Background: The use of complementary and alternative medicine has attracted much attention and debate in recent years. The objective of this critical review is to examine the evidence base on use of complementary products and therapies during pregnancy. It examines an important but neglected issue in maternity care. Methods: A database search was conducted in MEDLINE, CINAHL, AMED, and Maternity and Infant Care. A total of 24 papers published between 1999 and 2008 met the selection criteria and were included in the review. Results: Findings of these 24 papers were extracted and reported under four themes: “user prevalence and profile,”“motivation and condition of use,”“perception and self-reported evaluation,” and “referral and information sources.” Conclusions: This review highlights four research gaps in the literature, a lack of: large representative samples; in-depth understanding of user experiences and risk perceptions; research comparing consumption patterns across cultures and over time; and work exploring the nature of the therapeutic encounter with complementary practitioners in this area of women's health care.