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Antibiotics during pregnancy increases risk of childhood obesity

Delivery by caesarean section also leads to increased obesity risk

Ingrid Torjesen

Wednesday, 19 November 2014

Children exposed to antibiotics in the second or third trimester of pregnancy have a higher risk of childhood obesity at age 7, US researchers have found.

Babies who were delivered by a caesarean section also had a higher risk of obesity, according to the study* published online in the International Journal of Obesity.

Previous studies have shown that antibiotics administered early in life may be associated with increased risk of obesity in childhood, but this is the first study reporting that maternal antibiotic use in the second or third trimester of pregnancy increases the risk of obesity in the child born.

Antibiotics affect microbes in the mother and may enter foetal circulation via the placenta. Bacteria that inhabit the colon have important roles in maintaining our health and imbalances in these bacterial populations can cause a variety of illnesses. Researchers believe that disturbances in the normal transmission of bacteria from mother to child could place the child at risk for several health conditions, including obesity.

The findings are based on data from 436 mothers and their children who were followed until 7 years of age. The women were healthy non-smokers recruited for the Northern Manhattan Mothers and Children Study from prenatal clinics at New York-Presbyterian Hospital and Harlem Hospital Center between 1998 and 2006.

Sixteen per cent of the mothers had taken antibiotics in the second or third trimester of pregnancy. Their children had an 84 per cent higher risk of obesity, compared with the children whose mothers had not taken antibiotics.

Noel Mueller, postdoctoral research fellow at Columbia University's Mailman School of Public Health and Institute of Human Nutrition, said that although the results needed to be replicated they suggested “new mechanisms through which childhood growth trajectories are influenced at the earliest stages of development”.

However, he emphasised: “Our findings should not discourage antibiotic use when they are medically needed, but it is important to recognise that antibiotics are currently overprescribed."

Delivery by caesarean section was also found to be associated with a 46 per cent higher risk of childhood obesity. Unlike with some previous studies, the risk was higher regardless of whether the procedure was elective or non-elective.


* N T Mueller, et al. Prenatal exposure to antibiotics, cesarean section and risk of childhood obesity. International Journal of Obesity , November 2014. doi:10.1038/ijo.2014.180.

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