Between 1956 and the early 1960s, researchers tested the first oral contraceptive pill on hundreds of low-income women in Puerto Rico, and the trials were marred by a lack of informed consent, dismissed side effects, and unexplained deaths. The women who participated were largely not told they were taking an experimental drug, and when they reported serious symptoms, the lead investigators pushed forward anyway. These trials produced Enovid, the pill that would reshape reproductive life worldwide, but they did so through methods that violated the basic dignity of the women involved.
Why Researchers Chose Puerto Rico
The choice of Puerto Rico was not incidental. By the mid-1950s, the island had several features that made it attractive to mainland American researchers looking for a large pool of test subjects with minimal regulatory interference. Puerto Rico was a U.S. territory, which meant American researchers could operate there without navigating a foreign government’s approval process. At the same time, the island’s territorial status meant its residents had fewer political protections than mainland citizens. Puerto Rico also had an existing network of family planning clinics, and its colonial government had been actively promoting population control for decades.
Puerto Rico’s poverty was part of the calculus. American policymakers and some Puerto Rican officials had long argued that the island’s economic struggles were caused by overpopulation rather than by the structural inequalities of colonial governance. This framing made birth control a politically palatable intervention on the island at a time when contraception research was still legally and socially contentious in much of the mainland United States. Several U.S. states still had laws restricting contraception, making large-scale clinical trials difficult to conduct domestically.
There was also a practical advantage: Puerto Rico already had high rates of voluntary sterilization, which meant the population was familiar with the concept of fertility control and the local medical infrastructure included clinics oriented toward reproductive services. Researchers could recruit participants through channels that already existed rather than building something from scratch.
The People Behind the Pill
The development of the oral contraceptive was driven by a small group of determined individuals. Gregory Pincus, a biologist, and John Rock, a gynecologist, led the scientific work. Their research was bankrolled largely by Katharine McCormick, a wealthy philanthropist and suffragist who personally funded much of the pill’s development. Margaret Sanger, the birth control activist, had connected Pincus with McCormick and was a driving force behind the project’s ambition to create a simple, woman-controlled contraceptive.
Both Sanger and McCormick were motivated by a genuine belief in women’s reproductive autonomy, but the broader movement they operated within had deep ties to eugenics. Sanger’s own writings and organizational affiliations included eugenic ideas about who should and should not reproduce, and the population-control ideology that shaped American policy toward Puerto Rico carried similar assumptions about the reproductive fitness of poor, non-white communities. The pill’s development cannot be separated from this context. The women who tested the drug were overwhelmingly poor, and the researchers who chose them did so partly because those women had less power to refuse or to demand answers about what they were being given.
How the Trials Were Run
The first large-scale field trials of Enovid began in the Río Piedras housing project in San Juan in 1956. Within a year, over two hundred women had become participants. They were recruited through the local family planning organization, Asociación Puertorriqueña Pro Bienestar de la Familia, known as Profamilia. The trials were coordinated on the ground by Edris Rice-Wray, an American physician who had been living in Puerto Rico since the 1940s, and Iris Rodríguez, a University of Puerto Rico-trained health educator and social worker.1MSU Libraries Digital Collections. More than a way station: ground-level experiences in the field trials of oral contraceptives and IUDs in Puerto Rico, 1956-1966
The pill the women took bore little resemblance to the low-dose formulations available today. Early Enovid tablets contained roughly ten milligrams of the synthetic progestin norethynodrel combined with mestranol, an estrogen. That hormone load was many times higher than what modern pills deliver. Researchers were still figuring out the minimum effective dose, and the women in Puerto Rico were essentially absorbing the consequences of that uncertainty in their own bodies.
The most glaring ethical failure was the absence of meaningful informed consent. Participants were generally told they were receiving a pill to prevent pregnancy, but they were not told the drug was experimental, that they were part of a clinical trial, or that the side effects were unknown. Many women were illiterate, and there is no evidence that the researchers made systematic efforts to ensure participants understood the nature of what they were agreeing to. By the ethical standards of the time, this was already questionable. By any standard since, it was a clear violation.
Side Effects Dismissed
Women in the trials reported a range of side effects including nausea, headaches, dizziness, vomiting, and stomach pain. The complaints were widespread enough that Edris Rice-Wray, the physician supervising the trial on the ground, reported back to Pincus that the pill caused “too many side reactions to be acceptable.” Rice-Wray’s clinical assessment was that the drug, while effective at preventing pregnancy, was producing an unacceptable level of adverse effects in her patients.
