BackgroundCohabitation, referring to a co-residential romantic relationship between two intimate partners without a marriage license, has become widely accepted in contemporary societies. It has been found that cohabitating women have a higher risk of experiencing intimate partner violence (IPV) than married women. However, as yet, no studies have investigated the level and pattern of IPV-associated physical injuries and its mental health impact on cohabitating women. Therefore, we aim to compare IPV-associated physical injuries between cohabitating and married women by conducting a review of 5-year medical records from the emergency departments of two major public hospitals in Hong Kong.MethodsThis is a retrospective cohort study. Using two computerized systems, we identified the medical charts of 1011 women who had experienced IPV and presented at emergency departments between 2010 and 2014, of which, 132 were cohabitating and 833 were married.ResultsCohabitating women were significantly younger (p-value < .0001) and had obtained a higher educational level (p-value = .008) than married women. After adjusting for those two variables, the logistic regression models showed that cohabitating women were approximately 2.1 times more likely than married women to present with head, neck, or facial injuries (OR = 2.1, 95% CI = 1.30–3.40, p = .002), and the risk of having multiple injuries in different locations (head, neck, face, torso, limbs) was almost twice that for cohabitating women compared with married women (OR = 1.82, 95% CI = 1.25–2.65, p = .001). Furthermore, cohabitating women were almost two times as likely as married women to experience more than one method of physical violence (OR = 1.72, 95% CI = 1.18–2.51, p = .005). There were no significant differences regarding mental health, police reporting, and discharge plans.ConclusionsOwing to recent social changes to the family structure, including the growing acceptance of cohabitation, it is essential that a screening program for IPV is established for cohabitating women, as well as the inclusion of IPV content in medical and nursing curriculums and in-service training.