It always surprises me how little people know about the medications they are taking. They don't know the names, they don't know what's in them, and they don't know how they work. This is especially true of contraceptives.
I'm not going to get into whether or not birth control is "right". That's a whole other can of worms. I will say, though, that it's shameful for a doctor or midwife to write a prescription for a woman without going over the basic info of the drug or instrument they are prescribing. By the same token, it's irresponsible of a woman to accept or take the meds without asking questions, or at the very least reading the fine print and educating herself (guilty as charged).
So, here's a link about hormonal contraceptives http://www.contracept.org/hormonal.php
Basically, here's a run-down:
"How Hormonal Methods Work
All hormonal contraceptives have at least three mechanisms of action. Artificial female hormones are the active ingredient in all hormonal contraceptives — estrogen and progestin. Some products contain both hormones and others progestin only. Using both hormones together is somewhat more effective than progestin alone, but the estrogen component is responsible for most of the serious health hazards associated with hormonal methods.
Hormonal contraceptives prevent ovulation. No egg is released so sperm cannot fertilize it. It is widely agreed that this is a major mechanism of hormonal birth control.
A woman may ovulate anyway. Hormonal contraceptives may also prevent fertilization by changing the consistency of natural secretions in the vagina, making it harder for the sperm to reach the egg. It is not clear how effective this mechanism is in preventing fertilization.
A woman may ovulate anyway, and sperm may still reach the egg, resulting in fertilization. When this occurs, hormonal contraceptives make it difficult for the embryo to implant in the uterus by keeping the edometrium (lining of the uterus) thinned. This results in the death and expulsion of the embryo. Most scientists agree this occurs, but it is not clear how often. Some doctors do not prescribe hormonal contraceptives because they find this mechanism objectionable. [more about this...] "
For IUDs: http://www.contracept.org/iud.php
"Hormonal IUDs: Hormonal IUDs prevent pregnancy by releasing the hormone progestin, which thickens the cervical mucus, acting as a barrier to prevent sperm from entering the uterus. This type of IUD also affects the lining of the uterus to prevent a fertilized egg from being implanted, should fertilization occur. Progestasert IUD must be replaced every 8-24 months. Since this IUD was discontinued in 2001, any woman who had one implanted should have had it removed by now. The Mirena IUS is the next generation of hormonal IUDs and can be used for up to five years. More about the Mirena IUS...
Non-hormonal IUDs: For copper IUDs, the metal itself seems to exert a spermicidal effect. The copper also affects the lining of the uterus by not allowing a fertilized egg to implant, and it stimulates the production of prostaglandins, chemicals that affect the hormones needed to support a pregnancy. ParaGard is a long-term IUD that may be left in place for ten years. More about the ParaGard Copper IUD... "
So, women, ask questions! Get educated! It's not presumptious to ask your health care provider to sit down and talk for a few minutes. If they don't have time or answers for you, then look elsewhere. A pharmacist is usually much better prepared to answer questions on drugs, and it's their job to take that extra time to discuss it with you.
As for contraceptives, in the end, it comes down to this - when does life begin? If you believe, as I do, that it begins at conception, then this is a good time to evaluate what birth control you are using. Educate yourselves!