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After the success of the preliminary Boston trials for the Pill in 1954 and 1955, John Rock and Gregory Pincus were confident they had honed in on an oral contraceptive. But without large-scale human trials, the drug would never receive the FDA approval necessary to bring the drug to market. Given the strong legal, cultural and religious opposition to birth control in America in the 1950s, the prospects for this crucial next step appeared dim.

A Perfect Location

In the summer of 1955, Gregory Pincus visited Puerto Rico, and discovered it would be the perfect location for the human trials. The island, a U.S. territory, was one of the most densely populated areas in the world, and officials supported birth control as a form of population control in the hopes that it would stem Puerto Rico's endemic poverty. There were no anti-birth control laws on the books, and Pincus was impressed with the extensive network of birth control clinics already in place on the island. There were 67 clinics dispensing existing methods of birth control and a large group of women used their services.

Poor, Uneducated Women

For Pincus, the island offered a pool of motivated candidates, and a stationary population that could be easily monitored over the course of the trials. Pincus also knew that if he could demonstrate that the poor, uneducated, women of Puerto Rico could follow the Pill regimen, then women anywhere in the world could too. Pincus hoped that by showing Puerto Rican women could successfully use oral contraceptives, he could quiet critics' concerns that oral contraceptives would be too "complicated" for women in developing nations and American inner cities to use.

Rio Piedras

The base for the first trial was a clinic at Rio Piedras, a brand new housing project complete with running water and sunny balconies just outside of San Juan. The worst slum on the island, El Fangito ("the little mud hole"), had been razed to build clean, white seven-story buildings, and the new residents were eager to continue to improve their standard of living. Many American companies were building factories on the island, and plenty of factory jobs were available for local women.

Many Trial Subjects

The Rio Piedras trials quickly got off the ground in April 1956. In no time, the trial was filled to capacity, and they expanded the trials to additional locations on the island. Although Puerto Rico was a predominantly Catholic island, people were far more concerned with the struggles of daily life than Church dogma, and did not follow Rome on matters of birth control. At the time, most women relied on sterilization or abortion to limit their family size, and the Pill was a welcome alternative.

Initial Dosages

The pharmaceutical company G.D. Searle provided the pills for the trial. Rock selected a high dose of Enovid, the company's brand name for their synthetic oral progesterone, to ensure that no pregnancies would occur while test subjects were on the drug. Later, after discovering Enovid worked better with small amounts of synthetic estrogen, that active ingredient was added to the Pill as well.

100% Effective

Dr. Edris Rice-Wray, a faculty member of the Puerto Rico Medical School and medical director of the Puerto Rico Family Planning Association, was in charge of the trials. After a year of tests, Dr. Rice-Wray reported good news to Pincus. The Pill was 100% effective when taken properly. She also informed him that 17% of the women in the study complained of nausea, dizziness, headaches, stomach pain and vomiting. So serious and sustained were the reactions that Rice-Wray told Pincus that a 10-milligram dose of Enovid caused "too many side reactions to be generally acceptable."

Dismissing Side Effects

Rock and Pincus quickly dismissed Rice-Wray's conclusions. Their patients in Boston had experienced far fewer negative reactions, and they believed many of the complaints were psychosomatic. The men also felt that problems such as bloating and nausea were minor compared to the contraceptive benefits of the drug. Although three women died while participating in the trials, no investigation was conducted to see if the Pill had caused the young women's deaths. Confident in the safety of the Pill, Pincus and Rock took no action to assess the root cause of the side effects.

Deceit and Exploitation?

In later years, Pincus's team would be accused of deceit, colonialism and the exploitation of poor women of color. The women had only been told that they were taking a drug that prevented pregnancy, not that this was a clinical trial, that the Pill was experimental or that there was a chance of potentially dangerous side effects. Pincus and Rock, however, believed they were following the appropriate ethical standards of the time. In the 1950s, research involving human subjects was much less regulated than it is today. Informed consent standards were minimal and only the most basic toxicity tests were required for human trials.

Questions Linger

To this day, questions linger over whether Pincus and Rock overlooked serious side effects from the original high dosage Pill during trials, in their rush to bring an effective pill to market. The dosage of the Pill has since been dramatically lowered and the incidence of serious side effects has been greatly reduced. Still, the Puerto Rico pill trials remain a controversial episode in the history of the Pill's development.