By Steven Reinberg
Researchers looked at information on more than 1 million children born to Swedish women who were followed for nearly eight years.
"The overall risk of cerebral palsy was about 2 cases per 1,000 babies born," said lead researcher Dr. Eduardo Villamor, a professor of epidemiology at the University of Michigan in Ann Arbor. "Women with the most severe forms of obesity who have babies born at full term may have about twice that risk."
Moreover, the prevalence of cerebral palsy has increased in children born at full term, he noted.
However, Villamor stressed that the study findings only show an association between a woman's weight during pregnancy and the risk of cerebral palsy, not that maternal obesity causes the condition.
"Although the effect of maternal obesity on cerebral palsy may seem small compared with other risk factors, the association is of public health relevance due to the large proportion of women who are overweight or obese worldwide," Villamor said.
Cerebral palsy is a group of disorders that affect the ability to move and maintain balance and posture. It's the most common motor disability in childhood. The condition is caused by abnormal brain development or damage to the developing brain that affects the ability to control muscles, according to the U.S. Centers for Disease Control and Prevention.
Overweight and obesity in early pregnancy may increase the risk for a number of complications and can adversely affect the health of mothers and children, Villamor said.
Some studies suggest that weight loss before pregnancy may decrease some of these risks, he said.
"Although we don't know yet if this also applies to cerebral palsy, weight loss before pregnancy among overweight and obese women may offer some health benefits during and after pregnancy," Villamor said.
One obstetrician concurred.
"There continues to be evidence of many different repercussions and outcomes associated with being overweight or obese," said Dr. Siobhan Dolan, a medical advisor at the March of Dimes.
"All the data is pointing to the same issue -- that it's good to get to a healthy weight before pregnancy and to gain the right amount of weight during pregnancy," she said.
For the study, Villamor and colleagues collected data on more than 1.4 million children born in Sweden from 1997 through 2011. More than 3,000 children were eventually diagnosed with cerebral palsy.
For infants born at full term, who accounted for 71 percent of all cerebral palsy cases, the association between maternal obesity and cerebral palsy was statistically significant. But it was not statistically significant for preterm babies, the researchers noted.
About 45 percent of the association between maternal weight and cerebral palsy in full-term children was seen in infants who had breathing complications, they added.
The report was published March 7 in the Journal of the American Medical Association.
A cerebral palsy expert said maternal obesity isn't the only risk factor for the condition.
"About 30 to 40 percent of cerebral palsy is genetic," said Dr. David Roye, executive director of the Weinberg Family Cerebral Palsy Center at Columbia University in New York City. He is also the medical director of the Cerebral Palsy Foundation.
"As you are planning a pregnancy and entering pregnancy you want to be healthy," Roye said. Being at your best includes maintaining a healthy weight, avoiding smoking and alcohol and continuing to exercise, he said.
The time to lose weight is before you become pregnant, Roye stressed.
"It would be wrongheaded for someone, particularly after they became pregnant, to decide they are going to lose weight -- that's not a good plan," he said. "You should be at your best and fittest before you go into the pregnancy."