Limb defects (flipper limbs) are associated with which teratogen?

Limb defects (flipper limbs) are associated with which teratogen?

• A. Isotretinoin
• B. Thalidomide
• C. Methimazole
• D. Lithium

Answer: (B)

Limb formation happens early in pregnancy, and certain drugs taken during that window can disrupt limb bud development. Thalidomide, when exposure occurs in the first trimester, can interrupt this process and lead to phocomelia, where the limbs are abnormally short or “flipper-like.” This pattern is the classic association, making thalidomide the best answer. Other agents listed tend to cause different defect patterns: isotretinoin commonly causes craniofacial and organ system abnormalities; methimazole can lead to scalp defects like aplasia cutis; lithium is associated with Ebstein anomaly of the tricuspid valve.

Limb formation happens early in pregnancy, and certain drugs taken during that window can disrupt limb bud development. Thalidomide, when exposure occurs in the first trimester, can interrupt this process and lead to phocomelia, where the limbs are abnormally short or “flipper-like.” This pattern is the classic association, making thalidomide the best answer.

Other agents listed tend to cause different defect patterns: isotretinoin commonly causes craniofacial and organ system abnormalities; methimazole can lead to scalp defects like aplasia cutis; lithium is associated with Ebstein anomaly of the tricuspid valve.