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Birth control pills
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Birth control pill -- effective in first month?
Originally Published: April 11, 1997
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What are the statistics for birth control pill failure in the first month that you start taking it?
Alice cannot provide you with any exact statistics on first month birth control pill failure rates. She can, however, tell you that your first packet of birth control pills may not provide you with the same level of protection against pregnancy as the following months' pill packets will (assuming they are taken correctly). The reason for this possible decreased effectiveness of the pill during the first few weeks you take it lies in the chance of an egg being released before you take the first pill. Most birth control pills rely on the action of the hormone, estrogen, which essentially inhibits the release of an egg from the ovary. Combination pills that contain estrogen and progestin (a synthetic version of the hormone, progesterone) might provide a little more protection in the first few weeks. This is because progestin works a little differently than estrogen. It is believed that progestin decreases the ability of sperm to penetrate the cervical mucus (in order to swim through the uterus and fallopian tubes to fertilize an egg), and prevents the lining of the uterus from developing normally so that a fertilized egg would find it difficult to implant in the uterus. If you'd like to learn more on how birth control pills work, check out How do birth control pills work? in Alice's Sexual Health archives. Regardless of the type of birth control pill you are taking, it is always recommended to use a back-up method of birth control, such as a condom, diaphragm, or cervical cap, until you've completed your first pill packet. It's also a good idea to keep a back-up method of birth control on hand in the event you've forgotten to take your pills and you want to have sex, or if you're taking antibiotics that might lower the effectiveness of the Pill (see Tetracycline and the pill in Alice's Sexual Health archives).
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