sperm e ovum

The “morning-after pill” and how it works

A few weeks ago in Mais Saúde we discussed a recent large study showing that the most effective way to prevent unwanted pregnancy after unprotected sexual intercourse is the IUD.

But by far the most popular form of “emergency contraception” is the so-called “morning-after pill”, which can take several forms, but in Brazil, this pill is made of the semi-synthetic female hormone levonorgestrel (a form of progesterone). This is the same hormone that is used in some daily anti-contraceptive pills, but for emergency contraception, the dose is much higher.

Taken as one or two pills within 3 days of unprotected intercourse (perhaps as much as five days), the pills are almost 90% effective in decreasing the chance of pregnancy, compared with taking no medication after intercourse.

In the United States recently there has been renewed interest about how these pills actually work—how they prevent pregnancy—since some political candidates in this election year have compared using emergency contraception with abortion, a contentious issue no matter where it is discussed.

Surprisingly perhaps, it is interesting that scientists are still not sure how these pills work, because to study the effects in humans would mean disrupting the reproductive system of an individual, so the best we have in several theories. It was originally thought that the pills prevent the implantation of a fertilized egg in the uterus, and some anti-abortion activists have equated this with abortion, but more recent studies indicate this mechanism of action is unlikely.

The best data now shows that the morning-after pill works by suppressing the release of eggs from the ovary. The body, upon receiving the high dose of levonorgestrel, is basically tricked into believing the individual is already pregnant, so the ovary does not release a new egg. Without a released egg, even with millions of sperm ready to work, there is no fertilization and no embryo. If this is the mechanism, in no way can this be considered abortion. It is possible that in some cases the medication work through other mechanism, such as making the cervical mucous inhospitable for the sperm, but again, it is very difficult to study this in the reproductive system of human beings.

To summarize, it appears the morning after pill does not in any way cause an abortion of an embryo. The pill is highly effective but not perfect. If used, it is more effective the sooner taken after unprotected sex. It is not a method for daily birth control, like the IUD, which provides both daily contraception as well as emergency contraception if needed. Finally, none of these methods provides any protection from AIDS or STDs. Safe sex should always be practiced.

You may wish to discuss the various contraceptive methods with an obstetrician or gynecologist. If you need to find one, you can do so through our main website: www.procuramed.com. This service is fast, easy, and without cost.

Esta postagem também está disponível em: Portuguese (Brazil)