Here's the Science of How Abortion Pills Work

Sam Westreich, PhD

The science behind the pill that’s become the most controversial bit of telemedicine.
If the COVID vaccine was a pill instead of a shot, would it be more acceptable?Photo byPhoto by danilo.alvesd on UnsplashonUnsplash

Inthe United States of America, abortion, always a hot-button issue, has now become one of the major concerns that may drive elections and positions over the next couple years. With the Supreme Court repealing Roe v. Wade, the issue has gone to the individual states. Some have pushed for bans on abortion, while others look to expressly codify it as a guaranteed right.

This difference in stances between states has led to a rise in prescriptions and distributions of the abortion pill. Previously, abortions were more commonly an in-person medical procedure; now, more than half of them are done by medication instead.

Abortion pills offer a clear advantage for women living in states that have bans on abortions; they can be obtained remotely, instead of requiring in-person travel. This telemedicine, where someone gets a prescription from a doctor without an in-person visit, is on the rise in our increasingly internet-connected on-demand society.

But how does an abortion pill work? How can a pill replace a surgical procedure? Let’s look at the science behind this solution.

Pregnancy is a hormone driven process

Inside the body, large-scale changes are driven by signaling molecules, which trigger complex downstream effects. These signaling molecules are called hormones, and humans have plenty of them. These include:

  • Adrenaline, the “fight or flight” hormone that boosts heart rate and preps muscles for strenuous activity;
  • Testosterone, the primary sex hormone in men that drives development of the male reproductive system, as well as boosting muscle and bone growth;
  • Estrogen, one of the female sex hormones that drives development of the female reproductive system;
  • Progesterone, a steroid hormone that helps drive the female reproductive cycle, as well as regulating the progress of a pregnancy.
  • Human Chorionic Gonadotropin, often abbreviated as hCG, is a pregnancy-associated hormone produced during early pregnancy. It’s often the indicator in lab tests to determine whether someone is pregnant.

Our focus is going to be on that last two hormones, progesterone and hCG.

When an egg is fertilized, it implants in the uterus. But this isn’t a safe long-term spot, on its own. The uterine lining is regularly shed and re-grown, a process which happens on a fairly regular cycle that we call the menstrual cycle. (When a woman gets her period, it’s the passing of the shed uterine lining.)

If the fertilized egg doesn’t send a signal to the rest of the body saying “Hey, I’m here, don’t flush!”, it would get expelled at the next period! We can’t have that.

So once the egg implants into the uterine wall, it triggers the formation of the placenta, the support system that exchanges nutrients and waste between the baby and the mother.

The placenta also starts producing hCG, pumping it into the bloodstream of the mother.

The hCG hormone acts as a signal to the mother’s body, calling out that she’s pregnant. It starts appearing about 10–11 days after conception and keeps on increasing in level as the placenta grows, eventually peaking at around week 10 of the pregnancy.

The hCG triggers increases in production of other female hormones, in a cascading sequence. namely estrogen and progesterone. That increase in progesterone is really important; it thickens the uterine lining, stops any additional eggs from being released, and even stimulates the release of nutrients for the growing embryo.

Without the surge in hCG and the following steady release of progesterone, a pregnancy won’t progress.

And this is where our intervention comes in.

The “abortion pill” is actually two different pills, both needed

The abortion pill is actually two pills, each containing a different medicine. The first pill contains a medication called mifepristone, while the second pill contains a different medication called misoprostol. The names may look similar, but their effects are different.

Mifepristone is a progesterone blocker. It works by serving as what we call an antagonist; it binds to a receptor but blocks it from activating.

Progesterone gets its signal across by activating receptors on various cells that are sensitive to it. When progesterone binds to the receptor on the outside of the cell, it triggers actions to happen inside the cell.

But if mifepristone binds to that progesterone receptor instead, it blocks the receptor from being reached by the actual progesterone, and the receptor isn’t activated. It’s like if someone stuffs a pumpkin into a mailbox; the mail can’t be delivered, and the mailbox owner won’t receive any messages.

Thus, mifepristone stops the pregnancy from progressing by blocking the signaling cascade, leading to menstrual bleeding, disruption of the endometrium, and then termination of the pregnancy.

After mifepristone, usually 1–2 days later, the person takes the second pill, containing misoprostol. Misoprostol drives the cervix to soften and the uterus to contract. This helps to expel the remains of the embryo after the pregnancy has been interrupted by the mifepristone.

The end result is bleeding, usually heavier than the typical period, as the pregnancy is expelled. This can occur as early as after the first pill, but is more common in the few hours following the consumption of the misoprostol pill.

Differences between the pill versus surgery

The abortion pill is typically only prescribed up until the 9th week of pregnancy, although this can vary somewhat by state. As mentioned, some states have outlawed abortion, so someone seeking an abortion in that state would need to reach out to an out-of-state doctor.

A surgical abortion, on the other hand, can often be obtained up until week 16 of pregnancy, although it may be performed as late as week 24 in rare cases when there is a significant medical risk.

So, beyond a certain stage (approximately 2 months), the pill is no longer an option.

There’s also a trade-off in terms of time needed. The pill approach takes a day or longer, while the surgical intervention can be completed in as few as 5–10 minutes.

And finally, there’s the question of assistance and reassurance. Having an abortion can be a very emotional experience. Having an in-patient surgical intervention also gives a patient the opportunity to speak with doctors and nurses, who may be able to offer reassurances or other assistance, which wouldn’t be available with an at-home option.

In summary: disrupt the hormones, stop the pregnancy

The “abortion pill” is growing more popular, as it can be consumed by pregnant women at home and can be prescribed remotely and distributed by mail, allowing access even in states where new laws have placed partial or total restrictions on abortion.

The pill is actually two pills, each containing a different medicine. Mifepristone, in the first pill, blocks progesterone, while misoprostol, in the second pill, loosens the uterine lining and softens the cervix so the pregnancy can be expelled.

The abortion pill is generally only prescribed for pregnancies that are less than 2 months along; beyond that point, a surgical intervention is usually recommended instead.

It’s sobering to know that hormones control so much of our processes. Disrupt the hormones, and you can alter the body’s functions — such as terminating an unwanted pregnancy.


Want to subscribe to NewsBreak for all the most up-to-date news? Click here.

Want to earn money by writing for NewsBreak? Sign up here.

Comments / 0

Published by

A microbiome scientist working at a tech startup in Silicon Valley, Sam Westreich provides insights into science and technology, exploring the strangest areas of biology, science, and biotechnology.

Mountain View, CA

More from Sam Westreich, PhD

Comments / 0