Obese adolescent girls are more likely to gain weight while using depot medroxyprogesterone contraceptives than those using oral contraceptives or no hormonal contraceptives, researchers report.

Depot medroxyprogesterone (DMPA) contraceptives are given by monthly injections, and are often referred to by one brand name, Depo Provera.

Dr. Andrea E. Bonny of MetroHealth Medical Center, Cleveland, Ohio and colleagues note in the Archives of Pediatrics and Adolescent Medicine that many young women discontinue DMPA contraceptives because they believe the drugs cause weight gain.

While being overweight to begin with has been implicated as a risk for further weight gain, there is little specific information on the subject.

To investigate, the researchers tracked 450 girls ages 12 to 18 years. Of these, 115 started using DMPA, 175 started taking an oral contraceptives and the remaining 160 acted as a comparison “control” group.

Twenty-one percent of the girls had a body mass index of 30 or greater and were classified as obese.

After 18 months, none of the girls on DMPA had become pregnant, compared with 10 percent of those on oral contraceptives and 2 percent of controls.

Among girls who were obese at the start of the study, those on DMPA gained significantly more weight (9.4 kilograms) than did those on oral contraceptives (0.2 kg) or the control subjects (3.1 kg).

Among non-obese girls, weight gains were 4.0 kg in the DMPA group, 2.8 kg among those on oral contraceptives, and 3.5 kg for controls.

The researchers call for further studies on contraception in this age group, concluding that despite its efficacy as a contraceptive method, “the potential contribution of DMPA to severe obesity is concerning.”

SOURCE: Archives of Pediatrics and Adolescent Medicine, January 2006.