Chick lit is growing up. Rather than looking for Mr. Right, today’s crop of Bridget Joneses is dealing with diaper changes. A recent entrant into this field of “Mommy Lit” is Katherine Stewart’s “The Yoga Mamas” (Berkley Trade Paperback, 340 pages, $14), a fun and funny novel about a group of women who meet and become friends in a SoHo prenatal yoga class. Ms. Stewart, herself a downtown resident and the mother of a 3-year-old girl, recently discussed the novel and its New York themes.

Q: What inspired you to write “The Yoga Mamas”?

A: The short answer is that I went to my own prenatal yoga class, and thought it would be a great setup for a novel. But the truth is that when I was pregnant I found there was a big space missing on the bookshelf, a whole part of this extraordinary experience of life that hadn’t made it into any of the books that I’d read. … I never had a “sorority-type” group of women friends before, but after getting pregnant, I suddenly understood what it was all about.

These days, it seems like prenatal yoga classes are a New York pregnancy rite of passage. As with the characters in your book, it seems strong friendships are formed between the women in these classes. Is there something about yoga and pregnancy that bonds people?

Yoga teaches strength and flexibility, and I think motherhood does as well. I also think yoga works because pregnancy is all about the body. You suddenly look at your body in these new ways. It’s beautiful but also scary, and when you can share that experience with other people, you don’t feel like such a freak.

Some of the characters give birth at the same time, but they have very different birth experiences. Why did you decide to handle the labor and delivery scenes the way you did?

When you are about to have a child, you enter a whole world of ideologies about how you should do it. Some people say you should be as natural as a cow in a meadow. Others feel you are a fool if you don’t make use of every tool available to modern science. Frankly, I had trouble making up my mind. … What I saw in real life is that many of the plans went out the window the moment labor kicked in. Whatever happened, happened. That’s what I tried to represent in my book: Susan, the earth mother, ended up with a heavily technologically assisted birth, whereas Margaret, the technophile, ended up delivering her baby without the help of anesthesia or other medications.

The topic of money – namely, the narrator, Laura’s, lack of it compared to her Yoga Mama friends – runs throughout the book. … But even though she is an outsider, Laura buys into some of the trappings of that world. She makes self-deprecating comments about her Old Navy clothes, but she scrimps to get the Bugaboo Frog.

Yeah, Laura gets caught up in the competition. We all do. That’s just part of life – none of us wants to be a nun dressed in a hairshirt. But I think the book brings out the humor of her predicament. And in the end, to some extent, Laura learns a lesson that it’s not all about the stroller.

The Yoga Mamas meet up at a restaurant called Healthy Harvest. While they are pregnant, they are greeted with welcoming smiles. But when they return some months later with their babies, they get dirty looks and, in a gesture of solidarity, end up nursing their babies in unison. Laura goes on to bemoan the difference between how a pregnant woman is treated in New York versus the way a woman with an actual infant is treated here. Is that true to your experience?

When I was heavily pregnant, I felt like a rock star. Strangers smiled at me, offered words of encouragement, gave me first-class treatment. All that ended as soon as I delivered my baby!

Stroller pressure aside, one nice thing about the book is the generally supportive, noncompetitive nature of these friendships. Have you found that to be the case in your own mothers’ groups?

“The Yoga Mamas” is a book that celebrates female friendships, and in my own yoga class I found a lot of that. On the other hand, I know from personal experience that few people are harsher judges of mothers than fellow mothers. Just a glance at a child’s mismatching socks or a casual, “Oh that school” is usually enough to convey immense cattiness. That, however, will be the subject of my next book: I’m currently at work on a novel about the Manhattan preschool race.

That makes sense, as some of the women in this book – while still only pregnant or the mothers of infants – are already trying to get their children into the “right” preschool.

I still know people like that. Some of them are my friends. One friend signed up for a certain local church which has a prestigious preschool attached … and she isn’t even pregnant yet. And she’s a pantheist!

Well, I guess it’s all material.

Exactly!