Linda S. Potter

How effective are contraceptives ? The determination and measurement of pregnancy rates

Objectives To provide an overview of contraceptive effectiveness and its determinants as well as reasons for the gap between the actual and expected number of unplanned pregnancies for various categories of users; to provide some guidelines for more precise, consistent terminology and measurements for use in future research; and to provide specific counseling guidelines; using combined oral contraceptives (OCs) as the example. Data Sources Fifty-three articles on contraceptive effectiveness were reviewed, with a particular focus on pregnancy rates among OC users and the quality of use contributing to those rates. Definitions and measurement of contraceptive effectiveness, its components, and its determinants were examined and discrepancies explored. Methods of Study Selection Papers discussed were selected because they had special relevance. Only a few of the papers discussed in this article were quantitative studies of contraceptive behavior and effectiveness. Others were review articles, discussions of the appropriate measurement of various components of effectiveness. Others provided conceptual frameworks for studying method effectiveness. All published studies of OC compliance were reviewed. Tabulation, Integration, and Results Comparing the definitions and measurement of both compliance and effectiveness revealed important inconsistencies. However, some trends did emerge, and these papers did provide a framework for the following discussion. The findings were used to develop a more coherent set of definitions, measurement approaches, and counseling strategies. Characteristics of the user, the method, and the service delivery system all play a role in contraceptive effectiveness. However, it is the quality of use, ie, the users own behavior, that is the immediate determinant of the effectiveness of any short-term contraceptive method. The mean pregnancy rate for better-than-average users is 4%; for poorer-than-average users, it is 8%. Conclusions The range of contraceptive effectiveness rates is closely associated with user characteristics. Oral contraceptive users need to know that their own chance of becoming pregnant will vary with their fecundability, when and how frequently they have sexual intercourse, and, especially, how consistently and correctly they take their pills. The likelihood that any one user will take OCs correctly and consistently also is associated with her life-style, socioeconomic status, age, and other factors. Further research is needed to determine how forgiving OCs are of various pill-taking errors, to determine the impact of dual method use (eg, OCs and condoms), and to assess the effects of user, method, and programmatic characteristics on correct and consistent use and, in turn, on effectiveness.

Progestin-only oral contraception: A comprehensive review: VI. Cardiovascular disease

In order to provide information for the appropriate package insert labeling of progestin-only oral contraceptives (POC) in the US, a comprehensive review was made of norgestrel (0.075 mg) and norethindrone (0.35 mg), with the clinical differences indicated where applicable. The goal of this review was to cite primary sources for virtually all research specific to POPs since 1975. Conclusions and the types of studies which support these conclusions are given for each major section. The introductory chapter discusses the advantages and disadvantages of POCs and the magnitude and prevalence of their use. Future trends are also predicted. Chapter 2 considers the mode of action, including ovulation prevention; suppression of midcycle gonadotropin peaks; changes in cervical mucus, the endometrium, and the fallopian tubes; and clinical implications. Chapter 3 covers pharmacology (pharmacokinetics, pharmacodynamics and potency, and clinical implications). The next chapter presents information on efficacy and pregnancy outcomes in terms of pregnancy rates, compliance and efficacy, ectopic pregnancies, the outcome of pregnancies conceived while using POCs, and fertility following discontinuation. Chapter 5 focuses on metabolic effects, specifically lipid metabolism, carbohydrate metabolism and diabetes, coagulation factors, and blood pressure. Cardiovascular disease is considered in the next chapter, and chapter 7 presents findings on endometrial, ovarian, cervical, breast, and other cancers. A host of other medical considerations are discussed in chapter 8, including persistent ovarian follicles; reproductive tract infections; abnormal vaginal bleeding; uterine fibroids; gestational trophoblastic disease; benign breast disease; diseases of the liver, gallbladder, and bowel; endocrine dysfunction; epilepsy; bone density; sickle cell disease; ocular effects; surgery; and overdose. The last 4 chapters cover interactions with drugs and laboratory tests, common side effects, breast feeding, and effective use of POCs. Information on precautions and contraindications, indications, use instructions, and instructions for appropriate actions after missing a pill is appended.