Table 1
Hypothetical true association
True maternal BV (Nugent criteria)
Case-control status
Cases (low birth weight)
Controls (normal birth weight)
BV, bacterial vaginosis. “True” odds ratio = (60/140)/(40/160) = 1.71 (95% CI 1.06 to 2.79).
BV
60
40
No BV
140
160
Total
200
200