Risk of pregnancy and external validity in clinical trials of emergency contraception.

OBJECTIVES: To compare women who enroll in emergency contraception (EC) trials to those who decline and to understand why eligible women decline to participate. METHODS: Data were collected from all women seeking EC (n = 5,787) at three clinics in the USA and UK during a period of nearly 1 year (from September 1997 to August 1998). The main outcome measures were pregnancy risk calculated by adjusted cycle day of ovulation. RESULTS: Enrolled and non-enrolled women had similar mean ages and similar mean cycle lengths. However, the enrolled and non-enrolled groups were different with respect to adjusted cycle day of unprotected sexual intercourse (UPSI), the regularity of their cycles, recent hormone use, breastfeeding, the number of other acts of UPSI they had engaged in during the same cycle, and their willingness to participate in the study. Expected pregnancy risk among enrolled patients was higher than among non-enrolled EC seekers (6.5% vs 5.0%, p<0.001, calculated using Dixon conception probabilities, and 5.4% vs 4.6%, p = 0.086, calculated using Trussell conception probabilities). Unwillingness to take part in the study was the most common reason women did not enrol in the trial. Otherwise-eligible women most often declined to enrol because they were concerned about the effectiveness of the trial regimen. CONCLUSIONS: Women in EC trials are likely to face higher pregnancy risk than the general population. Clinical trials might overestimate the number of pregnancies averted by treatment because the number of expected pregnancies in trial populations is not representative of the population of all EC seekers. This information could be useful in projecting the public health impact of expanded EC access.

Opportunistic screening for genital Chlamydia trachomatis infection and partner follow-up in family planning clinics in three Scottish cities.

Three large urban family planning clinics (FPCs) in Scotland participated in a study to examine the implications of opportunistically offering urine testing for genital Chlamydia trachomatis infection and FPC follow-up of positive women and of their male partners. Ninety-eight percent (3029) of women accepted the test. The prevalence of infection was 5.2% and this decreased significantly with age. There was no significant difference in prevalence between centres. Ninety-one percent of positive women intended to inform at least one partner about their infection status. Pretest counselling took about 10 minutes per woman while management (excluding full screening for sexually transmitted infections) of positive women took an additional 10 minutes. Screening in the FPC is acceptable to many women and to some of their male partners. Training and resources for administration and staffing are required if opportunistic screening is to be implemented.