Causes of Down syndrome are

Correct Answer: D

Rationale: The correct answer is D because Down syndrome is primarily caused by trisomy of chromosome 21. This means there is an extra copy of chromosome 21, leading to the characteristic features of the syndrome. Mosaicism and translocation of chromosome 21 can also result in Down syndrome, albeit less frequently. Option A includes deletion, which is not a common cause of Down syndrome. Option B lists duplication, which is not a typical mechanism for Down syndrome. Option C includes deletion and mosaicism, but trisomy is the main cause of Down syndrome, making option D the most accurate choice.

Correct Answer: D

Rationale: The correct answer is D because both statements A and C are true. Older mothers have a higher risk of developing preeclampsia due to age-related complications. Additionally, advanced maternal age is associated with an increased likelihood of requiring a cesarean section due to factors like decreased uterine elasticity. Statement B is incorrect as younger mothers are not at higher risk of miscarriage compared to older mothers. This is because maternal age is not a significant factor in miscarriage risk.

Correct Answer: A

Rationale: The correct answer is A: Uterine rupture. This is the most significant risk associated with VBAC, where the scar from the previous cesarean section may tear during labor. This can lead to severe complications for both the mother and baby. Postpartum hemorrhage (B) and placenta previa (C) are potential risks in any pregnancy but are not specifically increased in VBAC. Therefore, the correct answer is A, as it directly relates to the unique risk of VBAC.

Correct Answer: B

Rationale: The correct answer is B: Assess fetal lung maturity. Amniotic fluid analysis measures the levels of substances like surfactant, which indicates lung maturity. This helps in determining if the fetus is ready for delivery. Other choices are incorrect because amniotic fluid analysis is not primarily used to detect fetal infections (A), determine fetal position (C), or assess placental health (D). These functions are typically achieved through other diagnostic tests or imaging techniques.

Correct Answer: D

Rationale: The correct answer is D because the placenta performs multiple functions in managing fetal waste products. It filters toxins, facilitates nutrient absorption, and removes carbon dioxide. The placenta acts as a barrier between the mother and the fetus, allowing for the exchange of nutrients and waste products. Therefore, all of the above choices are correct in describing the role of the placenta in managing fetal waste products. The other choices are incorrect because they do not encompass all the functions that the placenta serves in this context.