It doesn't take a college degree to figure out that higher pay puts families in better positions to provide for kids, when they do arrive. A woman is also much more likely to be married or partnered for the long term at 30 or higher than at 22, which means shared caregiving and a second income, all of which also make childrearing easier. Everybody loses when the women in their families earn less. It's not just a women's issue.
Family isn't all about money, but it's always had an economic underpinning since at its base reproduction is about workforce. Families enjoy one another's company generally (okay, family has historically comprised a huge part of what people do), but employers and society have a major stake, too, in the work the family does to produce and feed young bodies and educate and civilize young minds, so that a steady stream of able and cooperative workers flows to the job site, wherever it may be.
Back in the pre-contraceptive day, women could be counted on to have and rear kids without compensation or support because they had few other options, if they had sex.
But since the arrival of hormonal birth control, women have the option not only to have fewer children (the birthrate fell 44 percent in the fifteen years after the Pill arrived in 1960 and has stayed in the same ballpark since), but to have them either much later in life (after they've completed their educations and established at work) or not at all. Though most people still indicate a desire for kids, others have no interest. ("They're messy," notes one happily childless married woman in her 50s who spent a lot of time babysitting as a teenager.)
With all the time freed up from child-bearing and child-rearing, women have been able to fill in for the "man-hours" lost to the workforce by the birthrate fall. When women can work in the same jobs as men, only half the number of babies is needed, a more efficient system. Also a fairer system, as it works out, since only when they're educated and able to earn their own money can women move into policy-making roles in business and society and get their voices and concerns heard.
Only limited adjustments have been made to the family support infrastructure to offset the shift of working women's time into the workplace. Where other nations supply childcare at public expense, on the principle that a well-educated workforce benefits everyone, the United States provides only limited services, to a limited set of the poor, through Headstart. Everyone else is on their own, and good care is too pricey for most, which affects both the education of children in bad care and the workforce participation of mothers who stay home or work part time in low-wage jobs to accommodate kids.
Birth control allows women to begin to change the terms of the reproductive deal so that society gets to cover some of the costs of childrearing, from which we all benefit, and women forego less in the way of compensation. Pay equity guarantees and a good, affordable publicly funded childcare system for all families would be a good start.