Politics & Policy

Contraception after Conception?

Some common contraceptives can kill embryos, not just keep them from forming.

This is not an article about the morality of contraception. This is an article about a very specific scientific question: What happens to embryos formed while the mother is using modern methods of contraception? This information is of importance to some women choosing contraception. And, unlike 20 years ago, today’s science has much to say about the conditions that embryos face when they are formed in women using contraception.

All methods of contraception can fail to prevent a recognized pregnancy. Statistics on how often a method permits a recognized pregnancy are published by the CDC. For example, using the CDC numbers, for every 100 women who use the Pill for one year, nine will have a recognized pregnancy.#ad#

What do these numbers mean regarding embryos? Pregnancy, as recognized by the CDC numbers, is the tip of the iceberg when it comes to counting the number of actual embryos formed. This is why:

There is a two-week period of uncertainty between the time the embryo is formed by fertilization and the time a pregnancy test turns positive. There is no test to know for certain if a woman is carrying an embryo in these two weeks. We can test for whether or not a woman releases an egg (which must happen for fertilization to occur) and whether or not the embryo survived to give a positive pregnancy test. In normal, non-contracepting women, we know that some embryos are formed each cycle but do not survive to give a positive pregnancy test.

But is that number of embryos who die increased by a particular type of contraceptive drug or device? This is a key question for many women of conscience.

Put another way: Is there any evidence that an embryo formed during the use of a certain kind of contraceptive drug or device might face an environment in which the embryo is likely to be damaged or destroyed? The answer depends on the kind of contraceptive drug or device used.

Fertility awareness methods (FAMs): FAMs rely on a couple to understand the timing of the woman’s fertile period and avoid the possibility that sperm could contact an egg during that time. Once released, sperm live for five days in a woman’s reproductive tract. An egg can be fertilized only within 24 hours of its release from the ovary. Combining these two facts gives couples the ability to time sex so as to either achieve or avoid pregnancy. There are no studies showing that embryos conceived during the use of FAMs fare any worse than embryos in women who do not use contraception.

Barrier methods: Barrier methods of contraception, such as condom and foam, or diaphragm and spermicidal jelly, form a mechanical barrier to keep sperm from coming in contact with the egg. The diaphragm or condom mechanically prevents the sperm from contacting the cervix. The spermicidal jelly or foam damages or kills sperm that escape the mechanical barrier. However, normal semen contains millions of sperm in each cc, and it takes only one to fertilize an egg and form an embryo. If an embryo is formed despite the use of a barrier method with spermicide, there is currently no evidence that the embryo will be harmed by exposure to the spermicide. (Small studies in the 1980s that raised concern about an increase in birth defects among children conceived during the use of spermicides were not confirmed by larger studies.)

Embryo formation is much rarer with permanent barrier methods, such as tubal ligation or vasectomy. If an embryo forms in a woman who has had a tubal ligation, that embryo is at a higher risk of implanting in the scarred fallopian tube rather than in the womb, creating an ectopic pregnancy. An ectopic pregnancy is life-threatening for the woman, since if the tube ruptures, she can bleed to death quickly. Fortunately, this situation is not common, but it is a known risk of tubal-ligation failure. When a vasectomy fails, meaning that sperm are still present in the man’s semen, the sperm are often abnormal. But currently there are no studies that show an increase in abnormal pregnancies fathered by men with a failed vasectomy, or after a vasectomy reversal. So other than the issue of ectopic pregnancies, embryos formed during the use of barrier methods seem to fare as well as embryos conceived without exposure to barrier methods.


Anti-progesterone drugs: Drugs such as RU-486 (mifepristone/Mifeprex) and Ella (Ulipristal/Ella-One) work by blocking a hormone necessary for embryos to live. RU-486 is the drug approved by the FDA to cause abortion. Ella is a second-generation version of RU-486. The two drugs work the same way in a woman’s body. If either Ella or RU-486 is given several days before ovulation is expected, it can cause the egg release to be delayed several days. This is the basis of advertisements in which the manufacturer of Ella states that the mechanism of action of Ella is to delay ovulation. But that is not the mechanism of action when Ella is taken only shortly before egg release, or after egg release.

When Ella or RU-486 is taken after the embryo has formed, it blocks the action of progesterone. Progesterone prepares the mother’s body to allow the embryo to implant. When progesterone is blocked, the embryo cannot implant, or it implants imperfectly and subsequently “miscarries.” This was demonstrated clearly in the FDA trials that led to approval of Ella as an “emergency contraceptive.” So both Ella and RU-486 (and other drugs of this type) can clearly produce an environment in the woman’s body that damages or destroys embryos.#ad#

Intra-uterine devices (IUDs): IUDs work by putting a foreign body into the woman’s womb. The IUD then causes an inflammation inside the womb, much like the inflammation that forms in the skin when you have a splinter. This has a contraceptive effect because implantation of an embryo in the uterine lining involves a complicated cross-talk between the immune cells of the mother and those of the embryo. In the presence of chronic inflammation caused by the IUD, implantation is difficult or impossible.

