The harm done by teratogens __________.

Correct Answer: D

Rationale: The harm done by teratogens depends on the age at the time of exposure. This means that the effects may vary depending on the developmental stage of the fetus when exposed to the teratogen. Teratogens can have different impacts at different stages of pregnancy, leading to a range of potential outcomes in terms of physical and/or cognitive development. Choices A, B, and C are incorrect because the harm caused by teratogens is not straightforward, may not be apparent at birth, and can go beyond physical damage, affecting cognitive development as well.

Correct Answer: B

Rationale: Passive smoking, also known as secondhand smoke, can have harmful effects on pregnancies. Research has shown that exposure to smoke-filled environments during pregnancy is linked to low birth weight, infant death, and childhood respiratory illnesses. Pregnant women should avoid exposure to secondhand smoke to protect the health of their unborn babies. Choice A is incorrect because passive smoking affects both the mother and the unborn child, not just children born to heavy smokers. Choice C is incorrect as it underestimates the risks of smoke-filled environments on unborn children. Choice D is incorrect as research has already established the harmful effects of passive smoking on pregnancies.

Correct Answer: B

Rationale: Low-level radiation, whether from industrial leakage or medical X-rays, can increase the risk of childhood cancer by potentially damaging the developing fetus's cells. Even though the risk is relatively low, it is still a significant concern that should be acknowledged and monitored closely, especially during prenatal development. Choice A is incorrect as low-level radiation can still be harmful on its own without the need to be combined with other teratogens. Choice C is incorrect because low-level radiation exposure can indeed cause lasting damage, especially in the context of childhood cancer risk. Choice D is incorrect because low-level radiation exposure, even during the last trimester, can pose risks to the developing fetus and is not considered entirely safe.

Correct Answer: B

Rationale: The correct answer is B: 'In South Africa, 30 percent of all pregnant women are HIV-positive.' This statement is true as South Africa has a high prevalence of HIV among pregnant women, emphasizing the need for interventions to prevent mother-to-child transmission. Choices A, C, and D are incorrect. Choice A is inaccurate as women account for more than 50% of new HIV infections globally. Choice C is misleading as the majority of new HIV infections actually occur in sub-Saharan Africa, not just developing countries. Choice D is also incorrect as without treatment, the risk of mother-to-child transmission is higher than 30%.

Correct Answer: C

Rationale: Prenatally malnourished babies frequently catch respiratory illnesses. Malnourished babies have weakened immune systems, making them more susceptible to illnesses such as respiratory infections. This is a common consequence that is observed in babies who did not receive adequate nutrition during the prenatal period. Choices A, B, and D are incorrect. While malnourished babies may have feeding challenges, rejecting breast milk is not a common consequence. Enlarged hearts are not typically associated with prenatal malnutrition, and having a higher-than-average birth weight is unlikely in malnourished babies.