| Methods |
Double‐blind, randomized controlled trial. Randomization by a WHO random table. The use of allocation concealment and the method of blinding are not described. We were unable to reach the authors. |
| Participants |
279 women aged 23‐34 years in China. Inclusion criteria were healthy women aged 23 to 34 who have the ability to record menstrual cycle on a diary and have normal physical examination and PAP smear. Exclusion criteria were diabetes mellitus, heart, liver, kidney or nervous system disease, cancer, hypertension, use of hormones 2 months prior to the study, use of injectable contraceptives 6 months prior to the study. |
| Interventions |
Triphasic levonorgestrel/ethinylestradiol (50‐75‐125 μg LNG and 30‐40‐30 μg EE in a 6/5/10 days regimen and 7 days of placebo tablets, N=96) [no brand name described] versus
monophasic levonorgestrel/ethinylestradiol (150 μg LNG and 30 μg EE for 21 days and 7 days of placebo tablets, N=93) [Microgynon] versus
monophasic norethindrone/ethinylestradiol (600 μg NET and 35 μg ethinylestradiol for 21 days and 7 days of placebo tablets, N=90) [Pill No 1]. |
| Outcomes |
Principal outcomes are: pregnancy; side effects; cycle control; discontinuation and reasons for discontinuation. Use of a diary card to collect data on cycle control. Bleeding pattern was analyzed according to the recommendations of Rodriguez 1976. |
| Notes |
The report does not provide an a priori hypothesis or a sample size or power calculation. Study duration: 6 cycles. 17 women in each treatment group discontinued early. The reasons for discontinuation are described. No woman was lost to follow up. One woman in the triphasic group, 2 women in the monophasic levonorgestrel group and one woman in the monophasic norethindrone group were withdrawn because of protocol violations. Analysis not according to intention‐to‐treat principle. The trial was conducted by the World Health Organization. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
No information |
