In the Île-de-France region, the rate of labour force participation among mothers varies according to their place of residence: by taking the example of women living with a man « professional » or « blue-collar worker », one can observe that this rate is always higher in the centre than in the peripheral areas, however great the number of children may be. The decline is especially strong for mothers with three children or more. The number of children is a less discriminating variable of labour force participation of women living in Paris than of that of those living in peripheral areas. In fact, due to their spatial structure, the centre and the near suburbs are more adapted to the needs of working mothers than the outlying suburbs. Restricted residential and housing choices, combined with time and space constraints, have probably reinforced the determination of women not to have a third child.