We were all dressed up for a party on a Saturday night, my husband and I, waiting for our son’s longtime babysitter to arrive, when the phone rang. The woman on the line announced that our sitter was in the hospital, told us where and the barest bones of why, then hung up. Geoff and I looked at each other, suddenly sick with worry. First, of course, for our sitter, who has cared for our seven-year-old son since he was born—would she be OK? And next, for the fragile scaffolding of our lives. What about Monday and Tuesday, when we both had packed schedules, and Wednesday, when I was due to leave for a five-day business trip? Would she be better? And if not, what on earth were we going to do?

Back up 44 years. In 1969, the year before I was born, my parents moved from New York to Los Angeles. After struggling to find a job, despite two master’s degrees, my mother started as a Christmas clerk at Bullock’s before getting hired in her field, as a librarian at the University of Southern California. I was looked after by babysitters until I was nine, when I became a latchkey kid, like many of my fellow Gen Xers. As I was growing up, my mother would tell me, “Jennifer, when you were born, I couldn’t wait to get back to work!”

She was proud of her career and her financial independence, and because of her, working has never felt like a choice to me. It’s a given. Automatic, like paying taxes. I’ve had one job or another since I was 14, and I’ve supported myself since I graduated from college at 22. I love being a magazine editor. But when I got pregnant at 34, people in my office kept asking if I would return after maternity leave. They seemed to think I was being coy when I said “Of course!” and they looked surprised when I walked in 12 weeks after my son was born and powered up my computer, as if I’d ever been anything but clear about my intentions. Except why wouldn’t they wonder? Two other women were pregnant the same year I was, and neither came back to her job.

At the time, I didn’t think about it much. I was too busy trying to figure out how to breast-feed and get my work done and manage it all on five hours of sleep. I never questioned my decision to work, and I also didn’t question theirs not to. One woman returns to the office after maternity leave; another doesn’t. Why does it matter? Isn’t one path as valuable as another? I was naive to think it was so simple. For women, the decision whether to work outside the home or raise kids full time is the ultimate manifestation of assumptions about femininity, motherhood, marriage and finance. And like it or not, it’s our first salvo in the mommy wars.

Let’s be clear: It is a privileged group of women and men who ever confront this decision. Many don’t have anything approaching a financial choice when it comes to working. Others have children whose health problems dictate that someone be there to manage their care. The issue is further distorted by socioeconomic class: One mother stays home because child care for her kids would cost more than she could possibly earn or because she can’t find appropriate employment; another stays home but has full-time help and plenty of money left over. There is a danger in lumping people together too categorically.

Except that schools do tend to lump people together. And so when my son toddled off to a nursery program at the age of three, I began to experience the gulf between working mothers and stay-at-home mothers (though we know that all these women work), between the ones who treated maternity leave as temporary and those who caromed off it into a new life. My son’s school is lovely and sweet, and I feel grateful to have him there. Still, these days schools require a lot of volunteering and chaperoning and class-mommying. There are presentations on bullying to attend and potlucks to host and end-of-the-year gifts to arrange. For any parent, it’s a never-ending expression of personal values. In which of your commitments will you invest the most time?