New York, Nov 19 (IANS): Taking antibiotics in the second or third trimester of pregnancy may make your child obese at age seven, research shows.

"Our findings on prenatal antibiotics and risk for offspring obesity are novel, and thus warrant replication in other prospective cohort studies," said Noel Mueller from Columbia University.

"Our findings should not discourage antibiotic use when they are medically needed, but it is important to recognize that antibiotics are currently overprescribed," Mueller added.

Antibiotics affect microbes in the mother and may enter fetal circulation via the placenta.

Disturbances in the normal transmission of bacteria from the mother to the child are thought to place the child at risk for several health conditions, including obesity.

The researchers followed 436 mothers and their children until seven years of age.

Of these 436 children, 16 percent had mothers who used antibiotics in the second or third trimester.

The children exposed to antibiotics in this timeframe had an 84-percent higher risk of obesity, compared with children who were not exposed.

The researchers also found that independent of prenatal antibiotic usage, delivery by Caesarean section was also associated with a 46-percent higher risk of childhood obesity.

The researchers controlled subjects for maternal age, ethnicity, birth weight, sex, breastfeeding in the first year, and gestational antibiotics or delivery mode.

The findings were published online in the International Journal of Obesity.