Depo-Provera Users Can
Miss Unplanned Pregnancies

NEW YORK (Reuters Health) - Just a tiny fraction of the women who use the injected hormonal birth-control method called Depo-Provera become pregnant, but many of those who do don't realize they are pregnant until after the first trimester, US researchers report.

In fact, almost one fifth of the women who became pregnant while receiving Depo-Provera received additional injections after they conceived, according to Dr. Lynn Borgatta of Boston University in Massachusetts and her colleagues.

Although the researchers did not discover any abnormalities in the fetuses of women who mistakenly conceived while receiving Depo-Provera, they recommend that women who suspect they may be pregnant to quickly confirm whether or not they have conceived.

"When pregnancy symptoms occur, liberal use of pregnancy testing would provide the women with more options regarding her pregnancy and decrease the rate of re-injection once pregnancy has occurred," Borgatta and her team write in a recent issue of the journal Conception.

Depo-Provera contains a hormone that is similar to the female hormone progesterone naturally produced by the body. The drug interferes with hormonal signaling to keep the ovaries from releasing eggs. It is administered every 3 months in the arm or buttocks to prevent pregnancy.

As part of the study, Borgatta and her colleagues reviewed 402 reports submitted to Planned Parenthood describing women who had conceived while using Depo-Provera between 1994 and 1998. Planned Parenthood centers are required to submit a report for every woman who used their services and became pregnant despite contraception.

Based on the data, the authors estimate that a total of 0.42 pregnancies occur among 1,000 women using Depo-Provera each year. Although the rate of unplanned pregnancy may be low, almost half of the women were diagnosed as pregnant after the first trimester, and almost one fifth received additional contraceptive injections after they had conceived.

The risk of pregnancy is too low to warrant requiring women to submit to pregnancy tests each time they receive additional Depo-Provera injections if they show no signs of having conceived, the authors write. However, they suggested that both health care workers and women remain aware of the risk of pregnancy, even among those who use contraception.

"Clinicians should be aware that pregnancies can occur with proper use of Depo-Provera, and that pregnancy can occur after multiple doses," Borgatta and her team write. "Despite the rarity of pregnancy during use, women using Depo-Provera should be encouraged to report pregnancy symptoms, as they would during use of other long-term methods."

SOURCE: Contraception 2002;66:169-172.

Reference Source 89

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