Beginning of each menstrual cycle, estrogen levels begin to rise. Estrogen helps thicken the lining of the uterus to prepare for a fertilized egg. Estrogen levels peak about 14 days into the menstrual cycle, one of the ovaries releases an egg. The release of a monthly egg is called ovulation.

After ovulation, progesterone, another reproductive hormone, begins to rise. Over the next seven days, progesterone further prepares for a fertilized egg. Conception occurs when a fertilized egg implants itself in the uterine lining.

If conception does not occur, both estrogen and progesterone levels drop, signaling the now thickened uterine lining to slough off or shed, and menstruation begins. Birth control pills are nothing more than hormones that contain progesterone and estrogen. They prevent ovulation by maintaining more consistent hormone levels. Without a peak in estrogen, then, the ovary doesn't get the signal to release an egg. No egg means no fertilization or pregnancy. Birth control pills thicken the cervical mucus so the sperm cannot reach the egg, and make the lining of the uterus unreceptive to the implantation of a fertilized egg.

Be cautions if you are taking antibiotics while taking birth control pills, some antibiotics may cause the birth control pills to loose their effectiveness. If you are taking the z-pack, be very cautious because this antibiotic can cause you to become more fertile and may cancel your birth control pills out. I know many women that this has happened to. So be cautious that just because you are on birth control pills does not mean that you can't get pregnant. It is better to play it safe and have two forms of birth control, especially if you are taking antibiotics and relying solely on the "pill". Other drug interactions may include;
Seizure medications: phenytoin, carbamazepine, primidone, ethosuximide, methylphenobarbital, paramethadione, phenobarbital, topiramate, rifampin, griseofulvin, benzodiazepine, Corticosteroids, theophylline, and even St. John's wort.

If you experience any of the following symptoms, call your health care provider immediately and stop the use of the pill;

Abdominal pain

Chest pain (also shortness of breath)

Headaches (especially those that are new, severe, or associated with persistent dizziness, difficulty speaking, fainting,numbness or weakness in extremities

Eye problems (blurred vision or loss of vision)

Severe leg pain (and/or redness and swelling in the calf or thigh)

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