The Île-de-France (IdF) region has a wide range of healthcare services, but maternal mortality there is higher than in other regions of metropolitan France. Previous analyses have shown an increased risk of maternal mortality and a high proportion of suboptimal care among maternal deaths in IdF. Maternal deaths are too rare to analyze the situation at the subregional level. The study of severe maternal morbidity is more suitable for this purpose. The admission of women in the antenatal or postpartum period to intensive care and/or resuscitation units (Usirea) serves as a measure to estimate severe maternal morbidity. The study aims to describe the situation in the Île-de-France health regions by analyzing two categories of events—maternal deaths and stays in Usirea—based on the location of registration and the women’s place of residence. Two permanent databases, the Confidential National Survey on Maternal Mortality (ENCMM) and the Program for the Medicalization of Information Systems (PMSI), were used to compare maternal mortality rates and rates of admission to Usirea across the eight health regions of the Île-de-France region during the 2006–2009 period. The characteristics of women admitted to Usirea and the medical conditions underlying their stays were compared across the regions. Over the study period, depending on the Île-de-France region, admission rates to Usirea at the place of registration ranged from 2.0 (Val-de-Marne) to 8.5 per 1,000 (Paris); rates at the place of residence ranged from 4.2 (Val-de-Marne and Seine-et-Marne) to 4.9 (Paris). The characteristics of women admitted to Usirea differed by region. The medical conditions also showed significant variations depending on whether registered data or residence-based data were analyzed. The characteristics of the populations concerned likely explain part of the differences in maternal mortality and severe morbidity. However, the conditions of availability and access to perinatal and obstetric care are factors that have been little studied, yet likely play a significant role. Specific studies should be conducted by region, taking into account all the characteristics of the women, in order to better understand the disparities presented in this article.