural tube defects, such as spina bifida. This is because AFP is a protein that is normally produced by the fetus's liver and yolk sac, but when there is an open neural tube defect, AFP can leak into the amniotic fluid and then into the mother's bloodstream, resulting in elevated levels. Options A, B, and D are incorrect because while some prenatal screening tests can detect genetic disorders like Down syndrome, elevated AFP levels are more specifically associated with open neural tube defects. Option B is partially correct but does not provide the most likely explanation for the elevated AFP levels.

Answer: D — Folic acid is crucial during the prenatal period because it helps to prevent neural tube defects, which are birth defects of the brain and spine. While folic acid does have other benefits, such as supporting the development of the baby's nervous system, its primary role is in preventing neural tube defects. Options A, B, and C are incorrect because while folic acid may have some secondary benefits, they are not the primary reason why it is crucial during the prenatal period.

Answer: B — Folic acid supplementation is recommended for all pregnant women to prevent neural tube defects, which are birth defects of the brain and spine. The other options are incorrect because folic acid supplementation is necessary for all pregnant women, regardless of family history, and it should be started before conception or early in pregnancy, not after the first trimester. Additionally, a daily multivitamin may not contain enough folic acid to support fetal development.

Answer: D — Folic acid is crucial for preventing neural tube defects, which are birth defects of the brain and spine. A deficiency in folic acid can lead to an increased risk of neural tube defects. The other options are not directly related to folic acid deficiency. Morning sickness can contribute to other complications, but the specific concern with folic acid deficiency is neural tube defects.