Hindawi Publishing Corporation Obstetrics and Gynecology International Volume 2012, Article ID 796590, 5 pages doi:10.1155/2012/796590 Review Article Adherence with Drug Therapy in Pregnancy Doreen Matsui Child Health Research Institute, Departments of Pediatrics and Medicine, Children’s Hospital, London Health Sciences Centre, The University of Western Ontario, London, ON, Canada N6C 2V5 Correspondence should be addressed to Doreen Matsui, dmatsui@uwo.ca Received 15 September 2011; Accepted 12 October 2011 Academic Editor: Gideon Koren Copyright © 2012 Doreen Matsui. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Available information suggests that nonadherence with medication is a common problem in pregnant women. Not taking prescribed drugs may have potentially negative consequences as patients may not achieve their therapeutic goal. In addition to the many factors that may inﬂuence medication-taking behaviour in the general population, unique challenges are encountered in pregnant women as both maternal health and fetal well-being must be considered. On the one hand, pregnant women may be motivated to keep their underlying disease under control, while, on the other hand, fear and anxiety regarding the potential harmful eﬀects of their medication on their unborn child may result in poor adherence with needed medication. Providing evidence-based information, ideally preconceptually, regarding the eﬀects of their medication during pregnancy may be important in avoiding misperceptions that lead to nonadherence. 1. Introduction Advances in drug therapy have resulted in eﬃcacious treat- ments being available for many acute and chronic medical conditions; however, it is well recognized that “Drugs don’t work in patients who don’t take them” [1]. The WHO deﬁnes adherence, a term which is often used interchangeably with compliance, as the extent to which a person’s behaviour- taking medication, following a diet, and/or executing lifestyle changes, corresponds with agreed recommendations from a health care provider [2]. Unfortunately, nonadherence with medication regimens is not uncommon with the potential negative consequences of failure to achieve the desired treat- ment goal. Many factors may play a role in whether patients comply with their therapy and pregnancy may present unique challenges as fetal well-being must also be considered in addition to maternal health. This paper will provide a brief overview of medication adherence in general and then will focus on some of the issues related to medication-taking behaviour during pregnancy. 2. Overview of Medication Adherence Nonadherence with drug therapy may take many forms with delayed or omitted doses being the most common errors. Discontinuation of medication administration prior to com- pletion of the course is also common. Adherence is gen- erally measured over a speciﬁed period of time and often reported as the percentage of the prescribed doses of med- ication actually taken by the patient [3]. In a meta-analysis of 569 studies, reported adherence to medical treatment ranged from 4.6% to 100% with a median of 76% and an overall average of 75.2% [4]. Drug compliance may be of particular concern with chronic conditions as therapy is often long term and patients without symptoms may be required to take medication to prevent later complications without any immediate beneﬁts noted. Contrary to what one might think seriousness of the underlying medical condition does not ensure compliance, as has been shown with both cancer and organ transplant therapy [5–9]. Not taking one’s medication is not without clinical implica- tions given the relationship between inadequate adherence and unfavourable disease outcome. In a meta-analysis of 21 studies, good adherence with drug therapy was associ- ated with lower mortality compared with poor adherence (odds ratio 0.56, 95% CI 0.50–0.63) [10]. Other conse- quences of nonadherence may include inappropriate alter- ation in treatment regimens or dosage adjustments with sub- sequent toxicity, unnecessary investigations, and increased costs.