The FDA in 2000 approved mifepristone to terminate pregnancies of up to 10 weeks, when used with a second drug, misoprostol. Mifepristone is taken first to dilate the cervix and block the hormone progesterone, which is needed to sustain a pregnancy. Misoprostol is taken 24 to 48 hours later, causing the uterus to contract and expel pregnancy tissue.
Bleeding is a common side effect, though serious complications are very rare. The FDA says more than 3.7 million U.S. women have used mifepristone since its approval.
the pills are most often recommended for pregnancies less than 10 or 11 weeks.
Medication abortions are not a good option for those whose pregnancy has progressed too far.
Others who should not use abortion pills, says Gariepy, are people who have a rare disorder called porphyria, are on chronic steroids, have had a previous allergy to mifepristone, or are severely anemic.
The Cleveland Clinic also notes that medication abortions are not safe for those who have a blood clotting disorder, chronic kidney failure or have an IUD (intrauterine device).
They're also not a good choice to treat an ectopic pregnancy (a pregnancy outside the uterus), or for those who don't have access to emergency medical care or can't do a follow-up consultation, the clinic says.
Plan B is emergency contraception, not an abortion. Plan B and another drug called Ella work by delaying or preventing ovulation. Plan B is most effective if taken within three days after unprotected sex; Ella can be taken within five days. Both are more effective the sooner they are taken.