Expert: Deborah - 7/29/2008

Question
Through research it has come to my attention that the Pill works by blocking sperm, preventing ovulation, and hardening the uterin wall.  In the event of fertilization the egg cannot attach itself.  My question is how often is a fertilized egg unable to attach?

Answer
Dear Amanda,

Would you share our research with me? From the research I've done, I have drawn a different conclusion.

The pill is not an abortifacient, regardless of how you define pregnancy. It does not interrupt an established pregnancy, i.e. en embryo implanted in a uterus, and it doe not cause fertilized eggs not to implant.

Studies that have shown women on the pill to have a thinner uterine lining than women not on the pill missed an important factor.  That is, it is ovulation which causes the uterine lining to thicken so a fertilized egg can implant.  Women on the pill do not ovulate, so of course there will be no thickening of the lining.  The abortifacient fear is, what if ovulation happens by mistake, and the resulting egg gets fertilized? The answer is, if ovulation occurs, the uterine lining will thicken, then the egg will implant, and a pregnancy will occur.

Here is a list, and how each of them work.
None of these are abortifacient:
Birth Control Pills

There are two types of birth control pills: “combined oral contraceptives” and“minipills.”

Combined oral contraceptives have a combination of two hormones—estrogen and progestin. They work by keeping the ovaries from releasing an egg. The pill must be taken every day.

Minipills contain only one hormone, progestin. They work by thickening the cervical mucus to keep sperm from reaching the egg.

Sometimes they also keep the ovaries from releasing an egg. You must take one pill every day. Minipills are slightly less effective than combined oral contraceptives.
Depo-Provera

Depo-Provera is a form of progestin, similar to the hormone in the minipill. Depo-Provera must be injected with a needle into the woman’s buttocks or arm muscle by a doctor. You must get an injection every three months for the birth control to continue to work.
Norplant

Norplant is a form of progestin that is placed under the skin. Norplant is made of rubber rods that look like matchsticks. A doctor places the rods under the skin of the woman’s upper arm, where they slowly release progestin. A doctor must also remove the rods. There are two types of Norplant. The six-rod Norplant gives birth control for up to five years. The two-rod Norplant gives birth control for up to two years.

There is a new form of Norplant called Implanon, which is supoosed to be even more effective than Norplant.