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Predict later weight gain for teens taking DMPA?
By Jeffrey T. Jensen, MD, MPH, Editor, OB-GYN Clinical Alert, Leon Speroff Professor and Vice Chair for Research, Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland,
Source: Bonny AE, Secic M, Cromer B. Early weight gain related to later weight gain in adolescents on depot medroxyprogesterone acetate. Obstet Gynecol 2011; 117:793-797.
The investigators prospectively enrolled and followed a cohort of 97 teens before and six, 12, and 18 months after starting DMPA. They examined whether early weight gain observed among adolescents initiating contraception with DMPA predicts continued excessive weight gain and evaluated the risk factors for excessive weight gain. The entire study population was categorized into two groups based upon weight gain observed at six months; excessive early weight gain was defined as a gain of more than 5% of starting body weight. Excessive early weight gain was seen in 20 patients, and the remainder of the cohort (77 patients) gained 5% or less of their starting weight. Excessive early weight gain (> 5%) at six months was correlated with a higher BMI at 12 and 18 months. Although the mean BMI was not significantly different between the two groups at baseline, and both groups showed an increase in BMI at 12 and 18 months, the excessive early weight gain group demonstrated a greater and excessive increase at all time points such that the differences between groups became significant. Furthermore, the mean BMI in the excessive weight gain group moved into the obese range by the end of study. The authors concluded that teens who experience more than a 5% weight gain after six months of DMPA use are at risk for continued excessive weight gain with continuing use of the method. They suggest that a six-month checkup be used to identify adolescents at risk for continued excessive weight gain and to counsel them about contraceptive options.
Weight gain has been reported in more than half of adolescents receiving DMPA and is cited as the primary reason for method discontinuation by more than 41% of adolescents who use the method.1,2
The recently published manuscript from Bonny et al represents a secondary analysis of data from a two-year prospective study of bone density and hormonal contraception.3,4 The study population consisted of post-menarche females aged 12 to 18 years attending one of four urban adolescent health clinics in Cleveland. The current analyses include only those subjects who selected DMPA for contraception. All of these subjects also participated in a randomized trial evaluating an intervention for unscheduled bleeding and received adjunctive estradiol cypionate or placebo. Girls with a body weight that exceeded 250 pounds were excluded from the study.
The authors based the decision to define weight gain in the first six months of use as excessive when it exceeded 5% of the baseline weight on findings by Le and colleagues.5 These investigators found in a study of women 16–33 years, those who gained more than 5% of their body weight within six months of DMPA initiation were at risk for future weight gain with the method. Although using this criterion, the study cohort in the Bonny paper was not dichotomized until six months; there were no significant differences in the baseline characteristics between the groups. In other words, in contrast to prior studies, race (more than 60% were African American), age, physical activity, age, or baseline BMI (more than 35% obese) did not predict weight gain at six months. A multivariant analysis confirmed this lack of association.
However, after six months of use, we can begin to make predications. At this time, a group of users at risk for significant and clinically important weight gain emerges. The screening test is simple; weigh your patient and compare the change in weight over six months as a percentage of the initial weight. If this exceeds 5%, your patient is at risk for excessive weight gain.
Since we can't make assumptions about which teens will develop unacceptable weight gain after starting DMPA, the method should be in the portfolio that we discuss with teens that present for contraceptive counseling. DMPA is a highly effective and well-tolerated, reversible method. Unfortunately, rates of discontinuation are high. Concerns about weight gain and other side effects can prevent an teen from returning for a repeat injection. But the data suggest that this side effect should not be a worry for most users. Almost 80% of the population in the Bonny study did not experience excessive weight gain at six months.