This cross-sectional study was carried out to assess the association between consanguineous marriages and adverse pregnancy outcome in the north of Jordan. Women delivered in four major hospitals in the north of Jordan between April 2007 and May 2007 were included in the study. Non-Jordanian women and women with multiple pregnancies were excluded. Mothers answered a pilot-tested structured questionnaire administered by trained personnel in the maternity ward. Data regarding pregnancy outcomes were obtained from the patients' individual records. A total of 3,269 women with a mean age of 27.2 (SD 6.6) years were included. About 49% of women had consanguineous marriages. Consanguineous marriages were significantly associated with low birth weight delivery (13.9% vs. 10.1%), preterm delivery (19.9% vs. 12.3%), and births with congenital anomalies (4.1% vs. 0.8%) compared with non-consanguineous marriages. In the multivariate analysis, consanguinity was significantly associated with preterm delivery (OR = 1.5, 95% CI 1.2, 1.9), and congenital malformations (OR = 6.5, 95% CI 2.8, 15.3). In conclusions, this study supports the association between consanguinity and some adverse pregnancy outcomes.