Who are the late mothers?

BACKGROUND: The frequency of late births (to mothers aged 35 or above) has increased since the 1980s, because the number of women over this age has increased (baby-boomer generation) and above all because their fertility has increased. The characteristics of late mothers have changed in the last 20 years: more primiparous women, more women in second unions, more women with a high educational level etc. Some of these trends are related to a general shift in the characteristics of the population, whereas others are the consequence of a change in women's fertility after 35 for some specific categories of women.
METHODS: We compared the characteristics of "late births" with those of births to mothers aged below 35 and with those of all women aged over 35. Fertility among several groups of women over 35 and the proportion of "late births" among different groups of births offer different insights into trends according to birth order, mother's marital history, level of education and occupation.
RESULTS: Late births are more often of order 1 because the fertility of childless women over 35 has increased substantially. Conversely, more births are to women living in a second union, mostly because second unions are becoming more common. Late mothers are more educated than before. On the one hand, the overall level of education has increased. On the other hand, highly educated women are more likely to be childless and without a partner at age 35, and fertility after 35 is now highest for childless women living in a couple. Late mothers are increasingly likely to have middle-level or higher-level occupations, because they rarely have children before reaching such positions.
CONCLUSION: Late mothers are now more numerous than 40 years ago and their mean social status has improved. This may change the way in which age is considered to be a risk factor for pregnancies: late mothers are more often primiparous, but their pregnancies are now more planned than before.