Gum disease, caused by a bacterial infection that breaks down gum tissue and can cause tooth loss and serious health problems, is a particular problem during pregnancy. Hormonal changes appear to make a pregnant woman more susceptible to developing gum disease, yet the standard antibiotic-based therapy is not recommended because it stains the baby's teeth.

Dentist have also been concerned that by aggressively treating gum disease patients with teeth cleaning, bacteria could get into the pregnant woman’s bloodstream causing harm to the baby.

But those fears are baseless, the new study shows.

"Women can be confident that it's not going to have clinically meaningful effects on their child's development," said Dr. Bryan Michalowicz, whose findings are published in the journal Pediatrics.

Michalowicz, a dentist at the University of Minnesota School of Dentistry in Minneapolis, and his colleagues tested more than 400 two-year-olds, who'd been born to mothers with gum disease.

Half the mothers had been treated with aggressive teeth cleaning, called scaling and planning, during pregnancy, while the rest had not.

The researchers found the kids did just as well on language, motor and mental tests regardless of whether their mothers had been treated.

On the other hand, treatment didn't seem to benefit the kids either. That was the researchers' original hypothesis, because earlier studies have linked gum disease to developmental delays.

"We asked the question, does treatment of periodontal disease in pregnant women improve child development?" said Michalowicz. "We found it doesn't."

The researchers did find a slight increase in toddlers' test scores when the mothers' gum disease improved. But the effect was so small it doesn't have any practical consequences, they say.

Nonetheless, he said, "As a dentist I think that improving oral health is a goal in its own right."

Bad oral health in pregnant women has long been suspected as a link to miscarriages.

A 2010 study published by the British journal Obstetrics and Gynecology, reveals the case of a 35 year-old woman who had the common gum disease gingivitis.

She delivered a stillborn baby at 39 weeks and doctors were able to trace the oral bacteria in the mother’s mouth to bacteria found in the baby’s bloodstream, lungs and stomach. Scientists believe that any disruption to the amniotic fluid, the liquid that surrounds an unborn baby, could pose a risk to both mother and baby making the infection from gum disease a real risk.

Dr. Marjorie Jeffcoat, a dentist at the University of Pennsylvania in Philadelphia who wasn't involved in the Minnesota School of Dentistry study, said it couldn't rule out that treatment might benefit the baby in some cases.

"You need to have a higher risk population in order to draw a conclusion," she told Reuters Health. "I wouldn't jump to the conclusion that we should let periodontal disease run rampant in pregnant women."

But, she added, women should try to maintain good oral health in the first place.

"They need to use a soft toothbrush and floss the right way," wrapping the floss around the tooth, she said. "The first goal with almost all dental disease is prevention, prevention, prevention.”

The following guidelines were developed by the American Academy of Pediatric Dentistry, in response to the growing concern surrounding oral health during pregnancy:

- Oral Health Education - Counseling and early intervention by healthcare providers such as physicians, nurses, and dentists to provide expectant mothers with the tools and resources necessary to understand the importance of oral health care during pregnancy.

- Oral Hygiene - Removing the bacterial plaque, which researchers have connected to preterm birth and low birth-weight babies, is essential. Using the correct brushing and flossing methods greatly increase the amount of plaque that is removed from the teeth and gums.

- Fluoride - The American Dental Association recommends the use of toothpaste with fluoride by persons over the age of six. Echoing their sentiment, the AAP oral health guidelines advise the continued use of fluoridated toothpaste during pregnancy, and recommends the use of an over-the-counter alcohol-free fluoride rinse to help reduce the amount of plaque in the mouth.

- Nutrition - Educating expectant mothers about proper diet and nutrition during pregnancy will limit unnecessary sugar intake and in turn, prevent plaque build up. Talk with your dentist or pediatrician.

- Treating Existing Tooth Decay - Expectant mothers are encouraged to have existing tooth decay treated during their pregnancy, which experts believe is a completely safe practice during pregnancy. Restoring decayed teeth will help achieve oral health by removing the bacteria associated with tooth decay.

- Transmission of Bacteria - Expectant mothers are discouraged from sharing food and utensils in order to prevent the transmission of the bacteria known to cause tooth decay.

- Use of Xylitol Gum - Expectant mothers are encouraged to chew Xylitol gum (four times a day) as research suggests that chewing this gum may decrease the rate of tooth decay in children.