"You don't want children? Really? Why?"

"Of course not. Why would I?"

Though it may sound glib, an increasing number of millennial women may be offering up this answer to friends and family who don't understand why they choose to go childless. And judging by recent data from National Center for Health Statistics, this choice is becoming less of an anomaly.

"I've never liked children," Rashmi Chugani, a 24-year-old graduate journalism student at Columbia University, told Mic. "I've never had a maternal instinct. It's a selfless act and if I have kids I want to be as good of a parent as [my parents] were to me, but right now I'm not in a position to take care of someone else."

Chugani is hardly alone. The number of women in the U.S. who opt out of motherhood has doubled since 1970, according to the Pew Research Center, and the trend shows no sign of slowing. This is arguably both reflective of women being valued for more than motherhood and a question of practicalities: Given an economy of low-wage, high-demand jobs, the high cost of rent, the lack of affordable or subsidized child care and crushing student loan debt at the beginning of adulthood, it's understandable more women would delay childrearing or forego parenthood altogether. What's more, the burdens of child care still fall largely on women's shoulders.

Kathy Willens/AP

Mothers still have it the worst in the workplace: In recent decades, the wage gap between mothers and non-mothers has grown wider than the gap between women and men; motherhood now indicates a lower wage more often than gender alone. Women who have children are also more likely to be unemployed or work part-time. Add that to the fact that the cost of child care has almost doubled since 1985; that "the cost of putting two children in child care exceeded median annual rent payments in every state" in 2010, according to CNN Money; and that even taking one single year of parental leave chews off 20% of a woman's salary over the course of her career, as the Economist reported, and the financial and professional impact of having kids becomes particularly daunting.

In fact, women, especially those with higher education, can largely avoid the gender wage gap by not having children, and avoiding what researchers Paula England and Michelle Budig have dubbed "the motherhood penalty."

Millennial women don't want it all. The Sheryl Sandberg model of balancing career and family has made a lot of sense for some mothers but may resonate less for younger women who simply don't want to juggle ballet recitals with boardroom meetings. For most young women, working is not an option — it's a necessity. Some data even shows that young women today focus on their career more than their male counterparts. That shift has had a significant impact on women's family decisions; because young women today rank their career as more important than it has ever been for their demographic, having children has become an option instead of a prerequisite for a fulfilling adulthood.

Yet, socially, women can't win: Despite the fact that having children remains a substantial burden in today's society, women — working or not — are treated as selfish or strange for choosing not to raise a family. Alex Kane Rudansky, a 23-year-old assistant account executive at a marketing agency in Chicago, says she prefers to focus on her career, but feels judged by coworkers for admitting to not wanting children. "It's acceptable to have a kid and a career, but we're not at the point where it's acceptable for women to have a career and no child," she told Mic.

The work-life balance model suggested by older women like Sandberg may be achievable for some, but for those of us who can't afford au pairs, nannies or straight-up day care, such a financial hit isn't necessarily appealing. Indeed, the 2013 viral image of supermodel Gisele Bundchen breastfeeding at work is almost a parody of what being a working mother actually looks like. Many workplaces still don't have the appropriate space and facilities for breastfeeding, lactation discrimination lawsuits persist.

Most offices also don't include three people dedicated to ensuring that you look fabulous. Bundchen might be also technically be a millennial, but for the rest of us, motherhood will not be this glamourous.

Running out of time: Breastfeeding blowouts and photo shoots aside, there has been a profound disconnect between the speed at which women have been asked to take full-time roles in the workplace and the rate at which we've adapted laws and social programs to support this drastic change in the lives of women. The reality is that if you're both a mother and an employee, every day is a double-shift (or even a triple-shift, if you include caring for sick relatives the way many female workers are expected to do).

Women are spending more hours at work, but research finds they are spending just as much time with their kids as they did in the 1970s. Time is a scarce resource, and mothers have less and less of it — so much so that the term "leisure gap" was coined to highlight this gendered discrepancy. On average, men get five additional hours per week compared to women. What gives? What's the point of leaning in if you never have any time to lean back?

Sheryl Sandberg Bloomberg/Getty Images

Young men don't face the same kind of pressure. Men who don't want children are not necessarily shamed for that choice. "Single men who are of childbearing age who put their careers first, they are not questioned," Rudansky said. "They are lauded by their peers as eligible bachelors. When I say it's not for me, I'm questioned and put into categories."

Kim*, a 31-year-old interior design and architecture student, said neither she nor her fiance want children, but to avoid conflict, they told her in-laws that it was his decision. Both Kim and her fiance are considering sterilization, but she is the only one whose decision is consistently questioned by friends and acquaintances. "My fiance doesn't get these questions, but I do. It's patronizing," she said.

For young men, having children is a rational choice. There is no workplace penalty for men who decide to become fathers. As a matter of fact, male workers get rewarded when they choose to do so: The so-called "daddy bonus" is based on data showing that men actually earn more respect, promotions and salary when they become fathers. One study showed that including "PTA" on a resume made women twice as likely not to get a call back for a job, but increased the likelihood of getting a callback for men — even if the resumes were otherwise identical.

Leveling the playing field. Based on this evidence, why are we shocked that young women are opting out of motherhood? The benefits of parenthood — like the feelings of love from family — are immeasurable, and shaping and molding children is an important part of life for many people. But until federally mandated leave policies and support systems like affordable day care are mandated, it's not unreasonable for some to question taking the risk of parenthood.

Despite it being better for employee productivity and good for the economy, the U.S. is the only industrialized nation without federally mandated paid parental leave. Unfortunately, the same politicians who seem obsessed with the American family and its preservation seem to have little motivation to institute laws to thwart millennials' growing disinterest with parenthood. President Barack Obama demanded Congress send him a paid leave bill at his State of the Union address in January, but Republicans have instead used every excuse to ignore Obama's mandate.

Young women may be the ones delaying having children, but politicians are the ones who need to get their act together. While they delay taking an initiative to change our flawed family leave policies, millennials' aversion to children will likely continue to grow. Rather than shun women who make an arguably logical decision not to have kids, we should reserve our judgement for policymakers who fail to bring us into the 21st century when it comes to family planning.

Don't blame the woman; blame the system.

Some names have been changed to allow subjects to speak freely on private matters.