Conventional wisdom has for years been that women can do it all: work full time, hold the same jobs as men and still be loving, nurturing moms at home.

Many women have been able to successfully balance career and motherhood. But a new study suggests that when moms do that, the children suffer.

Researchers at Columbia University say when moms work full time during the first nine months of their child’s life, those children end up with weaker learning and verbal skills by the time they reach age 3. The problems last until the kids are 7 or 8 years old, according to the study.

The bad effects don’t turn up when moms work only part time, or don’t go back to work until their child turns 1.

Other factors also come into play. Among them are the quality of child care kids get when moms are at work, the home environment and the sensitivity level of these mothers when they’re actually at home with their children.

But in the study, even when all these needs were being met and the mom worked more than 30 hours a week, the kids’ development was still slower.

So what’s a mom to do?

Not panic, says one of the study’s authors.

"We are not saying women should be paranoid, we are not saying your kid’s life is going to be ruined if you go to work," said Wen-Jui Han. "We are saying there’s something we can do about it, let’s do something about it."

The researchers have some recommendations, all of which have companies and the federal government spending more money to make it easier on moms. One idea is to expand paid maternity leave to 10 months, or to allow moms to work part time at full pay until their kids reach the age of 1.

The federal family and medical leave act provides 12 weeks of unpaid leave. Another idea is for the federal government to make sure that moms on welfare are not required to go back to work while their children are less than a year old.

The study's bottom line is that women cannot have it all, at least not in the first year of their child’s life. Staying at home might not be the best thing for a mother's career, but it may be good for her child.

Some groups are backing the study.

"There's no question it's true," said Dr. Janice Crouse, a senior fellow at the Beverly LaHaye Institute at Concerned Women for America. "There’s no question that a mother’s care is the best care for a child, especially in the first year."

The institute reported similar findings a year ago and found that despite the quality of non-mom child care, there is a risk of kids turning out to be bullies or having other behavioral problems. Crouse's institute recommended that moms do not keep their kids in child care for more than 10 hours a week if they want their children to develop socially and in other ways.

"There is no substitute for a mother's care," Crouse said. "Often times, our children are the last thing on the priority list."

Lauren Noyes, director of U.S. House relations for the Heritage Foundation, a Washington-based conservative think tank, is six months pregnant. She fully agrees with the study and said she has already asked her employers for a part-time schedule after her baby is born, else she may not come back to work during that first year.

"Intuitively, I just knew it was not best for my baby for me to be away from it that much," Noyes said.

Fox News' Liza Porteus contributed to this report.