- Oral contraceptives work by increasing the level of two hormones in the body: estrogen and progestin (progesterone). The low levels of these hormones in the pill essentially "fool" the body into thinking that it is pregnant and preventing ovulation. They also thicken cervical mucus, which makes it more difficult for sperm to enter the uterus. Although it was once believed that oral contraceptives could prevent a fertilized egg from implanting in the uterus, this does not appear to be the case. Fewer than 1 out of 100 women who take oral contraceptives become pregnant in a year's time, assuming that the pill is taken every day as prescribed. If pills are missed or not taken consistently, the effectiveness is decreased.
- Oral contraceptives are popular because they tend to cause fewer side effects than IUDs and Depo-Provera (the birth control shot). Unlike condoms and diaphragms, they do not interfere with spontaneity during sex. Oral contraceptives also offer some health benefits, including reducing the frequency of acne outbreaks, reducing the chance of developing certain cancers, and reducing the amount of blood lost during menstruation.
- Some women who take oral contraceptives experience side effects, but most of these go away or are improved after taking the pill for 2 or 3 months. The most common side effects include nausea, irregular bleeding, weight gain, reduced sex drive and depressed mood. If side effects are persistent, using a pill with a different ratio of estrogen to progestin, or a different form of progestin, often helps.
- Oral contraceptives are convenient and effective, but like any form of birth control, they do not provide perfect protection from pregnancy. The pill also does not provide any protection from sexually-transmitted diseases, so it is very important to continue to practice safe sex unless you are in a long-term, monogamous relationship. Oral contraceptives, especially the progestin-only type, must be taken consistently to be effective. If you have difficulty remembering to take the pill, another form of birth control may be preferable.
- Oral contraceptives are associated with a condition called DVT, or deep-vein thrombosis. DVT causes blood clots to form, usually in the legs, which can then travel into the lungs, heart, or brain and cause serious problems including heart attack, stroke and pulmonary embolism. The risk of DVT increases with age and is particularly high in smokers. Women who are over 35 years old and who smoke cigarettes should use a different form of birth control.
