Table 2

Results of included studies reporting unintended pregnancy and pregnancy (intention undefined) in ascending order of incidence

StudyIncidence rate (per 100 person-years)95% CIPerson-years of exposureDuration (months)Measurement of pregnancyFrequency of measurementQuality (%)
Unintended pregnancy
et al 77
7.24.5 to 10.9305.412Urine testMonthly40
et al 44
11.89.7 to 14.579630Urine testQuarterly on suspicion only53
et al 42
13.46.1 to 25.467.224Urine testQuarterly20
et al 40
20.74.3 to 60.514.51Urine testWeekly27
et al 32
26.321.9 to 30.7528.524Serum test6 monthly for 1 year+1 measurement in second year60
et al 33
27.323.3 to 31.7615.618Test (unspecified)6 monthly67
et al 34
28.022.6 to 34.3335.812Urine testQuarterly60
et al 46
51.744.9 to 59.340012Urine testMonthly40
et al 39
53.021.0 to 110.013.22Urine testMonthly40
et al 41
59.641.7 to 82.560.44Urine testMonthly40
Pregnancy (intention undefined)
et al 51
2.01.4 to 2.91619.624Self-reportQuarterly on suspicion only21
et al 37
2.72.1 to 3.52259.315-year open cohort * Urine testMonthly on suspicion only21
et al 54
3.31.4 to 5.2359.624Self-report6 monthly43
et al 43
5.94.1 to 8.4540.112Self-report4 monthly36
 van Loggerenberg
et al 52
8.55.6 to 11.5376.524Urine testMonthly on suspicion only36
 Van Damme
et al 48
8.66.7 to 10.8837.5≤24* Urine testQuarterly29
et al 50
12.69.7 to 16.1500.824Urine testQuarterly on suspicion only50
et al 47
13.511.3 to 16.1968.0≤48* N/AN/A21
et al 56
14.27.6 to 24.391.56Urine testQuarterly36
et al 49
14.512.0 to 17.5784.048Urine testQuarterly43
et al 53
15.210.4 to 21.5210.36Self-reportQuarterly71
et al 36
15.813.0 to 19.0721.0 42Urine testN/A43
et al 93
18.316.2 to 20.61467.0≥24* Urine testN/A50
 Page et al 38 22.016.3 to 30.1186.412Self-reportQuarterly50
et al 35
23.420.6 to 26.51067.518Urine test6 monthly on suspicion only43
  • *Duration varied for different participants.

  • †Person-time estimated by: (n_FSWs * yrs * retention) − (n_preg * yrs/2); where: n_FSWs, number of FSWs enrolled; yrs, study duration in years; retention, retention  rate; n_p reg, number of women who became pregnant. We could not use the approach advocated by Vandenbrou c ke et al 95 as average follow-up time among FSWs was not known.

  • FSWs, female sex workers; N/A, not measured or reported, data not available from author.