I am going to try to put in as few words as possible some helpful thoughts on birth control, to add to the discussion taking place, and I am very honored to do so. Many of you will see this as part of Liz Nicholson's blog, which you can access here. I am going to be trying to build off of some of the things that she has said in this discussion.
My wife and I have walked through most of the methods listed below, and have had to at times repent of either our ignorance, or trusting poor information given to us about how these things worked. Often those who work in the offices that prescribe these medications do not have a full understanding of how they work, or a biblical definition of life.
The link that Liz posted to Mark Driscoll's sermon is an excellent discussion of a lot of the theological issues surrounding birth control. You can read the transcript more quickly than listen to the sermon if you are crunched on time, but it is worth a read if these topics have interested you. He deals with a lot of the misconceptions about birth control that people come to by misunderstanding biblical stories like Onan, and commissions like "be fruitful and multiply."
He also deals very effectively with legalism, something that can be at the center of this issue as much as a concern for life. How you plan your family is a very important discussion. It is sinful to be so trite with bringing life into the world that you do not adequately prepare for supporting a child/children once they are here. Check Driscoll's sermon for a helpful discussion of this.
I want to hit quickly on 2 biblical passages that are at the center of this discussion.
1. Psalm 139, among several others like it, speak clearly of life which exists in the womb from the very beginning. The medical community tends to define life at implantation (when the egg has implanted into the uteran wall), versus conception (when an egg has been fertilized). This is not an effective definition logically (simply geography, not substance), or biblically. David writes of God that he "saw" his "unformed substance", and that his "frame was not hidden from You." Much of the Psalm is a declaration of hidden life in the womb. So one of the major questions in birth control is when life begins. Scripture points to this not being a question of trimesters, but from the very beginning.
2. Genesis 3:16. The Lord says to Eve that he will "greatly increase (her/all women's) pains in childbearing." I don't believe that this statement only meant labor pains. Human beings are incredibly inefficient at reproduction, and medical science shows that at least 50% of fertilized eggs (with no interference from BC or otherwise) miscarry. Many are so early that it is not detectable for the mother, others occur later during the process. Too many couples, including my own household have faced the pain of seeing an image with no heartbeat, and wondering what could have been done to prevent it. Feeling the hopelessness of the curse from Genesis 3 in the midst of miscarriages, birth defects, infertility, and on and on the list goes.
*Incidentally, we know that Adam and Eve were not in the garden very long before their sin because Cain is not born until after they were expelled, and there would have been no complications in their fertility before.
Medicinal Birth Control:
Much has been given about NFP (Natural Family Planning), and Liz has written very effectively on that. I would agree with what she has said, but also add a word of warning to those who practice it that they had better be prepared for the possibility of children, since NFP is based on a number of different hormonal signs and circumstances that can vary, be inconsistent, or be unpredictable. For some couples it is easier than others, because some women's bodies are easier to read than others, but to the married couple who cannot support children for any number of reasons, be careful in banking on NFP by itself. Even the average insured couple can plan on paying between 5-15 thousand dollars for a baby just to be born, let alone caring for it and providing for it.
In the rest of the discussion, for the following medicinal forms, the central question is "how do they work?" Within that question, is whether these devices "prevent" conception (fertilization), or whether they are designed to destroy a fertilized egg (these are often referred to as abortifacients).
"The Pill" - Often referred to by simply that name, this is one of the most common forms of medicinal birth controls. The Pill is designed in either pill form, or inserts such as the "Nuva Ring." A certain amount of hormones are released, to essentially fool the woman's body into believing she is pregnant. When her body believes she is pregnant, the hope is that no eggs will be released, and thereby no fertilization will take place. The more research that is done on the pill, the less indictment there seems to be for the pill being abortifacient. That is why I always try to point people towards books like the ones below, done by William Cutrer, a pastor, practicing OBGYN, and Seminary professor. His research is more up to date than men like Alcorn (who I highly respect, though his writing on birth control is often where Christians get their somewhat dated information). The Pill seems to be a question mark at best, and a conscience decision for anyone. It is not a sin issue for someone to take or not take this based on what we know. The Pill is also available in what is called a "progesterone only" form, where the only effects of it are suppressed ovulation (keeping the woman from releasing an egg), and not hardening of the uteran wall.
Intrauterine Devices (IUDs) - An intrauterine device is inserted and meant to be left in for a period of up to (if I remember right) around 3 years. It is sold in the USA under the name "Mirena." The research on IUDs seems to show that what they do is not prevent fertilization (though they sometimes claim to), but rather prevent the egg from attaching. They are very effective at preventing pregnancies (even though they do so unethically) which is why they are growing in popularity in the USA. They have been around for several decades elsewhere in the world. Eggs can still be resilient, and implant in very hostile environments. If an egg implants with an IUD (IUDs still only have somewhere around a 95% success rate at preventing pregnancy) it will be a tubal pregnancy (in the fallopian tubes) which is unsustainable, or a uterine pregnancy which cannot be sustained because of the presence of the IUD. Leaving in, or removing the IUD will destroy the baby.
Morning After Pill - This pill and some others that work similarly are forms of birth control that are given orally after intercourse has taken place. It is intended to flush out any fertilized egg, and is the most blatantly abortifacient form of birth control that there is.
One subject which I have not dealt with are the ethical concerns of different fertility treatments that are out there, which have many similar problems that Christians need to educate themselves on before attempting them as to the positives and negatives of different options. I would refer anyone wanting more information on the ethical questions of the issues surrounding infertility to The Infertility Companion by William Cutrer. Anyone who would like more information on contraception, I would encourage you to check out Cutrer's The Contraception Guidebook. Both are well done and great reads. Sadly there are few well-done and current Christian books on either subject.