Intended for healthcare professionals


Risk of respiratory morbidity in term infants delivered by elective caesarean section: cohort study

BMJ 2008; 336 doi: (Published 10 January 2008) Cite this as: BMJ 2008;336:85
  1. Anne Kirkeby Hansen, research fellow1,
  2. Kirsten Wisborg, staff specialist2,
  3. Niels Uldbjerg, professor3,
  4. Tine Brink Henriksen, associate professor2
  1. 1Perinatal Epidemiology Research Unit, Aarhus University Hospital, Brendstrupgaardsvej 100, Skejby, 8200 Aarhus N, Denmark
  2. 2Department of Paediatrics, Aarhus University Hospital
  3. 3Department of Obstetrics and Gynaecology, Aarhus University Hospital
  1. Correspondence to: A K Hansen AKH{at}
  • Accepted 4 November 2007


Objective To investigate the association between elective caesarean sections and neonatal respiratory morbidity and the importance of timing of elective caesarean sections.

Design Cohort study with prospectively collected data from the Aarhus birth cohort, Denmark.

Setting Obstetric department and neonatal department of a university hospital in Denmark.

Participants All liveborn babies without malformations, with gestational ages between 37 and 41 weeks, and delivered between 1 January 1998 and 31 December 2006 (34 458 babies).

Main outcome measures Respiratory morbidity (transitory tachypnoea of the newborn, respiratory distress syndrome, persistent pulmonary hypertension of the newborn) and serious respiratory morbidity (oxygen therapy for more than two days, nasal continuous positive airway pressure, or need for mechanical ventilation).

Results 2687 infants were delivered by elective caesarean section. Compared with newborns intended for vaginal delivery, an increased risk of respiratory morbidity was found for infants delivered by elective caesarean section at 37 weeks’ gestation (odds ratio 3.9, 95% confidence interval 2.4 to 6.5), 38 weeks’ gestation (3.0, 2.1 to 4.3), and 39 weeks’ gestation (1.9, 1.2 to 3.0). The increased risks of serious respiratory morbidity showed the same pattern but with higher odds ratios: a fivefold increase was found at 37 weeks (5.0, 1.6 to16.0). These results remained essentially unchanged after exclusion of pregnancies complicated by diabetes, pre-eclampsia, and intrauterine growth retardation, or by breech presentation.

Conclusion Compared with newborns delivered vaginally or by emergency caesarean sections, those delivered by elective caesarean section around term have an increased risk of overall and serious respiratory morbidity. The relative risk increased with decreasing gestational age.


  • Contributors: AKH conceived and designed the study, analysed and interpreted the data, and drafted the article. She is guarantor. KW and NU interpreted the data and revised the article. TBH conceived and designed the study, interpreted the data, and revised the article. All authors approved the final version.

  • Funding: This study was supported by the Clinical Institute, Aarhus University, the Research Initiative, Aarhus University Hospital, and Aase and Einer Danielsens Fund.

  • Competing interests: None declared.

  • Ethical approval: Not required.

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

  • Accepted 4 November 2007
View Full Text