Professor Richard Fleming, director of the Glasgow Centre for Reproductive Medicine, said that the root cause was because women were starting their families later in life.

BBC: The cost of fertility treatment 'tourism'

Women in the Northeast who married and started families later in life tended to vote Democrat while their Midwestern peers who got a head start on marriage and family building often voted Republican, Belgian demographer Ron Lesthaeghe found.

CNN: STORY HIGHLIGHTS

Life is slowing down and speeding up at the same time: families arrive later, even as careers are accelerating.

ECONOMIST: Bagehot: Generation Xhausted | The

Older women may have entered the workforce later in life than their male counterparts so they have fewer years of work experience, due to marriage and raising families, than their male colleagues and thus earn less.

FORBES: Good News for Younger Women: There's a Smaller Wage Gap