Signs of Pregnancy While on the Pill

The term “the pill” encompasses various oral contraceptives. Estrogen-progestin or combined pills suppress the ovaries' monthly release of an egg cell. While progestin-only pills also work this way, they mostly thicken cervical mucus, inhibiting sperm movement. Although they make unplanned pregnancy quite unlikely, oral contraceptives are not perfectly effective at preventing it. You should bring any questions or concerns about your own situation to your health care provider's attention.

Effectiveness Rates

Every pregnancy prevention method has two different effectiveness rates: one for correct, consistent use and one for common use, or actual practice. Combined oral contraceptives are over 99 percent effective in correct and consistent use and 92 percent effective in common use, according to "Family Planning: A Global Handbook for Providers." Used correctly and consistently, progestin-only pills are over 99 percent effective. In common use, they are 99 percent effective for breastfeeding women, and 90 percent to 97 percent effective for non-breastfeeding women.

Effectiveness-Boosting Behaviors

Taking the correct pill in the sequence every day at the same time will boost your odds of preventing pregnancy. Connect your pill-taking to a daily activity if this helps you remember it. Always make sure you have your next pack of pills before you need to start it.

Preferably before any problem arises, ask your health care provider what directions to follow if you forget to take any pills or take them late. Also ask your provider for guidance if you have severe diarrhea or vomiting; are switching methods; have just had a miscarriage or abortion; have just given birth; are breastfeeding; or take any medications that could make your contraceptive pills less effective, such as cyclophosphamide, certain anti-fungus drugs, certain antibiotics and particular anti-seizure medications. In any of these situations, you may need a temporary backup birth control method such as condoms or nonpenetrative sex.

Possible Pregnancy Symptoms

The most common symptoms of pregnancy are late, missed, or lighter than normal periods, nausea, breast swelling or tenderness, headaches, fatigue, darkened nipples, backaches and increased urination, according to the American Pregnancy Association. Yet the side effects of oral contraceptives also include differences in menstruation, nausea, breast tenderness and headaches.

To find out whether pregnancy, your pills or something else may be causing your symptoms, seek a doctor's help. Your doctor may perform urine and blood tests, a physical examination and/or an ultrasound to determine whether or not you are pregnant and if so, how far along you are. Even if you have taken a home pregnancy test, you will benefit from medical follow-up, whether your result was positive or negative.

Consequences for the Fetus

If you are indeed pregnant, by the time you find out, your fetus' major organ systems may already be formed. You may worry that your oral contraceptives have hurt your baby's development. Whatever medications she has or has not taken, no pregnant woman can absolutely guarantee that her child will not have disabilities. According to Family Health International and the manual "Family Planning: A Global Handbook for Providers," oral contraceptives, whether combined or progestin-only, do not cause prenatal impairments or other harm.