Exactly what can happen if a woman misses one or more days of her birth control pills is highlighted by a new lawsuit: A company that allegedly mislabeled its birth control pills is being sued by more than 100 women who say they became pregnant because of the error.
Pregnancy is especially possible for women who miss birth control pills while using these pills as their only form of birth control, doctors said.
The women involved in the lawsuit reportedly took their birth control pills as instructed on the packaging. Normally, packs of this type of pills include "active" pills that contain hormones, as well as "reminder" pills that contain no active ingredients, but are aimed at helping women to adhere to their daily habit of taking a pill at the same time every day.
However, the pills involved in the lawsuit were packaged "rotated 180 degrees," from their normal position, according to court documents. In other words, the pill packs were labeled upside down — and the reminder pills that should have been taken during the last week of the cycle were instead placed into the first week of the cycle.
As a result, some women took the placebo pill when they were supposed to be taking active pills containing birth control ingredients, such as the hormones estrogen or progestin. [7 Surprising Facts About the Pill]
Among the women involved in the lawsuit, 94 had unexpected pregnancies and gave birth, 17 became pregnant but did not carry to term, and two did not become pregnant, according to CNN.
Normally, among women who take the pill as directed, less than 1 out of 100 women will get pregnant each year, according to Planned Parenthood. But if the pills aren't taken as directed, then about 9 out of 100 women will become pregnant each year, the organization says.
Birth control pills protect against pregnancy in three ways, said Dr. Jill Rabin, the co-chief of ambulatory care and of Women's Health Programs at North Shore Long Island Jewish Health System in New York.
One way is that the pills prevent a woman from ovulating because they maintain a steady level of estrogen and progesterone in the body — a woman needs to have a 24-hour-long spike of estrogen in order to ovulate, Rabin said.
The pill also thickens the cervical mucus, making it difficult for the sperm to get through and reach the egg. And finally, the pill slows the normal movement inside fallopian tubes, making any egg cell that does get released move through the tube more slowly, "so the sperm and the egg just can't get together as easily," Rabin said.
This threefold effect makes pregnancy very unlikely. "Let's say the sperm got by the first step — the thick mucus. But then the movement of the tube is so slow, it's not going to allow the sperm to meet the egg," she said.
However, birth control pills contain low doses of hormone, so it's important to take them daily, Rabin said. Women need to take the progestin-only pill at the same time every day, but the estrogen-progestin pills have a higher dosage, and can be taken within three hours of a designated daily time, she said.
If a woman misses a pill, she should take it as soon as she remembers. However, if she misses two pills, then she should double up for two days, Rabin said. For example, if a woman goes on a trip and forgets her pills on Saturday and Sunday, then she should take two pills on Monday and two pills on Tuesday before going back to her regular schedule, Rabin said. [11 Big Fat Pregnancy Myths]
If multiple pills are missed, then a woman's body might start a new menstrual cycle, experience a spike of estrogen and ovulate, Rabin said. Moreover, if the woman has unprotected sexual intercourse, sperm from her partner can survive in her body for several days, and could fertilize an available egg, Rabin said. (According to Planned Parenthood, sperm can survive up to six days in a woman's body, but that time varies from person to person, Rabin said.)
She encouraged women to call their doctor if they're concerned about a potential pregnancy.
"If you think you might be pregnant from an unintended pregnancy, you should see your doctor so that they can help you," Rabin said. "If you would like to continue the pregnancy, you can get prenatal vitamins and, if not, they can talk to you about other options."
Some other birth control options include the morning-after pill (which can prevent pregnancy from starting, even after intercourse) or an intrauterine device (IUD), according to Planned Parenthood.
However, mislabeled birth control pill packets are a rare occurrence, Rabin said. "I've been practicing a long time and I think this is the first time I've heard something like this," she said.
The pills in the birth-control lawsuit were made by Qualitest Pharmaceuticals, a developer and manufacturer of generic drugs and a subsidiary of Endo Pharmaceuticals, CNN reported. Qualitest Pharmaceuticals recalled the pills in September 2011, according to a Food and Drug Administration safety alert.
The lawsuit concerns "an extremely small number of pill packs that were manufactured by an external contract manufacturer," Endo spokeswoman Heather Zoumas-Lubeski told CNN. "Endo has been able to confirm only one blister pack that manifested a defect and was sold to a patient."
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Laura is the archaeology and Life's Little Mysteries editor at Live Science. She also reports on general science, including paleontology. Her work has appeared in The New York Times, Scholastic, Popular Science and Spectrum, a site on autism research. She has won multiple awards from the Society of Professional Journalists and the Washington Newspaper Publishers Association for her reporting at a weekly newspaper near Seattle. Laura holds a bachelor's degree in English literature and psychology from Washington University in St. Louis and a master's degree in science writing from NYU.