A woman taking contraceptive precautions may become pregnant for a variety of reasons. Understanding the causes of failure can help those steps needed to prevent an unwanted pregnancy.


Reasons related to sexual activity:

(1) The woman was not abstinent and was not using a contraceptive method.

(2) The woman engaged in unexpected sexual activity (either no contraceptive method used, or one was misused).


Reasons related to birth control method:

(1) Use of a birth control method that is not effective (ineffective or suboptimal).

(2) Failure to use birth control every time sexual intercourse occurs or missing doses of an oral contraceptive regimen.

(3) Failure to use birth control method correctly (failure to use spermicide cream when needed; failure to place a diaphragm correctly).

(4) Failure of birth control method (hole in a condom, drug interference with oral contraceptives, etc).



• Drugs may induce the metabolism of oral contraceptive agents or decrease their effectiveness. These include many antibiotics and several anti-epileptic drugs.


Male partner related:

(1) Failing to wait for aspermia following a vasectomy.

(2) Lying about having had a vasectomy.


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