***TASK***
the task is to simplify the input abstract of a biomedical literature

***INPUT***
the input is the abstract of a biomedical literature

***OUTPUT***
the output is the simplified abstract for the input abstract of a biomedical literature

***DOCUMENTATION***

***EXAMPLES***

Input: Only two trials of limited quality met our inclusion criteria. One study compared two biphasic pills and one triphasic pill, each containing levonorgestrel and ethinyl estradiol. No important differences emerged, and the frequency of discontinuation due to medical problems was similar with all three pills. The other trial compared a biphasic pill containing norethindrone (Ortho 10/11) with a triphasic pill containing levonorgestrel (Triphasil) and with another triphasic containing norethindrone (Ortho 7/7/7). The biphasic pill had inferior cycle control compared with the levonorgestrel triphasic. The odds ratio of cycles with intermenstrual bleeding was 1.70 (95% confidence interval (CI) 1.29 to 2.24) for the biphasic compared with the triphasic levonorgestrel pill. The odds ratio of cycles without withdrawal bleeding was 6.48 (95% CI 3.13 to 13.39). In contrast, cycle control with the biphasic pill was comparable to that of the triphasic containing the same progestin (norethindrone). The available evidence is limited and the internal validity of these trials is questionable. Given the high losses to follow up, these reports may even be considered observational. Given that caveat, the biphasic pill containing norethindrone was associated with inferior cycle control compared with the triphasic pill containing levonorgestrel. The choice of progestin may be more important than the phasic regimen in determining bleeding patterns.
Output:

We did a computer search for studies of birth control pills with two phases versus pills with three phases. We also wrote to researchers and manufacturers to find other trials. We included randomized trials in any language. We found only two trials that looked at two-phase versus three-phase birth control pills. The studies did not have good methods and the authors did not report all their methods. Many women dropped out of the studies, which affects what can be said about the results. One study compared two types of two-phase pills with a three-phase pill. The pills did not differ in any major ways, including the numbers of women who stopped using the pills due to health problems. The other trial compared a two-phase pill with two different three-phase pills. The two-phase pill had worse bleeding patterns than the three-phase pill with a different hormone (levonorgestrel). In contrast, bleeding with the two-phase pill was like that of the three-phase pill with the same hormone (norethindrone). The type of hormone may be more important than the phases for cycle control. These trials did not provide enough evidence to say if three-phase pills worked any better than two-phase types for birth control, bleeding patterns, or staying on the pill. More research would be needed to show whether three-phase pills were better than two-phase pills. However, two-phase pills are not used enough to justify further research.