Contraceptive failure and the progestogen-only pill.

Contraceptive failure and the progestogen-only pill The case report by Chandler and Nash1 in this issue of the Journal is interesting and highlights the need for trials of hormonal contraceptive use to include obese women. The authors acknowledge that despite an apparent association between contraceptive failure and higher body weight in studies of a Norplant® prototype and a levonorgestrelreleasing vaginal ring, there is insufficient evidence to demonstrate reduced efficacy in heavier women using the progestogen-only pill (POP). Current guidance from the Faculty of Sexual and Reproductive Healthcare (FSRH)2 advises one progestogen-only pill (POP) per day irrespective of body weight. This recommendation is based on the evidence available at the time of publication and the consensus of the guideline development group. The recent review of obesity and oral contraceptive pill (OCP) failure by Trussell et al.3 lends further support to FSRH guidance. The authors conclude that they “found no convincing evidence that very heavy or obese women have a higher risk of oral contraceptive pill [combined and progestogen-only] failure during perfect use than thinner women, even with the lowest doses formulations”. Trussell and colleagues mention the difficulties of reliably measuring adherence and they speculate that OCs may be less forgiving of imperfect use among heavier women. Given that long-acting reversible methods of contraception (LARC) are known to be highly effective and less dependent on adherence than OCs, LARC methods should be offered to all women, particularly following OCP failure.