Research presented at the European Respiratory Society (ERS) congress on Sunday in Munich, Germany, found that prenatal exposure to antibiotics was associated with a slight increase in the incidence of asthma in toddlers.
The Dutch study looked at 1,228 children with asthma, and compared them with their own siblings who did not have the condition. Using siblings as a control group allowed for better comparison across pregnancies, as they had the same mother, said the researchers.
The study showed that toddlers whose mothers were prescribed antibiotics in their third trimester of pregnancy appeared to have a greater risk of developing asthma. Cases where women used antibiotics for longer were associated with an even greater risk.
There was no significant change in asthma incidence when mothers-to-be were prescribed antibiotics during their first or second trimester of pregnancy.
Lead author Dr Bianca Mulder, from the University of Groningen, Netherlands, said: ‘If we stratify the exposure to different trimesters, you can see that there is a slight increase in asthma risk when mothers use [antibiotic] medication during the third trimester of pregnancy.’
Dr Mulder said it was ‘logical’ that only treatment during the third trimester had an effect.
Bacteria from the mother’s vaginal tract colonise a child during birth. Altering the bacterial composition of the vagina with antibiotics during the third trimester – ‘the closest trimester to birth’ – could explain the increase in asthma incidence, Dr Mulder said.
The study found that one in five pregnant mothers received antibiotic treatment throughout their pregnancy.