Background The cost of maternity care can be a barrier to access that may increase maternal and neonatal mortality risk. We analyzed spending on maternity care in urban slum communities in Mumbai to better understand the equity of spending and the impact of spending on household poverty. Methods We used expenditure data for maternal and neonatal care, collected during post-partum interviews. Interviews were conducted in 2005-2006, with a sample of 1200 slum residents in Mumbai (India). We analysed expenditure by socio-economic status (SES), calculating a Kakwani Index for a range of spending categories. We also calculated catastrophic health spending both with and without adjustment for coping strategies. This identified the level of catastrophic payments incurred by a household and the prevalence of catastrophic payments in this population. The analysis also gave an understanding of the protection from medical poverty afforded by coping strategies (for example saving and borrowing). Results A high proportion of respondents spent catastrophically on care. Lower SES was associated with a higher proportion of informal payments. Indirect health expenditure was found to be (weakly) regressive as the poorest were more likely to use wage income to meet health expenses, while the less poor were more likely to use savings. Overall, the incidence of catastrophic maternity expenditure was 41%, or 15% when controlling for coping strategies. We found no significant difference in the incidence of catastrophic spending across wealth quintiles, nor could we conclude that total expenditure is regressive. Conclusions High expenditure as a proportion of household resources should alert policymakers to the burden of maternal spending in this context. Differences in informal payments, significantly regressive indirect spending and the use of savings versus wages to finance spending, all highlight the heavier burden borne by the most poor. If a policy objective is to increase institutional deliveries without forcing households deeper into poverty, these inequities will need to be addressed. Reducing out-of-pocket payments and better regulating informal payments should have direct benefits for the most poor. Alternatively, targeted schemes aimed at assisting the most poor in coping with maternal spending (including indirect spending) could reduce the household impact of high costs.