BACKGROUND: In the UK, women are recommended to engage with maternity services and establish a plan of care prior to the 12th completed week of pregnancy. The aim of this study was to identify predictors for late initiation of antenatal care within an ethnically diverse cohort in East London. METHODS: Cross-sectional analysis of routinely collected electronic patient record data from Newham University Hospital NHS Trust (NUHT). All women who attended their antenatal booking appointment within NUHT between 1st January 2008 and 24th January 2011 were included in this study. The main outcome measure was late antenatal booking, defined as attendance at the antenatal booking appointment after 12 weeks (+6 days) gestation. Data were analysed using multivariable logistic regression with robust standard errors. RESULTS: Late initiation of antenatal care was independently associated with non-British (White) ethnicity, inability to speak English, and non-UK maternal birthplace in the multivariable model. However, among those women who both spoke English and were born in the UK, the only ethnic group at increased risk of late booking were women who identified as African/Caribbean (aOR: 1.40: 95% CI: 1.11, 1.76) relative to British (White). Other predictors identified include maternal age younger than 20 years (aOR: 1.32; 95% CI: 1.13-1.54), high parity (aOR: 2.09; 95% CI: 1.77-2.46) and living in temporary accommodation (aOR: 1.71; 95% CI: 1.35-2.16). CONCLUSIONS: Socio-cultural factors in addition to poor English ability or assimilation may play an important role in determining early initiation of antenatal care. Future research should focus on effective interventions to encourage and enable these minority groups to engage with the maternity services.