EllaOne is a new emergency contraceptive that can work up to 5 days after unprotected intercourse.  This is a significant advantage over the existing levonorgestrel (Plan B), which only works for 3 days.

There is the concern, however, that ellaOne’s could in theory induce an abortion.

Emergency contraception

When a woman has unprotected sex and is in the fertile part of her cycle, the risk of becoming pregnant can be as high as 9%, according to a Princeton health website.

This is a problem as an unexpected pregnancy can cause significant life disruption and the mother may not be properly prepared to raise a child.

Emergency contraception is taken after unprotected sex and acts to prevent pregnancy.

How does it work?

EllaOne is a progesterone receptor modulator.  It acts to block the action of progesterone in your body.  The key concern is how does this prevent pregnancy.

On the one hand, progesterone plays a role in ovulation and preparation of the egg in the woman for fertilization by a sperm.  Since it can take a while for sperm to fertilize an egg, blocking this action may prevent the egg from being fertilized.  This would prevent a pregnancy from happening.

On the other, blocking the action of progesterone can also induce abortions.  This is because it plays a role in the development and support of the fetus.

How well does ellaOne work?

EllaOne works at least as well as Plan B and likely works better.  In one study of 2221 women after unprotected sex, there were 15 pregnancies in those who took ellaOne as opposed to 22 pregnancies in those who took Plan B.

The difference between ellaOne and Plan B was most strongly seen in action after 3 days, where ellaOne had a significant advantage.  In that study, all women who had pregnancies when taking the pill more than 3 days after unprotected sex were on Plan B.

What are the concerns?

The main concern around ellaOne is that it could act to induce abortion.  This would highly increase the controversy around its use and could lead to difficulty in being approved.

Proponents of ellaOne argue that it is the inhibition of ovulation and blocking of the pre-fertilization stage that are its mechanism of action.

Other concerns include its high price and possible less efficacy in obese women.

Emergency contraception in general

Some data indicates that access to emergency contraception has very little impact on actual rates of pregnancies.  This could be due to lack of education and limited awareness of treatment options and their appropriate timing.

Some surveys show that very few doctors talk to their at risk patients about emergency contraception, even gynecologists.  One survey showed that only 4% of women seeing a gynecologist reported learning about emergency contraception.

New Drugs

If you want to learn about other new drugs, see here.


1) Ulipristal acetate versus levonorgestrel for emergency contraception: a randomised non-inferiority trial and meta-analysis
2) Emergency contraception, efficacy and public health impact



All content on this site is strictly for INFORMATION PURPOSES ONLY. Please consult your doctor for any advice regarding your condition.