Abstract Objectives To investigate the prevalence of intimate partner violence (IPV) against pregnant women and its relationship with adverse maternal outcomes, including preterm labour, abortion, caesarean section, antenatal hospitalization and vaginal bleeding, in the West Azerbaijan, Iran. Study design Cross-sectional design. Methods In total, 1300 pregnant women, aged 18–39 years, who were referred to hospitals in the Iranian cities of Miandoab and Mahabad in the province of West Azerbaijan in 2009–2010 were recruited for this study by a convenience sampling method. Participants were asked to share their experiences of IPV during pregnancy and adverse maternal outcomes. Results Of these pregnant women, 945 (72.8%) reported that they had experienced IPV during their last pregnancy. A significant association was found between IPV and preterm labour [adjusted odds ratio (adjOR) 1.54, 95% confidence interval (CI) 1.16–2.03], caesarean section (adjOR 11.84, 95% CI 6.37–22.02), antenatal hospitalization (adjOR 6.34, 95% CI 3.82–10.52) and vaginal bleeding (adjOR 1.51, 95% CI 0.9–2.3). Discussion This study demonstrated a high prevalence of IPV during pregnancy, and found that IPV was associated with adverse maternal outcomes including preterm labour, caesarean section, antenatal hospitalization and vaginal bleeding. This adds to the existing literature and can be used to inform healthcare practices in developing countries. Medical, health and surgical services for pregnant women should consider screening for IPV, and providers should be aware that IPV victims are at increased risk for adverse outcomes. Services should also develop links with the Battered Women's Movement; such programmes now exist in many countries.