This systematic review critically synthesizes the literature focusing on factors related to preconception health behaviors (PCHBs) among childbearing age women in the United States, developed countries, and developing countries. Ovid Medline and CINAHL databases were searched for peer-reviewed articles published between 1998 and 2008 relating to PCHB. Six major categories of factors were identified: frequency of alcohol intake prior and during pregnancy, glycemic control/diabetes management, physical activity before and during pregnancy, pregnancy planning behavior, cystic fibrosis carrier screening, and other risk factors. A critical finding of this review is that knowledge, awareness, and beliefs of preconception care do not lead to preconception health practice. Younger preconceptional women and women with children were less likely to engage in PCHB. However, women with advanced postgraduate education were more likely to practice preconception care. There is an urgent need to educate young preconceptional women regarding the importance and benefits of practicing preconception care. (Contains 4 tables and 1 figure.)