Emergency contraception sales spike after New Year's. Here's why — and how the pills prevent pregnancy.

Unprotected sex on New Year’s Eve may be driving a spike in sales of emergency contraception after the holiday, according to a new study published in the British Medical Journal. In the study, researchers looked at marketing data on weekly aggregated sales of emergency contraception between 2016 and 2022 and found that sales significantly increase following the new year holiday celebrations.

While other major national holidays, such as Valentine’s Day, St. Patrick’s Day and Independence Day, also see a rise in sales, the demand for emergency contraception is greatest after New Year’s, Dr. Nap Hosang, co-founder of Cadence OTC (who was not involved in the study), tells Yahoo Life.

There are several reasons behind the surge. "The number of unplanned sexual encounters increases during this time period,“ women’s health expert Dr. Jennifer Wider, tells Yahoo Life. Hosang agrees, adding that “alcohol consumption probably is a factor in reducing our usual inhibitions on holidays like this. Clusters of increased social activities where alcohol consumption is also present increase the chances of unprotected spontaneous sexual encounters,” including sexual assault. So it’s understandable that people would reach for emergency contraception since it helps prevent pregnancy after unprotected sex.

So how does emergency contraception work?

Although they’re sometimes lumped into the same category, emergency contraception is different from the prescription pills used in a medication abortion, since it prevents pregnancy from happening in the first place. Emergency contraception “and in particular the one reported in this publication — levonorgestrel — work by delaying the release of the female egg from the ovary, and in this way prevents sperm from finding an egg to fertilize,” explains Hosang. “It will not work if the egg was released just before taking the [emergency contraception] pill. This is why taking emergency contraception as soon as possible after unprotected intercourse is best.”

What are the different types of emergency contraception?

There are a few options when it comes to emergency contraception. One is pills that contain levonorgestrel, such as over-the-counter Plan B One-Step, My Way, Take Action and generic versions. Levonorgestrel is a type of progestin that’s found in other birth control pills, but for emergency contraception it’s offered “at a higher, one-time dose to delay ovulation,” Dr. Melissa Myo, a clinical instructor of obstetrics and gynecology at USC’s Keck School of Medicine, tells Yahoo Life.

The second type is an oral medication that contains ulipristal acetate, which acts like levonorgestrel by inhibiting ovulation and is sold by prescription under the brand name Ella as well as in generic form. Both types of pills — levonorgestrel and ulipristal acetate — can be taken up to five days after having unprotected sex to prevent pregnancy. But sooner is better when it comes to emergency contraception. “They work much better if you take them during the first three days,” according to Planned Parenthood.

Although they're less well known, copper IUDs can also be used as a form of emergency contraception. Copper IUDs, which are inserted by a doctor or nurse, work “by interfering with sperm function” — copper is toxic to sperm — “and can be a good option for someone who is interested in not only preventing this pregnancy but also in starting a longer-term contraceptive method,” Myo explained.

Copper IUDs should be inserted within five days of unprotected sex and are more than 99% effective in preventing pregnancy, according to the World Health Organization. Emergency contraceptive pills are also highly effective, particularly when taken within three days of having unprotected sex. But, according to Planned Parenthood, Ella is the most effective morning-after pill.

It’s worth pointing out, however, that for people who weigh over 165 pounds, levonorgestrel morning-after pills may not work, and those that weigh 195 pounds or more Ella may be less effective, according to Planned Parenthood. Copper IUDs, on the other hand, typically work well regardless of weight.

Wider recommends being prepared by having emergency contraception on hand. "Taking precautionary measures is key because not every pharmacy will have emergency contraception," she says, "so planning ahead of time can help prevent a delay in case you truly need it."