Comparison of Serum Contraceptive Hormone Levels Between Normal Weight and Obese Users of the NuvaRing®
Comparison of Serum Contraceptive Hormone Levels Between Normal Weight and Obese Users of the NuvaRing®
There are over 60 million women of reproductive age in the U.S. and a majority of these women
 qualify as overweight or obese. Evidence suggests that there is an association between
 increased body weight and decreased contraceptive efficacy. Studies with the combined
 hormonal contraceptive patch (Evra®) and the subdermal contraceptive implant (Norplant®)
 demonstrate higher failure rates in heavier versus lighter women.

 Weight related differences in the effectiveness of NuvaRing® need further study. A single
 secondary analysis of pooled data from Phase III clinical trials of NuvaRing® noted no
 difference in pregnancy rates among women in the highest weight decile (>166#) versus the
 rest of the study population using the ring. (Westhoff, 2005) The finding of no difference,
 however, was influenced by too few obese subjects in the analysis which contributed to wide
 confidence limits. Additional studies are needed to explore how well the contraceptive ring
 functions to maintain effective serum steroid concentrations to suppress ovarian activity in
 obese women.

 This investigation focused on evaluating mean serum concentrations of hormones released in
 obese and normal weight women using the NuvaRing® . This study was a prospective clinical
 trial. Normal weight women are defined as women with a BMI 19-24.9 and obese women are those
 with a BMI 30-39.9. We recruited forty adult women interested in initiating the combined
 hormonal contraceptive ring to two months of use to complete analysis of at least 34 subjects
 (17 normal weight, 17 obese). We compared mean serum concentrations of ethinyl estradiol (E2)
 and etonogestrel (ENG) along with additional markers for ovarian suppression. These markers
 included sonographic evidence of follicular development and ovulation as well as circulating
 E2 levels which strongly correlate with follicular development and endometrial proliferation
 during the second month of NuvaRing® use. Assessment of these parameters will translated to
 understanding contraceptive-mediated suppression of ovarian function in these two groups.
 Subjects also logged patterns of ring use and bleeding patterns during the study period.
Inclusion Criteria:

 -  18-35 yo

 -  Meet BMI requirements

 -  Weight stable

 -  English speaking

 -  Desire contraception

 -  History of regular menses with normal uterus and ovaries

 -  Medically eligible for combined hormonal contraception

 -  Tolerates phlebotomy/TVS

 Exclusion Criteria:

 -  Exclusion:

 -  Heavy smokers

 -  Users of medications that alter hormone levels