Women in their early 40s are getting pregnant more often.

A government report released on Wednesday shows pregnancy rates among women in their early 20s falling nearly 18 percent from 1990 to 2008. But pregnancies among older women rose far more dramatically: rates for women ages 40 to 44 went up nearly 65 percent. There were just 11.4 pregnancies per 1,000 women in that age group in 1990, compared with 18.8 in 2008.

Women in their 20s may be delaying pregnancy, but older women seem to be picking up the slack. Rates for women ages 35 to 39 rose, too, to 78.5 births per 1,000 women in 2008 from 67.5 in 2000, and a similar increase (from 2000 to 2008) can be seen among women 30 to 34.

These numbers come as little surprise to anyone following the question of when (and if) women have children. Young women in career mode are putting off marriage and children to the point where some are having conversations with their parents about freezing their eggs. More educated women are looking for options to protect their fertility as they invest in their professional futures.

But alongside that tale of delayed pregnancy and an attempt to fit parenthood into a life that includes marriage and career is another story: that of women under 30 who aren’t delaying having children, but are delaying marriage, and for whom career is uncertain at best. Pregnancy rates may be lower among women in their 20s, but among those same women, more than half of births occur outside marriage.

The more educated a woman is, the more likely she is to have children later in life, and the more likely she is to be married before she has a child. This small set of demographics doesn’t just reflect changes in the age at which women become pregnant. It’s a tiny snapshot of a growing socioeconomic divide among parents: one that has an impact on our priorities and our politics as well as our culture as a whole. What changes in a country where a growing number of women are becoming mothers as others in their cohort become grandmothers? We’re going to find out.