Sidney Q. Cohlan studied birth defects in the US during the twentieth century. Cohlan helped to discover that if a pregnant woman ate too much vitamin A her fetus faced a higher than normal risk of teratogenic effects, such as cleft palate. A teratogen is a substance that causes malformation of a developing organism. Cohlan also identified the teratogenic effects of several other substances including a lack of normal magnesium and prenatal exposure to the antibiotic tetracycline. Cohlan's experiments with vitamins and other chemicals brought attention to how nutrition and environmental agents adversely affect human pregnancy outcomes.

Gonorrhea is a sexually transmitted disease, or STD, caused by the bacterium Neisseria gonorrhoeae. Common symptoms of the disease include painful urination and genital discharge. There are records of historical discussions of gonorrhea in ancient civilizations and during the Middle Ages, but scientists did not begin investigating the scientific causes and treatments of the STD until the sixteenth century. In the 1700s, physicians attributed gonorrhea to the same cause as another STD, syphilis. Later, in the 1800s, researchers discovered the two diseases were not the same and identified the bacteria N. gonorrhoeae that causes gonorrhea. By the 1900s, researchers began using antibiotics to target the bacteria, but many drugs eventually developed antibiotic resistance. In 2020, the World Health Organization, or WHO, estimated that 82.4 million individuals contracted gonorrhea globally, and as of 2024, researchers continue to experiment with various antibiotic drugs to provide adequate treatment for the disease.