Continuation and Pregnancy Rates Are Similar For Continuous, Cyclic Pill

First published online:

Women are similarly likely to continue taking oral contraceptives and to avoid pregnancy whether they use a continuous regimen or a cyclic regimen of pills, finds a randomized trial conducted in the Dominican Republic.1 A year after starting their assigned pills, about three-fourths of women were still taking them and one in six had become pregnant, outcomes that did not differ between groups. Women’s risk of stopping was elevated if they desired reduced menstruation (hazard ratio, 1.4) and reduced if they had experienced a previous birth (0.5). Bleeding was not significantly associated with the likelihood of stopping.

Although continuous oral contraceptive regimens, which result in less bleeding than do cyclic regimens, have proven effective and acceptable to most women in studies in developed countries, few data are available for developing countries. Investigators conducted the new trial in a reproductive health clinic in Santo Domingo between 2008 and 2010. Women aged 18–30 who requested oral contraceptive pills, whether they were new to contraceptives or switching from a nonhormonal method, were eligible for the study if they had periods lasting 21–35 days, had not breast-fed in the past two months, and were not pregnant or planning to become pregnant in the next 12 months. The women were randomly assigned to take a combined oral contraceptive (norgestrel and ethinyl estradiol), provided for free, according to either a 28-day cyclic regimen or a continuous regimen that did not include any placebos; those in the latter group were allowed flexible breaks (stopping pills for three days) to manage breakthrough bleeding if they experienced persistent bleeding or spotting. At enrollment, women provided information on their demographic characteristics, menstrual patterns and contraceptive use; they provided information on various outcomes (e.g., side effects, discontinuation) at quarterly follow-up visits, and had urine pregnancy tests at months six and 12. The investigators compared characteristics and outcomes between the two groups using bivariate analyses, and assessed independent correlates of the risks of pill discontinuation and pregnancy with multivariate analyses.

On average, the 358 women studied were 23 years old and had two children. Two-thirds were cohabiting with a nonmarital partner. Most had 12 or fewer years of education (88%) and were of mixed race (97%). Although 48% had previously used oral contraceptives, more than two-thirds of this group had used them for a year or less. Nearly all agreed at enrollment that "having a regular menstrual period is a sign of health" (93% in each pill group) and "menstruation is part of what makes me a woman" (90–93%). Only a minority agreed that "stopping menstrual periods is a good idea" (25–29%), but the majority indicated that they "would be interested in not having a period every month" (53–57%) and that they "would be happy to use a birth control method that made my period stop for a certain amount of time" (51–56%).

Analyses showed that women’s probability of still taking their pills at 12 months was 78% in the continuous regimen group and 72% in the cyclic regimen group, a nonsignificant difference. The main reasons women cited for discontinuation were that they had run out of pills or forgotten to take them (cited by 45%) or had experienced side effects other than bleeding (20%). In multivariate analyses, women had a reduced risk of stopping if they had experienced a previous birth (hazard ratio, 0.5), and an elevated risk if they had a desire for reduced menstruation (1.4). Regimen type was not associated with discontinuation. Across all quarterly visits, one-fourth of women in each group reported having missed three or more pills in the past month.

Among all women randomized, the rate of pregnancy at 12 months was 16% in the continuous regimen group and 17% in the cyclic regimen group; again, this difference was nonsignificant. The findings were the same after exclusion of women who had never used their pills, had conceived before randomization or had violated the study eligibility criteria. In multivariate analyses, neither type of regimen nor any of the other characteristics studied significantly predicted pregnancy risk.

Larger proportions of women in the cyclic regimen group than in the continuous regimen group reported any bleeding, regular bleeding or a normal volume of bleeding. Although women using the cyclic regimen were more likely than those using the continuous regimen to perceive their bleeding patterns as acceptable at three months (99% vs. 93%) and at six months (98% vs. 89%), the groups were statistically indistinguishable on this outcome thereafter.

A smaller proportion of women in the continuous regimen group than in the cyclic group reported backache at six months (39% vs. 52%) and breast tenderness at 12 months (29% vs. 42%). The groups did not differ with respect to hemoglobin and hematocrit levels. Two serious adverse events were reported in continuous regimen users and four were reported in cyclic regimen users.

The study’s findings suggest that the continuous and cyclic regimens have similar efficacy, safety and acceptability, although contrary to the investigators’ expectations the former was not associated with better continuation over time. Counseling women about the safety and health benefits of continuous regimens—especially in settings wherein menstruation is viewed as a sign of health and fertility—is important to ensure adherence, they note. "Presenting women with the choice of continuous use as an alternative to cyclic use enables women to select a regimen that works best for their own lifestyle," the investigators conclude.—S. London


1. Nanda K et al., Continuous compared with cyclic use of oral contraceptive pills in the Dominican Republic: a randomized controlled trial, Obstetrics & Gynecology, 2014, 123(5):1012–1022.