Come 4 o’clock on most Fridays, a group of eight mothers in Chestnut Hill, an affluent neighborhood in Philadelphia, gathers for drinks.

They have been following the rules all week, dutifully potty-training, wiping noses and transporting their progeny to schools, classes and doctors. As their young children play nearby, the women said, they sit around in one of their yards or living rooms, drink glasses of Cavit pinot grigio or cups of Yuengling lager, and unload. They talk of problems at the pediatrician’s or at school. They dole out pizza or cook hot dogs. Sometimes, they dance with the children.

“You just automatically relax,” said Kelley Ann Mansfield, a mother of two who founded the Friday group five years ago. “It’s before you take the first sip, as soon as your hand touches the bottle. It’s like, ‘Man, I’ve gone through the day, I need to treat myself.’ ”

Happy-hour play dates are here. Between runs to soccer and ballet classes, fund-raisers and homework projects, some stay-at-home mothers are sipping cocktails at afternoon spa parties, drinking bloody marys at play groups and toting wine and wine coolers to parks and friends’ decks while their children frolic nearby.

These women are not out to get drunk, they say. And they insist they are not drinking out of need. Rather, they are looking for a small break from the conventions of mommy-hood — a way to hold on to a part of their lives that existed before they had children and to bond over a shared disdain for the almost sadistically stressful world of modern parenting.

They know they will be criticized. They live, after all, in an age when many parents are so protective, they hire consultants to childproof their homes. Most acknowledge there can be a fine line between social and problem drinking and that the mix of children and alcohol is a dangerous one. And women who are pregnant keep away from the bar.

But some women are almost defiant in their defense of the afternoon group “momtini,” as one blogger calls it, and they speak out on the Web, in books and in interviews. The mothers do not know how many like-minded women are out there — there is no real way to quantify it — but they sense a change.

Some say the mother get-togethers are a throwback to the 1950s, when adults had more time to themselves and children were not always the center of attention. Martinis were in vogue; today’s obsessive, hard-driving, Harvard-or-bust parenting scene was not.

Teresa Klauber of Greenwood, S.C., wrote that she much prefers the cocktail play groups she has attended to other play groups, “where it seems like everyone is trying to compare their child to everyone else’s.”

“Too competitive,” she added, in an e-mail message. “This is much more social and well, friendly.”

Christie Mellor, in her book “The Three-Martini Playdate: A Practical Guide to Happy Parenting” — one of a spate of books over the last few years that urge parents to ease up — advised mothers to mix a few martinis during an afternoon play date. If the parents of your child’s new preschool friend are shocked, she says, they probably are no fun, anyway.