Which contraceptives can act as abortifacients?

In the last 10 years, chemical abortion use has exploded, and by now pro-lifers are well aware of the two-step abortion pill process using mifepristone and misoprostol. The express purpose of these abortifacients is clear: ending a growing, developing human life.

But confusion remains about whether and which contraceptives – including hormonal contraceptives, IUDs, and emergency contraception – may also sometimes cause early abortions, aka act as abortifacients, unbeknownst to the women taking them. 

Here’s what to know. 

Key Takeaways:

• Pro-abortion advocates claim contraceptives cannot be abortifacients when they prevent implantation, because they changed the definition of pregnancy in 1965 to coincide with implantation, which occurs 6-12 days after fertilization (the beginning of a new human being).

• Hormonal contraceptives can work through three mechanisms of action: stopping ovulation, thickening cervical mucus, and thinning the uterine lining to prevent implantation. However, some contraceptives may not employ all three mechanisms.

• Emergency contraceptives, hormonal contraception, and IUDs may, in varying degrees, act as abortifacients. It depends on their mechanisms of action, and there are still unknowns in some cases.

What is an abortifacient?

An abortifacient is any drug or medication that causes an abortion, according to Merriam-Webster. 

There is a major discrepancy between pro-life and pro-abortion perspectives on what constitutes an abortion. The discrepancy comes down to a politically-driven re-definition back in 1965, which was further clarified and affirmed in 1972, by the abortion-promoting professional organization for reproductive health practitioners, the American College of Obstetricians and Gynecologists (ACOG). 

Specifically, ACOG moved the goalposts to define a pregnancy as beginning, arbitrarily and inexplicably, when the newly created human life implants in the uterus (this happens between 6-12 days after fertilization). This is in contrast to recognizing that life begins at fertilization, also known as conception, when the sperm and egg meet and a genetically distinct human life is created. 

According to pro-abortion advocates and ACOG, contraceptives can’t be called abortifacients when they prevent implantation because pregnancy ‘hasn’t happened yet.’ But pro-lifers understand that contraceptives are, in fact, abortifacient if they prevent the newly conceived human life from burrowing or implanting in the uterine lining, also called the endometrium. 

Can hormonal contraceptives be abortifacient?

How hormonal contraceptives work

Oral hormonal contraceptives have three mechanisms of action, or ways that they work, to prevent pregnancy.

In total, this medically-reviewed Flo health article notes that the hormonal birth control pill, patch, arm implant, vaginal ring, shot (Depo-Provera), and hormonal IUD generally work in the same ways to prevent pregnancy (There are some qualifications for the hormonal IUD; more on this below, and for the arm patch, for which Mayo Clinic mentions Mechanism of Action #1 and #2, but does not mention #3). 

Mechanism of action #1: Stop ovulation

First, hormonal contraceptives prevent ovulation from occurring.

This helpful Healthline article succinctly summarizes the specific ways synthetic estrogen and progesterone (called progestin) in oral contraceptives prevent the release of hormones that would normally lead to ovulation. 

Because today’s oral contraceptives have much lower estrogen dosages than when they were first developed, "breakthrough” ovulation occurs more frequently now than it used to. 

What’s more, timing matters for hormonal birth control’s ability to prevent ovulation. ‘Typical use,’ meaning occasionally skipping a pill or not taking it at the same time each day, results in 9 unintended pregnancies per 100 users per year, revealing that ovulation wasn’t prevented in those cases. 

Also of note, progestin-only oral contraceptives are less likely to prevent ovulation than pills that contain both estrogen and progestin. This ACOG FAQ explains that fully 40% of women taking progestin-only pills, aka the mini-pill, will continue to ovulate. 

Mechanism of action #2: Thicken cervical mucus

Second, hormonal contraceptives work to thicken the cervical mucus to prevent sperm from swimming through it and meeting the egg for fertilization. 

