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Antibiotic exposure during pregnancy and childhood asthma: a national birth cohort study investigating timing of exposure and mode of delivery
  1. Cecilie Skaarup Uldbjerg1,
  2. Jessica E Miller2,3,
  3. David Burgner2,3,4,
  4. Lars Henning Pedersen5,6,
  5. Bodil Hammer Bech1
  1. 1 Department of Public Health, Research Unit for Epidemiology, Aarhus University, Aarhus, Denmark
  2. 2 Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia
  3. 3 Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia
  4. 4 Department of Paediatrics, Monash University, Clayton, Victoria, Australia
  5. 5 Department of Clinical Medicine and Biomedicine, Aarhus University, Aarhus, Denmark
  6. 6 Department of Obstetrics and Gynecology, Aarhus University Hospital, Aarhus, Denmark
  1. Correspondence to Cecilie Skaarup Uldbjerg, Department of Public Health, Research Unit for Epidemiology, Aarhus University, Aarhus 8000, Denmark; cecilie{at}


Objective To investigate whether antibiotic exposure during pregnancy was associated with childhood asthma and if this relationship was conditional on timing of exposure and mode of delivery.

Design A cohort study using multivariable logistic regression models adjusting for a priori defined confounders. Pregnant women were recruited from 1996 to 2002.

Setting The Danish National Birth Cohort.

Patients Of the 96 832 children in the cohort, 32 651 children were included in the study population.

Main outcome measure Parent-reported childhood asthma at 11 years.

Results A total of 5522 (17%) children were born to mothers exposed to antibiotics during pregnancy. In adjusted analyses, children born to exposed mothers had higher odds of asthma (OR 1.14, 95% CI 1.05 to 1.24). There was no association with antibiotic exposure in the first trimester (OR 1.02, 95% CI 0.83 to 1.26), but higher odds were observed for antibiotic exposure in the second to third trimester (OR 1.17, 95% CI 1.06 to 1.28), compared with unexposed children. The overall association between antibiotics during pregnancy and childhood asthma was only observed in vaginally born children (OR 1.17, 95% CI 1.07 to 1.28) but not in caesarean section born children (planned caesarean section: OR 0.95, 95% CI 0.66 to 1.37; caesarean emergency: OR 0.96, 95% CI 0.73 to 1.28). In exposed vaginally born children, the odds for childhood asthma requiring treatment during the preceding year were 34% higher (OR 1.34, 95% CI 1.21 to 1.49), compared with unexposed vaginally born children.

Conclusions Antibiotic exposure in mid-to-late pregnancy is associated with higher odds of childhood asthma in vaginally born children. Mode of delivery may modify the association.

  • epidemiology
  • adolescent health

Statistics from


  • Contributors CSU, LHP and BHB designed the study. CSU performed the analyses of the data. All authors contributed to the writing of the paper. BHB supervised the project.

  • Funding The Danish National Birth Cohort (DNBC) was established with a significant grant from the Danish National Research Foundation. Additional support was obtained from the Danish Regional Committees, the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Health Foundation and other minor grants. The DNBC Biobank has been supported by the Novo Nordisk Foundation and the Lundbeck Foundation. Follow-up of mothers and children have been supported by the Danish Medical Research Council (SSVF 0646, 271-08-08B39/06-066023, O602-01042B and 0602-02738B), the Lundbeck Foundation (195/04, R100-A9193), The Innovation Fund Denmark 0603-00294B (09-067124), the Nordea Foundation (02-2013-2014), Aarhus Ideas (AU R9-A959-13-S804), University of Copenhagen Strategic Grant (IFSV 2012) and the Danish Council for Independent Research (DFF – 4183-00594 and DFF – 4183-00152). The study was partially funded by the Health Research Fund of Central Denmark Region (project 490-79-5601). LHP is supported by the Health Research Fund of Central Denmark Region. JEM is supported by the DHB Foundation, Australia. DPB is supported by a National Health and Medical Research Council (Australia) Senior Research Fellowship (GTN1064629) and an Investigator Grant (GTN1175744). Research at Murdoch Children’s Research Institute is supported by Victorian Government’s Operational Infrastructure Support Program.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval The study was approved by the Danish Data Protection Agency ( 2015-57-0002).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement No data are available. The data from the study are not publicly available due to considerations for privacy and anonymity of the participants. The data were retrieved from the DNBC and were used under licence for the current study. All requests for data from the DNBC must include a research protocol to be submitted to the Danish Data Protection Agency (Datatilsynet).

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