A Cochrane review included 5 studies with a total of 2427 subjects. One study compared two immediate-start methods. Of the four trials comparing immediate start with conventional start, one focused on the skin patch and another on depot medroxyprogesterone acetate (with or without a bridge method). The remaining two trials studied oral contraceptives (Ocs), but one examined the same combined OC with different initiation methods, while the other left the OC choice to clinicians. No study was adequately powered for contraceptive effectiveness (pregnancy rate). Method discontinuation was similar between groups in all trials. Bleeding patterns and side effects were similar in trials that compared immediate with conventional start.
Comment: The quality of evidence is downgraded by study quality (various limitations), downgraded by inconsistency (heterogeneity in interventions), and by imprecise results (limited study size for each comparison).