Contraception
Volume 79, Issue 6 , Pages 424-427, June 2009

Association between efficacy and body weight or body mass index for two low-dose oral contraceptives☆

  • Ronald T. Burkman

      Affiliations

    • Baystate Medical Center, Springfield, MA 01199, USA
    • Corresponding Author InformationCorresponding author. Department of Obstetrics and Gynecology, Baystate Medical Center, 759 Chestnut St., Springfield, MA 01199, USA. Tel.: +1 413 794 5256; fax: +1 413 794 3354.
    • ,
  • Alan C. Fisher

      Affiliations

    • Ortho-McNeil Janssen Scientific Affairs, LLC, Raritan, NJ 08869, USA
    • ,
  • George J. Wan

      Affiliations

    • Ortho-McNeil Janssen Scientific Affairs, LLC, Titusville, NJ 08560, USA
    • ,
  • Christopher E. Barnowski

      Affiliations

    • Johnson & Johnson Regenerative Therapeutics, LLC, Raynham, MA 02767, USA
    • ,
  • Katherine D. LaGuardia

      Affiliations

    • Ortho-McNeil Janssen Scientific Affairs, LLC, Raritan, NJ 08869, USA

Received 26 February 2008; received in revised form 23 December 2008; accepted 23 December 2008. published online 05 March 2009.

Abstract 

Background

This analysis investigated the association of oral contraceptive efficacy with body weight and body mass index (BMI) for hypothesis-generating purposes.

Study Design

Data were from a randomized, parallel-group trial of 180/215/250 mcg of norgestimate (NGM)/25 mcg of ethinyl estradiol (EE) (given to 1671 women) and 1 mg of norethindrone acetate (NETA)/20 mcg of EE (given to 1139 women). Pregnancies were evaluated across BMI deciles and by BMI and body weight dichotomies. A Pearl index was calculated for each treatment group. The relative risk (RR) of pregnancy was calculated with a Cox proportional hazards model.

Results

The Pearl index for women who received NGM/EE was 2.36 [95% confidence interval (CI)=1.33–3.40]; for those who received NETA/EE, the Pearl index was 3.29 (95% CI=1.81–4.77). Consistent, weak positive associations between weight and pregnancy risk were found. Overall, for women with a BMI ≥25 kg/m2 (compared with women with a BMI <25 kg/m2), the RR of pregnancy was 1.84 (95% CI=0.98–3.45); that for women who received NGM/EE was 1.39 (95% CI=0.57–3.40), whereas that for women who received NETA/EE was 2.49 (95% CI=1.01–6.13). For women with a body weight ≥70 kg (compared with women with a body weight <70 kg), the RR was 1.25 (95% CI=0.63–2.46); that for women who received NGM/EE was 1.41 (95% CI=0.56–3.54), whereas that for women who received NETA/EE was 1.12 (95% CI=0.40–3.12).

Conclusion

Women in the higher body weight or BMI category showed a small increase in the risk of pregnancy with these oral contraceptives, but this increase was not statistically significant overall or for either formulation studied.

Keywords: Oral contraceptive, Body weight, Body mass index, Contraceptive efficacy, Low dose

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☆ This study was funded by Ortho-McNeil Janssen Scientific Affairs, LLC, a division of Ortho-McNeil Pharmaceutical (Raritan, NJ, USA).

PII: S0010-7824(09)00028-6

doi:10.1016/j.contraception.2008.12.013

Contraception
Volume 79, Issue 6 , Pages 424-427, June 2009

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