Correct Answer: D

Rationale: The correct answer is D, isotretinoin. Isotretinoin is a medication commonly used to treat severe acne, but it is a potent teratogen, meaning it can cause severe birth defects if taken during pregnancy. Aspirin (choice A) is not a widely used potent teratogen. Diethylstilbestrol (DES) (choice B) was a known teratogen, but it is not currently widely used. Thalidomide (choice C) was another historical teratogen, but it is also not currently widely used. Therefore, isotretinoin is the most relevant answer as it is a commonly used medication that poses a high risk of birth defects if used during pregnancy.

Correct Answer: B

Rationale: Brain weight increases tenfold from the twentieth week until birth. This rapid growth and development of the brain during the prenatal period is crucial for setting the foundation for future cognitive and neurological functions. Choices A, C, and D are incorrect because although they also undergo changes during prenatal development, none of them increase tenfold from the twentieth week until birth, unlike brain weight.

Correct Answer: D

Rationale: The correct answer is D, isotretinoin. Isotretinoin is a medication commonly used to treat severe acne, but it is a potent teratogen, meaning it can cause severe birth defects if taken during pregnancy. Aspirin (choice A) is not a widely used potent teratogen. Diethylstilbestrol (DES) (choice B) was a known teratogen, but it is not currently widely used. Thalidomide (choice C) was another historical teratogen, but it is also not currently widely used. Therefore, isotretinoin is the most relevant answer as it is a commonly used medication that poses a high risk of birth defects if used during pregnancy.

Correct Answer: C

Rationale: The germinal period lasts about two weeks and occurs during the first two weeks of pregnancy. This is the time when the fertilized egg implants into the uterus and begins to divide rapidly. It is followed by the embryonic period, which lasts from about week 3 to week 8 of pregnancy. Choice A is incorrect because the germinal period happens in the early stages of pregnancy, not the second trimester. Choice B is incorrect because the germinal period typically lasts about two weeks, not six. Choice D is incorrect because the germinal period is an early stage of pregnancy and not the final period of a 38-week pregnancy.

Correct Answer: A

Rationale: Impaired brain functioning is a major contributor to Sudden Infant Death Syndrome (SIDS). Research has shown that abnormalities in the brainstem, which controls automatic functions like breathing and heart rate, can play a role in SIDS cases. As such, mounting evidence suggests that compromised brain functioning is a significant factor in the occurrence of SIDS. Choices B, C, and D are incorrect. Higher-than-average birth weight, organized and patterned sleep behavior, and a family history of chromosomal abnormalities are not identified as major contributors to SIDS according to the provided information.