ABT Reproductive and Developmental Toxicology

Question 1

Which period of prenatal development is most sensitive to teratogenic agents causing structural malformations?

Accepted Answer

Weeks 3–8 (organogenesis)

Answer

The embryonic period (weeks 3–8), when organogenesis occurs, is the most sensitive window for structural teratogenesis because organ rudiments are being established.

Question 2

Thalidomide caused phocomelia (limb reduction defects) when taken during which gestational window?

Accepted Answer

Days 27–40

Answer

Thalidomide causes limb reduction defects (phocomelia) when exposure occurs during days 27–40 of gestation, coinciding with limb bud development.

Question 3

The Reproductive and Developmental Toxicant classification system in the US uses which regulatory framework?

Accepted Answer

GHS/OSHA Hazard Communication Standard

Answer

The GHS (Globally Harmonized System) adopted by OSHA's Hazard Communication Standard classifies reproductive and developmental toxicants into Category 1A, 1B, and 2 based on evidence strength.

Question 4

Which drug is a known human teratogen classified FDA Category X and causes fetal hydantoin syndrome?

Accepted Answer

Phenytoin

Answer

Phenytoin causes fetal hydantoin syndrome, characterized by craniofacial abnormalities, digit/nail hypoplasia, and cognitive impairment, and is classified FDA Category X (contraindicated in pregnancy).

Question 5

Which mechanism explains the selective vulnerability of the fetal brain to methylmercury neurotoxicity?

Accepted Answer

Incomplete blood-brain barrier and active neuronal migration in the developing CNS

Answer

The immature blood-brain barrier and ongoing neuronal migration, proliferation, and differentiation during fetal development make the fetal CNS highly vulnerable to methylmercury neurotoxicity.

ABT - American Board of Toxicology Practice Test

ABT - American Board of Toxicology Practice Test

ABT Reproductive and Developmental Toxicology