Which statement defines a critical period in prenatal development?

Which statement defines a critical period in prenatal development?

• A. A time when exposure to teratogens can cause the most harm; organogenesis weeks 3-8
• B. There is no specific period of heightened sensitivity
• C. Teratogens affect development only postnatally
• D. Critical periods happen only in psychology, not biology

Answer: (A)

Critical periods are windows when development is especially sensitive to environmental influences because key processes are actively occurring. In prenatal development, organ formation—organogenesis—happens roughly during weeks 3 to 8, so exposure to teratogens then can cause the most severe and often irreversible abnormalities. Outside this period, the same exposure might have different or milder effects, since the major formation of organs has passed. The idea that there isn’t a specific sensitive window or that effects only happen after birth isn’t aligned with how development unfolds biologically. This statement correctly identifies a time of greatest vulnerability due to active organ formation.

Critical periods are windows when development is especially sensitive to environmental influences because key processes are actively occurring. In prenatal development, organ formation—organogenesis—happens roughly during weeks 3 to 8, so exposure to teratogens then can cause the most severe and often irreversible abnormalities. Outside this period, the same exposure might have different or milder effects, since the major formation of organs has passed. The idea that there isn’t a specific sensitive window or that effects only happen after birth isn’t aligned with how development unfolds biologically. This statement correctly identifies a time of greatest vulnerability due to active organ formation.