The IUD clearly does not prevent the formation or release of eggs. Studies of egg-release rates among women using the IUD show rates just slightly lower than those among women without IUDs. Studies have also shown that when early embryos are recovered from the fallopian tubes of IUD users, most of these embryos are damaged. IUDs have also been used as very effective “late” emergency contraception, because if an IUD is inserted after an embryo implants, it can disrupt the implantation and cause the death of the embryo.

Hormonal contraceptives: The mechanism of action of hormonal contraceptives has been hotly debated in the scientific literature for more than two decades. Current research demonstrates that hormonal contraceptives most often work by delaying or preventing an egg from being released. But recent research has also found other effects of hormonal contraceptives, such as changes in the structure and function of the lining of the womb, and changes in the hormone-secretion process from the ovaries. These changes can be enough to prevent the embryo from implanting, causing the embryo to die.

What is known about the different kinds of hormonal contraceptives and their effects on embryos?

(1) Emergency hormonal contraceptives (Plan B): Plan B is a large dose of an artificial progesterone-like compound called a progestin. When Plan B is taken two to four days before a woman is due to release an egg, it will delay the egg release. So if a woman is exposed to sperm two to four days before she is due to release an egg, and she takes Plan B, that will likely delay the egg release long enough that the sperm will die beforehand.

But if she takes Plan B one day before egg release, the ovary will still release an egg, and the egg will have the same chance of fertilization as if she had not taken Plan B. However, she will likely not get pregnant. Why? It turns out that Plan B taken one day before egg release interferes with the woman’s ability to produce her own progesterone. And without enough of her own progesterone, the lining of the uterus will not produce the optimal changes necessary to allow the embryo to implant.

If the woman takes Plan B one or more days after egg release, then the drug will probably do nothing.

So Plan B really works only if taken during a certain five out of 30 days of each monthly cycle. On one of those days, it is likely that Plan B will allow an embryo to form, but will result in changes to the lining of the uterus that make implantation difficult.


(2) Continuous hormonal contraceptives (“birth-control pills”):

While it is clear that the early birth-control pills in the 1950s and 1960s kept a woman from releasing an egg, the high dosage of estrogen responsible for such ovarian suppression also caused strokes, blood clots, and heart attacks, among other life-threatening problems. In the 1980s and 1990s the dosage of estrogen was lowered and estrogen-related toxicity decreased. But the lower the dose of estrogen, the more likely it is that the ovary will release an egg. This left researchers in the unsettling position of finding more and more egg release with low-dosage pills, but the same effectiveness in preventing detectable pregnancies as with high-dosage pills.

If there are more eggs released and the same number of pregnancies, what happened to those eggs? Are embryos formed? What happens to those embryos?

#ad#While the jury is still out about whether or not the “birth-control pill” causes embryos to die, there is sufficient research to suggest it is a real possibility. The matter is quite complicated, but one recent scientific review of how birth-control pills work states that in most cases, the pills prevent eggs from being released. But the same study also stated that birth-control pills change the lining of the uterus, so that if an egg is released, and an embryo is formed, then implantation will be more difficult or impossible and the embryo will die.

This is the ethical problem that confronts people who do not want to cause the death of a human embryo. It may be true that birth-control pills usually work by preventing eggs from being released, but sometimes eggs are released and embryos are formed. And the environment that those embryos face inside their mother likely makes it difficult for them to survive and flourish.

The terms “contraceptive,” “pregnancy,” and “abortion”: How can actions that kill an embryo after it has formed be called “contraception”? The answer is semantics. The word “abortion” is defined as the “termination of an established pregnancy.” While most of the scientific world (and most of the world in general) understands pregnancy to begin at fertilization, in the 1960s the American College of Obstetricians and Gynecologists (ACOG) redefined “pregnancy” as beginning at the completion of implantation. Implantation happens a week after the embryo has been formed, when the embryo snuggles into the lining of the mother’s womb and begins to intertwine blood vessels with the mother’s for nourishment. According to the ACOG definition, only after implantation is complete does “pregnancy” happen. This terminology is now entrenched in the legal literature. So, according to this thinking, preventing implantation is semantically “preventing pregnancy,” and “preventing pregnancy” is semantically “contraception,” even though a living human embryo may die in the process.

Keeping in mind the semantic gymnastics above, which are used to avoid raising the issue of embryonic death, one can look at and understand the evolving body of scientific research that attempts to answer the important question of how these drugs and devices prevent a positive pregnancy test. For women concerned about protecting human embryos, fully informed consent prior to the use of particular types of contraceptives requires an explanation of what may happen after fertilization has occurred and the embryo has formed, as well as an estimate of the likelihood of embryo formation and the chances of an embryo’s survival.

— Donna Harrison is a board-certified obstetrician-gynecologist and is the executive director and director of research and public policy for the American Association of Pro-Life Obstetricians and Gynecologists( www.aaplog.org).

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