Traditional day care works fine, unless you're a single mom about to take a business trip.

Or your home day care provider catches the flu.

Or you have a last-minute dinner meeting on a Thursday evening and the neighborhood baby sitter is busy with track practice.

Parents who have these problems - or who just like the idea of custom, in-home service - are turning more and more to nannies. The demand is so great that local nanny placement agencies can't keep up.

Balancing two children and two careers in upper management, Mary and Don Coffin of Des Moines, Iowa, began using a local nanny agency in 1995. They've had four longer-term nannies - and another child - since then, and recently switched to a part-time arrangement.

Mary turned to the agency after the arrival of their second child, whom the couple adopted, left them little time to plan.

"At that point, one of the decisions I made was, if I'm going to do this - work and have children - I'm going to provide the least stress to them," Mary says.

"Getting them up in the morning and driving them to day care, I didn't want to do that. It was something we had the ability to afford and I wanted that luxury for my children."

For the Coffins, a nanny provided needed flexibility in their schedules. Their children seemed to have fewer illnesses than friends' children who attended day care. Plus, nannies helped with laundry, grocery shopping and errands.

"When you come home, you can be fully dedicated to being with your child," Mary says.

Most importantly, the Coffins have maintained the relationships they began with their nannies. Mary considers the women who have watched her children an extension of the family.

Nannies typically stay with families one to three years, says Angela Wilson, co-owner of American Professional Nannies in Des Moines. Some stay longer.

"Every nanny we have had over the 11 years has continued to come back, go to dinner with us," Mary says. "They loved my children, cared for them deeply and haven't wanted to lose that connection and that's a great thing for them and our family. No one hurts from having others love them, too."

Using a nanny isn't just for executives.

Wealthy parents, single moms who travel and middle-class, two-parent, working families are all seeking nannies, according to nanny services.

"A nanny is affordable," says Cherish Anderson, who started her own nanny service in 2003. "If you have two children, it's equal to the cost of a day care center, and it's more effective if you have three children."

Nannies cost about $400 to $450 a week. Live-in nannies may charge about $50 less per week. In addition, services charge application fees to families (typically $100 to $125) and placement fees, which differ depending on whether the placement is temporary or permanent.

While some may opt to do their own nanny search, nannies contracted through services come with background and reference checks, and many nanny candidates prefer having a third-party involved.

"A lot of times, nannies feel more comfortable going through an agency," Wilson says. "It's pretty scary answering a blank ad and going to someone's home."

In addition to child care, many nannies perform some light housekeeping.

Nanny Brady Weible first worked at a day care center, but has now nannied for eight years and praises the arrangement for its freedom and the close relationships formed caring for a smaller number of children. She typically spends several years working for a single family.

"On gorgeous days, we can spend the entire afternoon at the park, rather than the allotted 10 minutes at the day care," she says.

She advises parents to interview as many people as possible and trust their instincts about who will work well with their family.

Agencies can ease the process.

"I send two people to interviews and most likely, it's the first person who gets there that they hire," Anderson says.