LONDON (Reuters) - Obese women are more likely to give birth to children with spina bifida, heart problems, cleft palate and a number of other defects, British researchers said on Tuesday.
The findings published in the Journal of the American Medical Association underscore obesity's role as a major health problem and add to evidence that being too heavy while pregnant carries risks for both mother and child.
Katherine Stothard and colleagues from Britain's Newcastle University combined data from 18 studies to look at the risk of abnormalities of babies whose mothers were obese or overweight.
Obese women were nearly twice as likely to have a baby with neural tube defects, which are caused by the incomplete development of the brain or spinal cord, the study found. For one such defect, spina bifida, the risk more than doubled.
The researchers also detected increased chances of heart defects, cleft lip and palate, water on the brain and problems in the growth of arms and legs.
There were hints the same may hold true for overweight women too but the data did not turn up enough evidence for the team to reach any firm conclusions.
Researchers stressed that because birth abnormalities affect only about two to four percent of pregnancies, the absolute risk for obese women remains low.
"Obesity increases the risk of many pregnancy complications, and this article further clarifies that obesity impacts the risk of birth defects, especially neural tube defects and congenital heart defects," said Loralei Thornburg of the University of Rochester Medical Center in New York, who was not involved in the study.
The World Health Organization classifies around 400 million people around the world as obese, including 20 million under the age of five, and the number is growing.
Obesity raises the risk of diseases such as type 2 diabetes, heart problems and is a health concern piling pressure on already overburdened national health systems.
Recent research has tied weight to other problems during pregnancy. A team from the Rand Corp think tank in California reported in 2008 that women who get pregnant after weight-loss surgery tend to be healthier and less likely to deliver a baby born with complications compared to obese women.
Further study may show how obesity may cause these problems, Judith Rankin, a Newcastle University researcher who worked on the study, said in a telephone interview.
"Women who are thinking about trying for a baby need to check their own weight first and then think about seeking help if they are overweight," Rankin said.
Reporting by Michael Kahn; Editing by Maggie Fox