A recent study published in The BMJ, a popular medical journal, has found that maternal obesity significantly increases the risk of having a child born with Birth Defects. It has long been known that a Mother's weight is correlated to her child's health, however, this research takes it one step further as it takes a closer look at congenital defects and how their likelihood is affected by having a mother who obese in comparison to one who is overweight.

Expanding on old knowledge

The most recent research on this topic was lead by Dr. Martina Persson, an epidemiologist at the Karolinska Institute in Stockholm, Sweden.

The connection between maternal weight and the likelihood of having a baby born with a Congenital Defect was already known when she began her investigation but older studies failed to identify whether there was any difference in the risks for obese mothers compared to overweight mothers.

For more than a decade, Persson and her team collected and analyzed data from more than 1.2 million live births, making distinctions between overweight mothers and obese mothers. For each birth the mother was classified as either underweight, of a normal weight, overweight or obese using the BMI scale, a measurement tool that relates a person's height and weight. A woman was considered underweight if her BMI was less than 18.5, of a normal weight if her BMI was 18.5 - 24, and overweight if her BMI was between 25 and 29.

Mothers with a BMI of more than 29 fell into the obese category which was split into three different classes based on the severity. Class one included mothers with BMIs between 30-34. A mother was put into class two if her BMI was between 35-39, and class 3 if her BMI was 40 or greater.

The risk of birth defect varies with BMI

Just over 42,000 of the babies that were involved in this study were born congenital birth defects, amounting to 3.5% of total births. The defects observed in the study were found in body parts such as the heart, limbs, and genitals as well as the urinary, digestive, and nervous systems.

Only a small difference was seen between the rate of birth defects in mothers at a healthy weight and mothers who were considered overweight when their baby was born. 3.4% of mothers at a healthy weight had babies born with defects compared to 3.5% for mothers considered overweight.

The risk was significantly higher for mothers who were identified as obese and the risk of birth defect was found to be greater in mothers who were more severely obese. Mothers in the first class had a 3.8% chance of giving birth to a child with a congenital defect. Class two had a risk of 4.2% while class three had a risk of 4.7%. This research does not investigate why the risk increased with BMI.