Pincus dismissed her concerns. He attributed the women’s complaints to their psychological state rather than to the drug’s pharmacological effects, suggesting the side effects were psychosomatic. This interpretation was convenient for the trial’s progress but unsupported by the evidence Rice-Wray was gathering directly from the women she treated. Her warnings went largely unheeded, and she eventually left Puerto Rico. The pattern here is worth noting: a woman physician reporting what women patients told her, overruled by a male researcher who had never examined the patients himself.
Three women died during the course of the trials. No autopsies were performed to determine whether their deaths were related to the pill. Given that oral contraceptives, particularly high-dose formulations, are now known to increase the risk of blood clots, stroke, and other vascular events, the failure to investigate these deaths is one of the most troubling aspects of the entire enterprise. Whether the pill killed those women is unknown precisely because the researchers chose not to find out.
The Sterilization Campaign That Preceded the Trials
The pill trials did not arrive in a vacuum. Puerto Rico had been the site of one of the most aggressive sterilization campaigns in modern history. Beginning in the 1930s, the island’s government, with encouragement and funding from mainland American interests, promoted surgical sterilization as a solution to poverty. Law 116, passed in 1937, established a eugenics board with the authority to authorize sterilizations, and the practice became so widespread that Puerto Rican women referred to the procedure simply as “la operación.”
By the 1960s, roughly a third of Puerto Rican women of childbearing age had been sterilized, one of the highest rates in the world. Many of these sterilizations were performed on women who were young and under economic or social pressure. A study of 846 sterilized Puerto Rican women found that about one in five expressed some regret, and eleven percent were definitively dissatisfied with the decision. Factors linked to regret included being sterilized at a young age, not having daughters, and having someone else make the decision for them.2PubMed. Sterilization regret among Puerto Rican women
This history matters for understanding the pill trials because it reveals the ecosystem of reproductive coercion that Puerto Rican women were already navigating. Researchers conducting oral contraception trials that sometimes led to sterilization were operating in a context where controlling Puerto Rican women’s fertility was an explicit policy goal, not a side effect of scientific curiosity.3Accountability in Research. Unethical medical treatment and research in US territories The women who joined the pill trials were making decisions within a system that had already normalized the idea that their reproduction was a problem to be solved.
What the Trials Produced
Despite the ethical failures, the trials generated data that Pincus and Rock used to pursue regulatory approval. Enovid was first approved by the FDA in 1957 for menstrual disorders, and then in May 1960, it received approval as an oral contraceptive, becoming the first hormonal birth control pill available in the United States.4PubMed. History of oral contraceptive drugs and their use worldwide The drug contained mestranol and norethisterone, and its approval launched an era of pharmaceutical contraception that has since reached hundreds of millions of women worldwide.
The high hormone doses that caused so many problems in Puerto Rico were gradually reduced in subsequent formulations. Over the following decades, the estrogen content in oral contraceptives dropped dramatically, and newer progestins were developed. The modern pill bears only a family resemblance to what the women in Río Piedras were given. This pharmacological evolution, however, was driven at least in part by the adverse-event data that accumulated after the drug was already on the market, not by the side-effect reports that Rice-Wray had flagged years earlier. The women in Puerto Rico paid the price for safety information that was then used to refine the product for everyone else.
Who Else Was Tested On
Puerto Rico was the largest and most well-known trial site, but it was not the only one. Before the Río Piedras trials, Pincus and Rock conducted smaller-scale tests on patients at Worcester State Hospital in Massachusetts, a psychiatric institution. The patients there, many of whom had severe mental illness, were given the experimental hormones without anything resembling informed consent. They were institutionalized people with no meaningful ability to refuse participation. These tests were primarily used to study the drug’s physiological effects rather than its contraceptive efficacy, since the researchers needed to confirm hormonal suppression of ovulation before moving to a larger population trial.
Trials also took place in Haiti, Mexico City, and among low-income communities in other parts of the United States, though the Puerto Rico trials remain the most extensively documented and the ones most central to the FDA approval process. The consistent thread across all these sites was that the test subjects were drawn from populations with limited social power: psychiatric patients, impoverished women in colonial territories, and marginalized communities within the mainland. The researchers did not test the pill on themselves, their families, or their social peers.
