Final answer:
Pregnancy safety category D is used for medications with evidence of human fetal risk, where benefits may outweigh risks. Factors including the drug's mutagenic potency, the teratogen dose, and fetal susceptibility are considered. Illicit substances, alcohol, and drugs like thalidomide are known teratogens with serious effects.
Step-by-step explanation:
A medication that poses a possible risk to the fetus falls under pregnancy safety category D if there is positive evidence of human fetal risk, but the potential benefits from the use of the drug in pregnant women may be acceptable despite its potential risks. This assessment is based on factors such as the potency of the drug as a mutagen, the dose of the teratogen, and the susceptibility of the fetus to teratogenesis. It is important to weigh the risks and benefits when determining whether a drug is suitable for use in pregnancy. Teratogens like alcohol cause severe risks like fetal alcohol spectrum disorders (FASD), while others such as thalidomide have been known to cause limb defects. The use of illicit substances like heroin, cocaine, and methamphetamine during pregnancy can lead to severe consequences, including addiction and withdrawal symptoms in newborns that require medically supervised weaning.