Mechanism of action #3: Thin uterine lining to prevent implantation

Third, oral contraceptives keep the uterine lining (endometrium) thin so that if breakthrough ovulation occurs and fertilization happens, the newly conceived human life – now at the blastocyst stage of development – cannot implant there. For readers interested in the specific research on hormonal contraceptive use and possible implantation prevention, this 2019 research review sums up what’s known about “embryocidal postfertilization mechanisms of action” of hormonal contraception.

Can IUDs be abortifacient?

As previously covered in an article on whether IUDs may be abortifacient, there are two kinds of intrauterine devices (IUD): the hormonal IUD or levonorgestrel-IUD (LNG-IUD) and the copper IUD or Paragard. 

Hormonal IUD

The LNG-IUD is a progestin-only IUD and ovulation prevention is not its main goal. Within a few years of insertion, the majority of cycles are ovulatory. 

The manufacturer explicitly states that the exact mechanism of action for pregnancy prevention “has not been conclusively demonstrated” and could include “thickening of cervical mucus preventing passage of sperm into the uterus, inhibition of sperm capacitation or survival, and alteration [read: thinning] of the endometrium.” 

Copper IUD

The Paragard or copper IUD primarily prevents pregnancy by continuously releasing copper ions into the uterus, which disable sperm and prevent it from traveling to reach and penetrate the egg. As its manufacturer notes, “Mechanism(s) by which copper enhances contraceptive efficacy include interference with sperm transport and fertilization of an egg, and possibly prevention of implantation.” Prevention of ovulation is not the goal of the Paragard IUD.

If IUDs don’t primarily prevent ovulation and they may prevent implantation, and early postfertilization but preimplantation pregnancy loss may occur. This 2019 research review, by many of the same authors as the research review referenced above, sums up what is and isn’t known about IUDs causing early abortions. 

Can emergency contraception be abortifacient?

As previously covered, there are two different “emergency contraceptives” taken to prevent pregnancy up to five days after unprotected sex. They are Plan B and Ella. 

Ella made the news in 2025 as a possible replacement for increasingly-regulated mifepristone in the two-step abortion pill regimen. For that study, it was given at twice the dose as for emergency contraception. Similarly to mifepristone, Ella is a selective progesterone receptor modulator, meaning that it can block the pro-pregnancy effects of progesterone in the uterus, causing an early abortion. 

Luteal phase defects and Plan B

There’s more nuance around whether Plan B can be abortifacient. 

Scientific research usually measures successful ovulation by a) rupture of a mature follicle (and release of the egg that was inside, which is now available for fertilization), and b) a certain rise in progesterone (which is produced by the corpus luteum, the leftovers of that ruptured follicle).

But hormonal contraception and in particular emergency contraception can prevent healthy progesterone rise in the second part (luteal phase) of the cycle. This is called a luteal phase defect. If significant enough, ovulation could occur (and possibly fertilization), but research wouldn’t catch or capture it because of the Plan B-caused lack of progesterone rise. 

But how often might Plan B actually be abortifacient?

As excellently outlined in this 2014 article, there are “nine critical steps from fertilization to a successful pregnancy that proceeds to term.”

Potentially abortifacient Plan B action could only possibly occur at step three, specifically when taken during the one to two days immediately before ovulation. In these cases, taking Plan B might cause a luteal phase defect, a.k.a. too little progesterone for successful nourishment and implantation of the blastocyst. Without nutrients or a safe, healthy place to grow, the blastocyst can’t continue developing, leading to a very early abortion. 

There’s much discussion over how often Plan B might actually be abortifacient as opposed to only contraceptive, or altogether ineffective at preventing pregnancy. And in 2023, based on available research, the manufacturer removed language about Plan B possibly having mechanism of action #3 mentioned above, ability to thin the endometrium and prevent implantation.

The Bottom Line:

So can emergency contraceptives, hormonal contraception, and IUDs act as abortifacients? To varying degrees, yes.