Catherine and other colleagues from Britain's New Castle 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, spinal bifida, the risk more than doubled. The researchers also detected increased chances of heart defect, cleft lip and palate, water on the brain and problems in the growth of arms and legs. The World Health Organization classifies around 400 million people around the world as obese, including 20 million under the age of 5, and the number is growing. Obesity raises the risks of diseases such as type II diabetes, heart problems and is a health concern piling pressure on an already overburdened national health system. Recent research has tight weight to other problems during pregnancy. A team from the Round Corporation 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. Juliet at New Castle 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.