As in many other countries, the number of maternity units has diminished substantially in France, raising concerns about the reduced accessibility of obstetric services. We describe here the impact of closures on distance and mean travel time between pregnant women's homes and maternity units. We used data from the 1998 and 2003 French National Perinatal Surveys and from vital registries to measure indicators of accessibility: straight-line distance to the nearest maternity unit, number of units within a 15-km radius and reported travel time to the unit for delivery. We analyzed these measures for all births, births in rural versus urban areas and according to regional rates of maternity closures. From 1998 to 2003, 20% of maternity units closed (reducing the number from 759 to 621) with regional variations in the rate of closure from 0.0% to 36.0%. Mean distance to the nearest maternity unit increased (6.6-7.2 km, p < 0.001). The proportion of women living more than 30 km from a maternity ward was low; but rose from 1.4% to 1.8%. The number of maternity units with a 15-km radius of the place of residence fell (median, 3 to 2). Differences were more marked in rural areas and in regions highly affected by closures. However, reported travel time did not increase and even declined slightly for women from urban areas and in regions moderately affected by the closures. As such, the closures do not appear to have had a negative impact on the geographic accessibility of maternity units. Pregnant women were faced with a reduction in the number of maternity units near their homes and our results suggest that they more often chose their maternity units based on proximity. A full assessment of the impact of closures on accessibility to obstetric services would require information on how these changes affected available choices for care during pregnancy and delivery.