A Cochrane review «»1 «Edelman A, Micks E, Gallo MF et al. Continuous or ...»1 included 12 studies with a total of 3 628 subjects.
Study findings for combined oral contraceptives (COC) were similar between 28-day and extended cycles in regard to contraceptive efficacy (i.e., pregnancy rates) and safety profiles. When compliance was reported, no difference between 28-day and extended cycles was found. Participants reported high satisfaction with both dosing regimens.
The few studies that reported menstrual symptoms found that the extended cycle group fared better in terms of headaches, genital irritation, tiredness, bloating, and menstrual pain. However, breast tenderness was increased in continuous dosing of the contraceptive patch. 11/12 studies found that bleeding patterns were either equivalent between groups or improved with extended or continuous cycles. Endometrial lining assessments by ultrasound were done in a small number of participants and were all normal.The studies were too small to address efficacy, rare adverse events, and safety.
A safety study «...»2 using the sentinel distributed database of United States assessed the association of continuous/extended use of COC (84/7 or 365/0 days cycles) and venous thromboembolism (VTE). 210 691 initiators of continuous/extended COC and 522 316 initiators of cyclic COC were included. Baseline cardiovascular and metabolic conditions (7.2% vs 4.7%), gynecological conditions (39.7% vs 32.3%), and health services utilization were slightly higher among continuous/extended cyclic than cyclic COC users. Propensity score matching decreased the hazard ratio estimates from 1.84 (95% CI, 1.53 to 2.21) to 1.32 (95% CI, 1.07 to 1.64) for continuous/extended use compared with cyclic COC use. The absolute risk difference (0.27 per 1000 persons) and the incidence rate difference (0.35 cases per 1000 person-years [1.44 vs 1.09 cases per 1000 person-years]) remained low, which may not translate into a clinically significant risk differences between cyclic and noncyclic use.
A survey «...»3 compared extended-cycle use of COC (3 months between periods, n= 260) with women using monthly-cycle COC (n=3616). Women using extended-cycle COC reported significantly higher treatment satisfaction (P = 0.001) and adherence (P = 0.04) and reduced heavy menstrual bleeding (P = 0.029). A non-significant tendency toward reduced menstrual pain (39.5% versus 47.3%) and menstrual cycle-related symptoms (40.0% versus 48.7%) was found in women using extended-cycle vs monthly-cycle COC.
A post hoc analysis «...»4 of a multicenter, open-label, 1-year, phase 3 study of extended-regimen COC with 30 µg EE/150 µg levonorgestrel (LNG) for 84 days and EE 10 µg for 7 days included 799 women. There was a 10% increase in the likelihood of reporting no scheduled bleeding for each additional 91-day cycle completed (OR 1.10, 95% CI 1.01 to 1.21). From the third 91-day cycle, more than one fifth of women reported no scheduled bleeding (third cycle =23%; fourth cycle =22%). There were increases in the likelihood of reporting 0 to ≤6 days vs >6 days of unscheduled bleeding and spotting (OR 1.53, 95% CI 1.39 to 1.68 and OR 1.31, 95% CI 1.21 to 1.42; respectively) for each additional 91-day cycle. By Cycle 2, more than 80% of women reported no unscheduled bleeding or ≤6 days of unscheduled bleeding during each 91-day cycle.