20 mcg versus >20 mcg estrogen combined oral contraceptives for contraception
Evidence Summaries Level of Evidence = B
Combined oral contraceptives with 20 mcg estrogen appear to have similar efficacy as those with >20 mcg estrogen. Bleeding pattern disruption are more common with low-dose estrogen.
A Cochrane review 1 included 21 studies. English-language reports of randomized controlled trials that compare a COC containing 20 mcg EE with a COC containing >20 mcg EE were eligible. No differences were found in contraceptive effectiveness for the 13 COC pairs for which this outcome was reported. Several COCs containing 20 mcg EE resulted in higher rates of early trial discontinuation (overall and due to adverse events such as irregular bleeding) as well as increased risk of bleeding disturbances (both amenorrhea/infrequent bleeding and irregular, prolonged, frequent bleeding, or breakthrough bleeding or spotting) than their higher-estrogen comparison pills.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment, lack of blinding, and more than 20% loss to follow up).
1. Gallo MF, Nanda K, Grimes DA, Lopez LM, Schulz KF. 20 µg versus >20 µg estrogen combined oral contraceptives for contraception. Cochrane Database Syst Rev 2011;(1):CD003989 [Assessed as up-to-date: 15 JUL 2013]. [PMID:21249657].
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