Teratogens and Organogenesis

The correct answer is B.

Explanation:

Embryonic tissue is most susceptible to teratogens during the 3rd through 9th weeks of pregnancy. This is when organogenesis occurs, and when most major congenital anomalies occur. But since brain development occurs throughout pregnancy, it is wisest for a pregnant woman to avoid alcohol for all 9 months of gestation.

The first 2 weeks (choice A) of pregnancy are not generally associated with teratogenicity, unless so many of the cells of the conceptus are irreversibly damaged that death results. Otherwise, the abundance of undifferentiated cells present are able to compensate for the damage.

The 9th through 12th weeks (choice C) are associated with minor congenital anomalies, including those of the eyes, palate, teeth, and ears.

The 12th through 16th weeks (choice D) and 16th through 20th weeks (choice E) are associated with minor congenital anomalies, including those of the eyes, teeth, ears, and external genitalia. Minor CNS anomalies may initiate during the 20th week.

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