The 131st Annual Meeting (November 15-19, 2003) of APHA

Abstract #70947

Kelly Blanchard, MSc¹, Charlotte Ellertson, MPA, PhD¹, and Katrina Abuabara². (1) Ibis Reproductive Health, P.O. Box 1985, Parklands 2121, Johannesburg, 10017, South Africa, (2) Regional office for Latin America and the Caribbean, Population Council Mexico, Escondida 110, Col. Villa Coyoacan, Delegacion Coyoacan, Mexico, DF, 04000, Mexico, (52 55) 56598839, kabuabara@popcouncil.org.mx

We compared women who enroll in emergency contraception (EC) trials to those who decline to understand why eligible women declined to participate, and to compare pregnancy risk between these two populations. In this prospective observational study, we collected data on all women seeking EC (n= 5,787) at three clinics during a period of nearly one year. We found that a significant proportion of non-enrolled EC seekers at each site (42-26%) were, according to calculations based on adjusted cycle day of unprotected intercourse and conception probabilities, at no appreciable risk of pregnancy. When expected pregnancy risk was calculated using Dixon conception probabilities, enrolled women were at a significantly higher risk of pregnancy than non-enrolled women (p<0.001). This does not account for the fact that non-enrolled women were also likely at even lower risk that their cycle day of intercourse reflects owing to current or recent hormone use. Otherwise-eligible women most often declined to enroll because they were concerned about the effectiveness of the trial regimen, or because they preferred the standard regimen. We urge caution when extrapolating pregnancy reduction figures from clinical trials to the general population because women enrolling in EC trials may face higher pregnancy risk.

Learning Objectives:

• Describe why eligible women decline to participate in clinical trials of emergency contraception.
• Explain the difference in pregnancy risk between women who participate in clinical trials and those who decline or are ineligible.
• Comment on the implications of external validity bias on efficacy estimates from emergency contraception trials.

Keywords: Contraception, Treatment Efficacy

Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.