If you have to bring your kids along on business trips, it helps to bring their grandma, too.

When you’re a young scientist shooting for tenure, you have to jet around the country talking up your research at academic conferences.

When you’re a young mother nursing a newborn, you have to take your baby everywhere you go.

In 2007, shortly after Stephanie Cosentino, then 31, gave birth to her first child, Luke, she was hired as an assistant professor of neuropsychology at Columbia University.

She couldn’t sit out a year’s worth of conferences while she was breastfeeding Luke, but she couldn’t bring him along without some help.

Her husband, a standup comedian, would have joined them, but that would have meant passing up gigs. Her mother, on the other hand, was a legal secretary, and she could take paid time off.

So again and again, Ann Cosentino, who lives near Stephanie and her family in New Rochelle, New York, stepped up as a traveling babysitter for her grandson. In 2012, Stephanie gave birth to a daughter, Willa, and Ann was her traveling sitter, too.

With Stephanie and either Luke or Willa, Ann went to North Carolina, New Mexico, Virginia, and Hawaii, among other places. But the trips were “in no way a vacation” for her, Stephanie says.

Stephanie paid for her mom’s plane tickets, but funding an extra hotel room for her would have been tough, so the three generations always squeezed in together.

And since Stephanie was putting in long days, so was Ann.

At a Hilton in Alexandria, Virginia, Willa suddenly stopped taking bottles. Every time she got hungry and her mom wasn’t around, she just howled.

Ann wanted to soothe her with some nice long walks, but it turned out there was nowhere to go.

“There was no sign of civilization anywhere,” says Ann. “It was just corporate park after corporate park after corporate park.”

Stephanie recalls, “And I would get these text messages in each of my different sessions: ‘Must come now.’ ‘Crying.’”

“My mom is such a good sport … she is the most low-maintenance person you’ll ever meet. So nothing bothers her,” says Stephanie, now 38 and still a tenure-track professor at Columbia. Through her research, she’s developing new tests to diagnose Alzheimer’s disease.

Ann, now 66, says she had fun on the trips, and that using her paid leave for them was no big deal.

Being a grandmother, she says, is “heaven on earth.”

“It’s my life.”