Most everyone agrees that contraceptive barrier methods, from everything from condoms, diaphragms, cervical caps, and spermicide form a chemical or physical barrier that prevents the sperm and egg from coming together. Assuming contraception is effective, a fetus forming or an abortion occurring is essentially impossible.
The great debate then is when other forms of birth control, such as the intrauterine device (IUD) and hormonal contraception (pills, injections, patches) come up.
How do Different Types of Birth Control Work?
When a woman becomes pregnant, first, fertilization happens—the sperm and egg come together. Then implantation occurs—the fertilized egg implants in the womb.
Different groups disagree on whether pregnancy starts with fertilization or implantation. We’ll discuss that in a moment. But first, some background.
Some methods that prevent fertilization but not implantation:
- Natural family planning
- Cervical cap
Different types of birth control target fertilization and implantation in different ways.
- The copper IUD (ParaGard) causes an inflammatory reaction within the female organs and lessens the sperm’s ability to fertilize. However, should fertilization occur, the uterine wall is too irritated to maintain a pregnancy (implantation).
- The hormonal IUD (Mirena) and other forms of hormonal contraception share the following same basic mechanisms of action:
- Prevent ovulation. No egg means no fertilization.
- Thicken the cervical mucus so sperm can’t easily pass into the uterus (thus preventing fertilization).
- Thin the uterine lining. On the chance that ovulation and fertilization do occur, implantation becomes difficult or impossible.
We know how often women get detectably pregnant (with implantation) while on contraception, but we have minimal data on how often these therapies allow for fertilization but not implantation.
A few small studies involving IUDs suggest they work by using both prefertilization and postfertilization methods. A study to evaluate birth control pills and other hormonal forms of contraception is anticipated.
Is Preventing Implantation Abortion?
Many in the medical and scientific communities, including The American College of Obstetricians and Gynecologists, presume that pregnancy begins with implantation. Therefore, they don’t view contraception as abortive.
Organizations that are pro-choice, including Planned Parenthood, agree that pregnancy begins with implantation and that contraception should be encouraged to avoid unintended pregnancy.
Pro-life groups, however, argue that pregnancy begins with fertilization. From that standpoint, preventing implantation of a fertilized egg is abortive.
“We are as much opposed to the birth control pill as to abortion,” says Joe Scheidler, national director of the Pro-Life Action League.
The Christian organization Focus on the Family, which is pro-life, agrees that pregnancy begins with fertilization but is less conclusive about the contraceptive debate.
Its position statement on the topic, last reviewed in 2005, concludes that contraceptives that use only the hormone progesterone (or progestin)
“do not reliably prevent ovulation," which the American College of Obstetricians and Gynecologists agrees.
Focus on the Family concludes that these types of contraceptives are
“problematic for those of us who believe that human life begins at conception.”
However, for injections and pills that contain both progesterone and estrogen:
After two years of extended deliberation and prayer, Focus on the Family’s Physicians Resource Council, has not been able to reach a consensus as to the likelihood, or even the possibility, that these medications might contribute to the loss of human life after fertilization.
The contraception decision is ultimately a personal one. It comes down to your attitudes concerning the definition of pregnancy, your conclusions about the facts, and your own moral and ethical beliefs.