“People expect mothers to be less committed and therefore give them less responsibility and pay them less from the start.”

By Joan C. Williams & Rachel Dempsey (Authors, The New Girls’ Network)

An article in this weekend’s New York Times shed some more light on Silicon Valley’s worst-kept secret: it has a woman problem. Its look at female founders of tech start-ups who also have children shows a remarkable lack of self-consciousness about Maternal Wall bias, the strongest and most open form of gender bias today.

According to the article, women make up 10% of founders at high-growth tech companies, and raise 70% less capital than men do. There are a lot of reasons for this; we discussed sexual harassment in our last post, and we’ll take on the meritocracy myth in our next. But bias against mothers and pregnant women may be Silicon Valley’s loudest unspoken bias – so deeply entrenched that it’s taken for granted that mothers can’t run a business.

In a refreshing piece referenced in the Times story, angel investor Paige Craig actually states the bias out loud: “A pregnant founder/CEO is going to fail her company.”

“I’m thinking how in the hell is this founder going to lead a team, build a company and change the world for these businesses carrying a kid around for the next few months and then caring for the kids after?” he asks – looking for an answer. Here’s ours.

There are several strands to pick apart here. One is that no one seems to be making an important distinction: there’s a difference between a woman who has kids, a woman who’s pregnant, and a woman who might get pregnant. Only one of those three may take time off for maternity leave. That doesn’t even come close to explaining the gender gap between men and women entrepreneurs.

Aileen Lee, a partner at Silicon Valley venture capital firm Kleiner Perkins Caulfield and Byers, tries in the New York Times article to make the fear of investing in women gender-neutral: “If someone was having some surgery that was going to put them out for three months, it’s something you should consider, with a man or a woman. What is the impact of having the C.E.O. or visionary out for three months?”

Except men don’t have trouble getting funding because they might get sick and need surgery.

Even before women have kids or even plans to have kids, they may face doubts about how committed they will be as mothers. “I think there are a lot of challenges for women because VC’s are thinking: ‘Uh-oh. When are those women going to get pregnant? When are they going to get distracted?’ I think that kind of stuff is pervasive, and it’s unfortunate,” one entrepreneur quoted in the Times article observed.

And once women have children, they’re subject to Maternal Wall bias, which is an order of magnitude larger than bias against women in general. The best-known study on this bias gave people resumes that were identical except that one, but not the other, mentioned membership in the PTA. Mothers were 79% less likely to be hired and offered an average of $11,000 less in salary. Note that this gap has nothing to do with performance – the two subjects’ resumes were exactly the same. People expect mothers to be less committed, and therefore give them less responsibility and pay them less from the start.

This leads to another key point. Mothers who drop out to spend time with children are often depicted as being pulled by a biological impulse. But there are significant pushes as well – particularly in Silicon Valley. Sometimes women leave because they are weary, worn down by dealing with year after year of glass ceiling discrimination. Based on interviews we’ve conducted for an upcoming book, women in tech often have to prove themselves over and over again, and are expected to be contented with doing the work without the title, in good feminine fashion.

One woman who works in Silicon Valley told us she sees this pattern again and again: “Women would hit 30 years old, and they were hitting the same glass ceiling that I’ve been hitting for a long time. And if they could, if money has good, they would just start having babies and drop out because they want to have kids anyway, and it’s hard to show up every day and fight and fight and fight.”

The result is a self-fulfilling prophecy. Women give up on their startups, or just don’t start them in the first place, because the system is set up in a way that’s unfriendly to women and downright hostile to mothers. The people responsible for the system, in turn, point to the low numbers of women as a sign that they aren’t interested or qualified, and therefore refuse to make the changes that would open the industry to the other half of the population.

This post was originally posted at Huffington Post.

About the guest blogger: Joan C. Williams is Founding Director of the Center for WorkLife Law and a central role in documenting workplace discrimination against adults with family responsibilities. The culmination of this work is Reshaping the Work-Family Debate: Why Men and Class Matter. Joan has played a central role in documenting workplace discrimination against adults with family responsibilities and works with employers, employees, employment lawyers. Follow her on Twitter at @JoanCWilliams.

About the guest blogger: Rachel Dempsey is co-writing a book with Joan C. Williams titled The New Girls’ Network about common biases women face at work and how to overcome them. She has blogged for Amnesty International, and her posts with Joan have been published on the Huffington Post, Psychology Today, New Deal 2.0, and MomsRising and excerpted in Time magazine. An employee at a national class-action law firm, she worked for plaintiffs on gender discrimination cases.