Accidents happen, condoms break — and when you find yourself in that position, it's good to know you have the option of taking emergency contraception. But is there anyone who shouldn't take the morning-after pill? In short, no. Melisa Holmes, MD, FACOG, cofounder of Girlology, assured that the morning-after pill is "incredibly safe for anyone at risk for pregnancy, including teens." However, there are some situations where the pill may not be as effective.
For example, "studies have shown that emergency contraceptives lose effectiveness as body mass index increases," Dr. Holmes told POPSUGAR. Specifically, prescription-only pills containing Ulipristal may be more effective for people with a BMI over 30 than the progestin-only formulas that are available over-the-counter. However, Dr. Holmes stressed that this doesn't make the pill unsafe, and some form of protection is better than none at all. If you're concerned, she suggests talking to your healthcare provider about a more reliable form of emergency contraception, like a copper IUD.
Meedlen Charles, MD, a board-certified ob-gyn at New York-Presbyterian Hudson Valley Hospital, added that some medications — such as anti-seizure drugs and antiretrovirals used to treat HIV — could potentially make emergency contraception less effective. If you're on a medication that may affect how your body absorbs the pill, it's important that you discuss your options with a doctor.
Otherwise, the efficacy of the morning-after pill largely depends on the timing — Dr. Charles warned that the longer you wait to take the pill, the less effective it'll be. Dr. Holmes noted that progesterone-only emergency contraceptives like Plan B won't prevent pregnancy once an egg has been fertilized, nor will they harm an established pregnancy. "It's important to note that progesterone is a hormone sometimes prescribed to someone with a history of early miscarriages to support an early pregnancy," Dr. Holmes said. "So, if you take an EC and find out you're already pregnant, there's no need to worry."