Thalidomide is safe to use during pregnancy.

Thalidomide was introduced in the late 1950s as a sedative and was promoted in several countries for nausea during pregnancy. Existing animal tests had not revealed its devastating human teratogenicity.

The pattern became visible clinically. In 1961, physicians independently linked maternal thalidomide use with a striking cluster of severe congenital abnormalities, especially shortened or absent limbs but also defects of the ears, eyes, heart, and internal organs.

Timing mattered enormously. Exposure during a narrow window of early embryonic development could produce major malformations.

The drug was withdrawn in many countries, and the disaster transformed expectations for reproductive toxicology, clinical evidence, and drug regulation.

The United States largely avoided the original catastrophe because FDA reviewer Frances Kelsey refused to approve thalidomide without stronger safety evidence.

Thalidomide itself later returned under tightly controlled conditions for diseases including multiple myeloma and complications of leprosy.

Therapeutic usefulness does not reduce its teratogenicity. Modern treatment requires rigorous pregnancy-prevention systems because even limited exposure during susceptible stages can be catastrophic.