What Informed Consent Looked Like Then and Now
One of the most common defenses offered for the Puerto Rico trials is that informed consent, as we understand it today, did not exist as a formal requirement in the 1950s. This is partly true. The Nuremberg Code, established in 1947 in response to Nazi medical experiments, articulated the principle that voluntary consent is essential for ethical human experimentation. But the Nuremberg Code was not binding law in the United States, and its principles were widely ignored in American medical research for decades afterward.
The formal infrastructure of research ethics that exists today, including Institutional Review Boards, mandatory informed consent procedures, and federal regulations governing human subjects research, did not take shape until the 1970s and 1980s, largely in response to revelations about the Tuskegee syphilis study and other abuses. The Belmont Report of 1979 codified the principles of respect for persons, beneficence, and justice that now govern research ethics in the United States.
But the absence of a formal regulatory requirement does not mean the researchers lacked moral awareness. The Nuremberg Code existed. The concept that experimenting on people without their knowledge was wrong was available to anyone who cared to consider it. Rice-Wray’s own objections show that ethical concerns were raised in real time and overruled. The defense that “things were different then” has some historical validity but obscures the fact that people within the project itself recognized the ethical problems and were ignored.
Lasting Mistrust in Puerto Rican and Latino Communities
The legacy of the pill trials, combined with the broader sterilization campaign, has contributed to deep and durable medical mistrust in Puerto Rican communities. Surveys and qualitative studies consistently find that Puerto Rican and other Latino populations express higher levels of distrust toward medical research and reproductive healthcare than white Americans. This mistrust is not irrational. It is a reasonable response to a documented history of being used as experimental subjects without adequate protection or respect.
This mistrust has practical consequences. It can make recruitment for clinical trials more difficult. It can reduce uptake of new medical interventions. It can lead people to delay seeking care or to reject treatments that might benefit them. Researchers working in these communities today face the challenge of building trust across a chasm that was dug by their predecessors. The unethical treatment of Puerto Ricans in medical research, including but not limited to the pill trials, has been documented as a pattern that includes experiments with total body irradiation and the use of contaminated vaccines, among other abuses.3Accountability in Research. Unethical medical treatment and research in US territories
Acknowledging this history is not just a matter of historical accuracy. Researchers have argued that confronting past abuses could promote higher ethical standards in healthcare and research, particularly for people with diminished autonomy or self-determination.3Accountability in Research. Unethical medical treatment and research in US territories
The Uncomfortable Dual Legacy
The oral contraceptive pill is, by almost any measure, one of the most significant medical advances of the twentieth century. It gave hundreds of millions of women a degree of control over their reproductive lives that had never before been possible. It changed economies, education, family structures, and the trajectory of gender equality in ways that are still unfolding. None of that is in dispute.
What is also not in dispute is that the pill’s development depended on the exploitation of women who had little choice in the matter. The women of Río Piedras did not benefit from the revolution they helped create. They absorbed the highest doses, suffered the worst side effects, and were denied both the information and the agency that ethical research requires. Their contribution was extracted, not given.
This duality is uncomfortable because the instinct to celebrate the pill’s impact can crowd out the reckoning with how it was made. The two things are both true at the same time, and holding them together is the only honest way to tell the story. Modern oral contraceptives are safe and effective precisely because the early versions were neither, and the people who bore the cost of that knowledge were chosen because they were poor, colonized, and expendable in the eyes of the researchers who needed their bodies for data.
Reproductive Coercion Beyond Puerto Rico
The Puerto Rico trials were not an isolated failure. They belong to a broader history of reproductive coercion in the United States that has disproportionately targeted Black, Indigenous, and Latino women, as well as incarcerated and institutionalized populations. Forced and coerced sterilizations were performed on Native American women by the Indian Health Service through the 1970s. Black women in the South were sterilized without consent in such numbers that the practice was known as a “Mississippi appendectomy.” California’s prison system was still sterilizing incarcerated women as recently as 2010.
What connects these episodes is not a single conspiracy but a recurring pattern in which the reproductive capacity of marginalized women is treated as a policy problem rather than a personal right. The Puerto Rico pill trials sit squarely within this pattern. The women involved were not asked what they wanted. They were enrolled in a project designed by people who believed that reducing Puerto Rican fertility was a social good, and who treated the women’s complaints, their pain, and even their deaths as acceptable costs of progress. Understanding the pill trials in isolation risks treating them as a one-time error. Understanding them in context reveals them as one chapter in a much longer story that is not yet finished.