A large new study has found that a cesarean birth increases the risk of the offspring being overweight or developing obesity in later life. The findings were published on February 26 in the journal PLOS ONE by researchers at the Imperial College of London in the United Kingdom.
The researchers note that, worldwide in the last two decades, the prevalence of obesity has increased markedly in children and adults, with the highest incidences reported in the USA (33.8%) and Scotland (30%). During the same period, a 100% increase in caesarean sections has occurred in England. The World Health Organization (WHO) recommends that the cesarean section rate should not exceed 15%; however many nations report higher rates, including China (60%), Brazil (47%), and England (23·8%). The study authors explain that adverse effects of a cesarean birth on the newborn immediately after birth are well-known. Among all modes of delivery, the procedure is linked with the highest rates of neonatal morbidity and mortality, with increased risk of a low 1-minute Apgar, respiratory distress, hypoglycemia and a prolonged stay in a neonatal intensive care unit (NICU). They note that controversy exists whether a cesarean birth increases the risk of adverse health effects in childhood, such as asthma, other allergic disorders, and type-1 diabetes. They add that some research has suggested a link between a cesarean birth and later-life obesity. A study conducted in North America, which assessed nearly 200,000 adolescents, reported that children born by cesarean section are 40% more likely to be overweight. However, other studies that examined the possibility of an association between a cesarean birth and adult obesity have been small and contradictory.
In view of the foregoing, the investigators conducted a systematic review and meta-analysis to identify any association between mode of delivery and offspring body mass index (BMI); they assessed the risk of overweight, and obesity in adulthood for offspring born by a cesarean section. They also attempted to determine if offspring age, gender and type of cesarean section had an effect on outcomes.
After developing a search strategy, the researchers conducted PubMed, Google Scholar, and Web of Science searches for any article published before March 31, 2012, together with references of any studies deemed relevant. Studies were included in the analysis if they reported birth characteristics and long-term offspring follow-up into adulthood. The accumulated data from relevant studies were extracted onto a data table for statistical analysis.
The investigators identified 35 studies from the search; 15 of those studies with a combined population of 163,753 were found to be suitable for inclusion in the meta-analysis. A comparison of all cesarean deliveries to vaginal birth found an average BMI difference was 0.44 kg/m2. The risk of overweight was 1.26; the risk of obesity was 1.22. No gender differences were found.
The authors concluded that a strong association exists between a cesarean section and increased offspring BMI, overweight, and obesity in adulthood. Inasmuch as the cesarean section rate is increasing worldwide, a need exists to determine whether this is causal, or due to confounding influences.
Take home message:
Multiple factors are involved in whether an individual will become overweight or obese in adulthood; thus, a cesarean birth is one of many risk factors, including genetics and lifestyle choices. Although some cesarean births may be unnecessary, the procedure is done under circumstances such as failure to progress in labor or fetal distress that precludes continued labor.