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Babies born by planned caesarean section are up to four times more likely to suffer from breathing problems in the first days of life reported four newspapers (12th December 2007). These provided generally accurate summaries of a well-conducted cohort study that looked at the relationship between method of delivery and breathing difficulties in newborns.

Four newspapers (1-4) on 12th December 2007 reported that babies born by planned caesarean section are up to four times more likely to suffer from breathing problems than babies born by other methods.
The reports are based on a prospective cohort study of 34,458 births in a single hospital in Denmark between 1998 and 2006.(5) The study found that, at 37 weeks' gestation, the risk of breathing difficulties was around 3.7 times greater in babies born by elective caesarean section than those born by vaginal delivery or emergency caesarean section. This risk was three times greater at 38 weeks and around 1.9 times greater at 39 weeks. However, there was no statistically significant difference between the groups at 40 weeks gestation.
The newspapers generally provided accurate reports of the study. The Guardian article (3) also explained that the study did not investigate whether there were any long-term effects on the children.

Evaluation of the evidence base for the risk of respiratory morbidity in term infants delivered by caesarean section

Where does the evidence come from?

The research was conducted by Dr Anne Kirkeby Hansen and colleagues from Aarhus University Hospital, Denmark.

What were the authors' objectives?

To investigate the relationship between elective caesarean sections and respiratory morbidity in newborns.

What was the nature of the evidence?

The evidence came from a prospective cohort study of 34,458 liveborn babies without malformations, with gestational ages between 37 and 41 weeks. Data were collected from the beginning of 1998 to the end of 2006 in a single hospital. Expectant mothers completed a questionnaire early in the second trimester on various medical and other factors, including smoking, alcohol use, marital status, educational level and occupation. Information on newborns' respiratory health was obtained from routine discharge registration forms and a coding sheet completed by specialists.

What were the factors of interest?

Deliveries were categorised into two groups: elective caesarean section, or intended vaginal delivery (which included both vaginal deliveries and emergency caesarean sections).

The authors analysed the association between type of delivery and respiratory morbidity (which consisted of any respiratory distress, transient tachypnoea, and persistent pulmonary hypertension). The statistical analyses were also adjusted for other potential risk factors, such as maternal age, smoking history, alcohol intake, years of schooling, body mass index (BMI), parity and marital status.

What were the findings?

Of the 34,458 babies born during the study period, 2,687 (7.8%) were delivered by elective caesarean section. The remaining 92.2% of women were categorised as having intended vaginal delivery.

After adjusting for other factors, the risk of respiratory morbidity was around 3.7 times greater in the elective caesarean group than in the intended vaginal delivery group at 37 weeks gestation, three times greater at 38 weeks and around 1.9 times greater at 39 weeks. There was no significant difference between the two groups at 40 weeks gestation. The overall risk of respiratory morbidity for elective caesarean section was 4.2%.

A similar pattern of results were seen when the analyses were repeated in low-risk newborns alone and when the outcome was limited to serious respiratory morbidity.

What were the authors' conclusions?

The authors concluded that, compared with newborns delivered vaginally or by emergency caesarean section, those delivered by elective caesarean section around term have an increased risk of overall and serious respiratory morbidity. They also concluded that the relative risk increased with decreasing gestational age.

How reliable are the conclusions?

The conclusions are based on a well conducted prospective cohort study. Given the non-randomised nature of the study, there is the potential for unknown factors to have influenced the findings. However, attempts were made to take into account this potential for confounding by incorporating risk factors other than caesarean section into the analysis.

The authors' conclusions appear appropriate given the evidence presented, though it should be noted that the study did not investigate any relationship between elective caesarean section and children's respiratory health after discharge from the hospital neonatal department.

Systematic reviews

Information staff at CRD searched for systematic reviews relevant to this topic. Systematic reviews are valuable sources of evidence as they locate, appraise and synthesize all available evidence on a particular topic.

There were no related systematic reviews identified on the Cochrane Database of Systematic Reviews (CDSR) and none on the Database of Abstracts of Reviews of Effects (DARE).