Impact of bodyweight/body mass index on the effectiveness of emergency contraception with levonorgestrel: a pooled-analysis of three randomized controlled trials

Abstract

Objective:

A pooled analysis of two randomized controlled trials (RCTs) suggested that increased bodyweight and body mass index (BMI) may be associated with a greater probability of pregnancy. To address this issue we investigated whether higher bodyweight and/or BMI negatively impacted the risk of pregnancy in women receiving LNG-EC (levonorgestrel – emergency contraception) after unprotected sexual intercourse in a pooled analysis of three large multinational RCTs conducted by the World Health Organization (WHO).

Methods:

A pooled analysis of three double-blind, multinational RCTs conducted by the WHO to investigate the efficacy of LNG-EC in the general population. All analyses were done on the per-protocol set (PPS) which included 5812 women who received LNG-EC within 72 hours following unprotected sexual intercourse. The analysis was based on logistic regression, with pregnancy as the outcome. BMI and weight were represented in the same model.

Results:

A total of 56 pregnancies were available for analysis in the PPS. Increasing bodyweight and BMI were not correlated with an increased risk of pregnancy in the studied population. A limitation of this study is that despite the large study population in the pooled analysis there were relatively small numbers of women in the high-BMI and high-bodyweight subgroups.

Conclusion:

LNG-EC is effective for preventing pregnancy after unprotected intercourse or contraceptive failure and no evidence was found to support the hypothesis of a loss of EC efficacy in subjects with high BMI or bodyweight. Therefore, access to LNG-EC should not be limited only to women of lower bodyweight or BMI.

Keywords: :

• Body mass
• Bodyweight
• Contraception failure
• Emergency contraception
• Levonorgestrel

Transparency

Declaration of funding

Statistical analysis was funded by Gedeon Richter. The original three studies were conducted by the World Health Organization (WHO) Task Force on Postovulatory Methods for Fertility, and were funded by the UNDP/UNFPA/WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction, WHO. Gedeon Richter Plc donated LNG tablets for these studies, but had no role in the design of the study, data collection, data analysis, data interpretation or the final meta-analysis comprised in this publication.

Author contributions: L.K. contributed to the study protocol development, statistical analysis and drafting of the report. H.v.H. was responsible for organizing the original three RCTs while employed by the WHO and contributed to the drafting of the report. K.G.-D. participated as a member of the WHO task force on postovulatory methods for fertility regulation in the design and conduct of all included trials and in two of the RCTs as a principal investigator. She contributed to the study conception and drafting of the report.

Declaration of financial/other relationships

H.v.H. has disclosed that she was responsible for the trials as an employee of the WHO. K.G.-D. has disclosed that she participated as a PI in two of the trials and was a member of the WHO task force on postovulatory methods for fertility regulation which designed and conducted the trials. K.G.-D., L.K. and H.v.H. have disclosed that they have no significant relationships with or financial interests in any commercial companies related to this study or article.

CMRO peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgments

The authors gratefully acknowledge sharing of the data by the WHO; and also thank Dr Steve Clissold of ContentEdNet for editorial support.