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. Author manuscript; available in PMC: 2014 May 5.
Published in final edited form as: Obstet Gynecol. 2013 Mar;121(3):585–592. doi: 10.1097/AOG.0b013e31828317cc

Table 3.

Failure Rates by Body Mass Index Class

Year 1 Year 2 Year 3
BMI n Rate % 95% CI n Rate % 95% CI n Rate % 95% CI
Lower than 25 48 4.51 (3.4–6.0) 9 6.85 (5.1–9.2) 3 8.44 (6.1, 11.5)
25–30 33 6.63 (4.7–9.4) 5 8.87 (6.3,12.4) 2 11.03 (7.5, 16.0)
30 or higher 18 4.80 (4.0,5.9) 9 7.90 (6.4,9.4) 1 8.92 (7.6, 11.5)
30–40 17 3.69 (2.3, 6.0) 6 7.36 (4.6, 11.6) 1 8.61 (5.3, 13.9)
40 or higher 1 0.53 (0.08, 3.7) 3 10.84 (3.8, 29.1) 0 10.84 (3.8, 29.1)

BMI, body mass index; n, number of failures per BMI class per year; CI, confidence interval.