The Malthusian League, founded in London, England, in 1877 promoted the use of contraception to limit family size. Activists Charles Bradlaugh and Annie Besant established the Malthusian League after they were arrested and exonerated for publishing a pamphlet describing techniques to prevent pregnancy. Founders based the league on the principles of Thomas Malthus, a British nineteenth century economist, who wrote on the perils of a population growing beyond the resources available to support it. The Malthusian League advocated for limiting family size voluntarily through contraception to avoid the overpopulation and poverty cautioned in Malthus’ work. After fifty years, the Malthusian League closed due to the increasing disapproval for Malthus’s economic theories of population and poverty. However, the Malthusian League’s activism during the late nineteenth and early twentieth centuries led to more tolerant views of contraception and family planning in Great Britain in the twentieth century.

Roberto Caldeyro-Barcia studied fetal health in Uruguay during the second half of the twentieth century. Caldeyro-Barcia developed Montevideo units, which are used to quantify intrauterine pressure, or the force of contractions during labor. Intrauterine pressure is a useful measure of the progression of labor and the health of a fetus. Caldeyro-Barcia’s research on fetal health often contradicted common obstetric practices, prompting him to publically challenge practices such as induction of labor using oxytocin, forced pushing during labor, and birth position in which the woman lays on her back during labor. Caldeyro-Barcia’s methods of monitoring intrauterine pressure and development of Montevideo units furthered research in maternal and fetal health and improved the use of medical interventions during labor and delivery.

"Casti Connubii," a papal encyclical given by Pope Pius XI on 31 December 1930, served primarily as a reaffirmation and expansion of the issues discussed in Arcanum, an encyclical written by Pope Leo XIII. It was released to address new threats to marriage and conjugal unity, and indeed is translated "On Christian Marriage" or "On Chastity in Marriage." The document explores the meaning of Christian marriage and emphasizes its threefold purpose as borrowed from St. Augustine: to produce offspring, to grow in conjugal faith, and to show benefit from the sacrament. It begins by exploring the nature of marriage, followed by a discussion of its advantages for individuals and societies, erroneous but common beliefs about marriage, threats to pure marriage, and finally how to address them. Included in the threats to pure marriage is that of the growing popularity of contraception and abortive procedures, at which point Pope Pius XI elaborates on the Church' s statement that life begins at conception.

In the 2012 case Texas Medical Providers Performing Abortion Services v. David Lakey, a US appeals court ruled as constitutional a Texas law that required abortion providers in the state to show women receiving abortions the ultrasound images of their fetuses. The law also required providers to describe the sounds of the fetuses' nascent hearts. In doing so, the court set precedent that ultrasound readings are necessary medical information for pregnant women seeking abortions, increasing the wait-period for women seeking abortions. The decision fueled debates in the early twenty-first century US abouts women's rights to abortions.

In the 1973 case State v. New Times, INC, the Arizona Court of Appeals in Phoenix, Arizona, ruled that Arizona Revised Statutes 13-211, 13-212, and 13-213, collectively called the Arizona abortion statutes, were unconstitutional. The statues made it illegal for anyone to receive, provide, or advertise abortion services. The Arizona Court of Appeals reviewed a case in which a city court in Tempe, Arizona, convicted the New Times, a newspaper headquartered in Phoenix, Arizona, of advertising abortion. In hearing the case, the Arizona Court of Appeals deferred to the recently decided US Supreme Court case Roe v. Wade (1973). In Roe v. Wade, the US Supreme Court ruled that women have constitutional rights to abortion services within the first trimester of pregnancy. Accordingly, the Arizona Court of Appeals claimed that all of Arizona's abortion statutes, including the one the New Times was convicted of, prohibited no criminal acts, and set aside New Times's conviction.

A licensed obstetrician and gynecologist, Pearl Tang worked to improve the health of women and children in Maricopa County, Arizona, during the twentieth and twenty-first centuries. Her work with the Maricopa County Health Department ranged from immunizations to preventing cervical cancer. Tang obtained federal grants and community support to establish various child and maternal health clinics throughout Maricopa County as chief of the Maricopa County Bureau of Maternal and Child Health. Tang established mobile clinics, including a clinic she called the Maternity Care Bus, to address the lack of access to medical care among rural women in Arizona. She also focused on family planning through education and the distribution of contraception. Tang's efforts in Maricopa Country increased the delivery of maternal, child, and family planning care and helped lower Arizona's infant mortality rate.

In 2014, the United States Food and Drug Administration published the Pregnancy and Lactation Labeling Rule to amend previous guidelines for the prescription of drugs for pregnant and lactating women. The 2014 Pregnancy and Lactation Labeling Rule was intended to increase the safety and efficacy of prescription drugs by making drug labels easier for physicians to understand and utilize. The Pregnancy and Lactation Labeling Rule restructured drug labels and required that they include narratives describing drug-associated risks to women and fetuses, rather than using complicated letter categories. The Pregnancy and Lactation Labeling Rule changed the framework for drug labeling, making it easier for doctors to prescribe safe and effective drugs to pregnant women, lactating women, and people of reproductive capacity.

Estrogen is the primary sex hormone in women and it functions during the reproductive menstrual cycle. Women have three major types of estrogen: estrone, estradiol, and estriol, which bind to and activate receptors within the body. Researchers discovered the three types of estrogen over a period of seven years, contributing to more detailed descriptions of the menstrual cycle. Each type of estrogen molecule contains a slightly different arrangement or number of atoms that in turn causes some of the estrogens to be more active than others. The different types of estrogen peak and wane throughout women's reproductive cycles, from normal menstruation to pregnancy to the cessation of menstruation (menopause). As scientists better explained the effects of estrogens, they used that information to develop oral contraceptives to control pregnancy, to map the menstrual cycle, and to create hormone therapies to regulate abnormal levels of estrogen.

Margaret Higgins Sanger advocated for birth control in the United States and Europe during the late nineteenth and early twentieth centuries. Although people used contraceptives prior to the twentieth century, in the US the 1873 Comstock Act made the distribution of information relating to the use of contraceptives illegal, and similar state-level Comstock laws also classified discussion and dissemination of contraceptives as illegal. Sanger helped to repeal the Comstock Act and similar laws so that women could legally use contraceptives to control their fertility and the sizes of their families. In 1916, Sanger opened the first birth control clinic in the US in New York City, New York. Later in life, Sanger formed several advocacy organizations that promoted access to contraception, including the Planned Parenthood Federation of America. Sanger's advocacy increased women's access to contraception and helped change the United States' social and legal perceptions of birth control.

Vitamin A (retinol) is an essential vitamin in the daily functioning of human beings that helps regulate cellular differentiation of epithelial tissue. Studies have shown that an excess of vitamin A can affect embryonic development and result in teratogenesis, or the production of birth defects in a developing embryo. Excess intake of vitamin A and retinoids by pregnant women often results malformations to fetuses' skulls, faces, limbs, eyes, central nervous system. Additionally, doctors often use derivatives of vitamin A, known as retinoids, as medicine to treat a number of skin conditions and carcinomas, the most common form of human cancers.