Comparison 4. 20 ug ethinyl estradiol and 100 ug levonorgestrel, 28‐day versus 168‐day cycles for 6 months.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4.1 Overall discontinuation	1	32	Peto Odds Ratio (Peto, Fixed, 95% CI)	0.33 [0.04, 2.60]
4.2 Discontinuation for bleeding reasons	1	32	Peto Odds Ratio (Peto, Fixed, 95% CI)	7.39 [0.15, 372.38]
4.3 Pregnancy	1	32	Peto Odds Ratio (Peto, Fixed, 95% CI)	Not estimable
4.4 Mean of total bleeding days (bleeding + spotting) in first trimester (84 days)	1	28	Mean Difference (IV, Fixed, 95% CI)	‐4.33 [‐12.27, 3.61]
4.5 Mean of total bleeding days (bleeding + spotting) in second trimester (84 days)	1	27	Mean Difference (IV, Fixed, 95% CI)	‐3.90 [‐15.66, 7.86]
4.6 Mean spotting days in the first trimester (84 days)	1	28	Mean Difference (IV, Fixed, 95% CI)	3.55 [‐1.71, 8.81]
4.7 Mean spotting days in second trimester (84 days)	1	27	Mean Difference (IV, Fixed, 95% CI)	4.82 [‐5.76, 15.40]
4.8 Mean bleeding days in first trimester (84 days)	1	28	Mean Difference (IV, Fixed, 95% CI)	‐7.73 [‐13.97, ‐1.49]
4.9 Mean bleeding days in second trimester (84 days)	1	27	Mean Difference (IV, Fixed, 95% CI)	‐8.86 [‐12.82, ‐4.90]
4.10 Symptoms: total number of bloating days	1	27	Mean Difference (IV, Fixed, 95% CI)	‐10.99 [‐19.77, ‐2.21]
4.11 Symptoms: total number of "menstrual pain" days	1	27	Mean Difference (IV, Fixed, 95% CI)	‐11.45 [‐18.40, ‐4.50]