Isotretinoin is a molecule and a byproduct (metabolite) of vitamin A, and in greater than normal amounts in pregnant women, it can cause fetal abnormalities including cleft lips, ear and eye defects, and mental retardation. Isotretinoin is commonly called by its trade name Accutane, and it's a chemical compound derived from vitamin A, or retinoic acid. Doctors prescribe isotretinoin to treat severe acne. For pregnant women, too much vitamin A or isotretinoin can also cause greater than normal rates of stillbirths and fetal disintegrations after the ninth week of gestation. Women who use isotretinoin during the first trimester of their pregnancies, even in small amounts, risk defects to their fetuses such as external ear malformations, cleft palates, undersized jaws (micrognathia), a variety of heart defects, buildups of fluids inside the skulls that leads to brain swelling (hydrocephalus), small heads and brains (microcephaly), and mental retardation.

Cocaine use by pregnant women has a variety of effects on the embryo and fetus, ranging from various gastro-intestinal and cardiac defects to tissue death from insufficient blood supply. Thus, cocaine has been termed a teratogen, or an agent that causes defects in fetuses during prenatal development. Cocaine is one of the most commonly used drugs in the US and it has a history of both medical and illegal recreational use. It is a drug capable of a wide array of effects on physical and mental health. Research on the teratogenic effects of cocaine began in the early 1980s, and in 1985 research on the effects of cocaine on prenatal development gained widespread attention. Since then, numerous studies have contributed to information about the detrimental impacts of maternal cocaine use on embryonic and fetal development.

The US Supreme Court case Ferguson v. City of Charleston (2001) established that public hospitals couldn't legally drug test pregnant women without their consent when those women sought prenatal care at those hospitals. The court held that such searches violated the pregnant women's protections under the Fourth Amendment to the US Constitution. The decisions also indicated those circumstances that qualified as special needs exceptions to the Fourth Amendment, and it highlighted the extent to which pregnant women are sovereign individuals in the eyes of the Court. Ferguson v. City of Charleston brought public attention to women's reproductive rights and to fetal rights.

Josef Warkany studied the environmental causes of birth defects in the United States in the twentieth century. Warkany was one of the first researchers to show that factors in the environment could cause birth defects, and he helped to develop guidelines for the field of teratology, the study of birth defects. Prior to Warkany’s work, scientists struggled to explain if or how environmental agents could cause birth defects. Warkany demonstrated that a deficiency or excess of vitamin A in maternal nutrition could cause birth defects. He also established that mercury in teething powders increased infant mortality rates. Warkany showed how substances outside the human body could adversely affect conception, growth, and development of the human fetus in utero.

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.

The article Experimental Studies on Congenital Malformations was published in the Journal of Chronic Diseases in 1959. The author, James G. Wilson, studied embryos and birth defects at the University of Florida Medical School in Gainesville, Florida. In his article, Wilson reviewed experiments on birds and mammals from the previous forty years to provide general principles and guidelines in the study of birth defects and teratogens, which are things that cause birth defects. Those principles included what species are convenient for conducting teratological research, what principles act in human embryological and fetal development, and what agents impact those processes. Wilson's article was one of the first attempts in the twentieth century to synthesize basic research conducted in the field of teratology. The article helped to establish teratology as a field in medicine during the twentieth century.

Thalidomide is a sedative drug introduced to European markets on 1 October 1957 after extensive testing on rodent embryos to ensure its safety. Early laboratory tests in rodent populations showed that pregnant rodents could safely use it, so doctors prescribed Thalidomide to treat morning sickness in pregnant women. However, in humans Thalidomide interfered with embryonic and fetal development in ways not observed in rodent tests. Pregnant women who take Thalidomide are at grater than normal risk for spontaneous abortion and for giving birth to children with developmental anomalies such as shortened, absent, or extra limbs, as well as a variety of heart, ear, and internal organ defects. The failure of rodent models to inform scientists of Thalidomide's teratogenicity in humans ignited debate about the proper use of cross-species testing during drug development.

This project focuses on the history of how teratogens, or agents which have the potential to cause birth defects, have been understood and tested for teratogenic potential in the US over the twentieth century. Prior to this time, teratogen studies were primarily concerned with cataloguing defects rather than exploring possible causes. At the turn of the twentieth century, experimental teratogen studies with the aim of elucidating mechanisms commenced. However, these early studies did not aim to discover human pregnancy outcomes and ways to prevent them, but simply focused on the results of exposing pregnant mammals to various physical and chemical insults.

Thalidomide, a drug capable of causing fetal abnormalities (teratogen), has caused greater than ten thousand birth defects worldwide since its introduction to the market as a pharmaceutical agent. Prior to discovering thalidomide's teratogenic effects in the early 1960s, the US Food and Drug Administration (FDA) did not place regulations on drug approval or monitoring as it later did. By 1962, approximately 20,000 patients in the US had taken thalidomide as part of an unregulated clinical trial before any actions were taken to stop thalidomide's distribution. Due to thalidomide's effects on fetuses, both nationally and abroad, the US Congress passed the 1962 Kefauver-Harris Amendments to the 1938 Food, Drug, and Cosmetic Act. These amendments imposed guidelines for the process of drug approval in the US and required that a drug be safe as well as effective before it could be approved and marketed. Thalidomide also influenced the FDA's creation of pregnancy categories; a ranking of drugs based on their effects on reproduction and pregnancy. Thalidomide motivated the laws on regulating and monitoring drugs developed in the US and by the FDA in the twentieth and twenty-first centuries.

In the case Whitner v. South Carolina in 1997, the South Carolina State Supreme Court defined the concept of a child to include viable fetuses. This allowed grounds for prosecution of a pregnant womanÕs prenatal activity if those activities endangered or could potentially endanger the fetus within her. The case brought the issue of fetal rights versus pregnant womenÕs rights to light. The case also explored whether or not the conviction of a pregnant woman was in the best interest of a fetus, because fear of prosecution could lead the woman to not seek prenatal care or to seek an abortion outside of licensed clinics.