Many young parents, of course, complain of smothering attention from grandparents who won’t leave them or their children alone. Lorraine R., 49, a lawyer in Teaneck, N.J., does not place herself in this category.

“My mother-in-law seemed supportive when we were going through in vitro,” she said. But after her twins were born four years ago, grandma “didn’t offer to help,” she said. “She didn’t clean or cook a meal or change diapers.” (Like some others interviewed for this article, Lorraine R. requested that her full name not be used for fear of making a difficult family situation worse.)

When Lorraine R. and her children visited her mother-in-law’s swimming club, “she wanted to show everyone she had grandchildren, but then she sat as far away from the kiddie pool as she could,” Lorraine R. said. “She has no idea what our kids are like or what they’re interested in.”

In these parlous economic times, attitudes like that can have far greater consequences than hurt feelings. If a grandparent cannot or will not baby-sit for a working parent, day care or a nanny may be the only option, and may also be a financial hardship.

“It’s very expensive here, but we stayed on Long Island to be near my parents,” said a 43-year-old public relations consultant who lives in Syosset, N.Y., with her husband and three children, 7, 9 and 11. “My expectation was that my parents would be very hands-on.”

That has not happened, she said. Her parents, who are healthy and retired, live a mile away but keep their distance. “I’ll see three generations of families on vacation or at Splish Splash,” the Long Island water park, “and I’m amazed,” this woman said. “I’m in awe that there are grandparents there with the grandchildren, because it hasn’t been my experience.”