A pooled analysis by researchers at Masonic Cancer Centre, University of Minnesota in US, which covered 13 studies, using data from the Childhood Leukaemia International Consortium (CLIC), has concluded that children born by pre-labour caesarean delivery may have a higher risk of developing acute lymphoblastic leukaemia (ALL) -- a cancer of the white blood cells.
The analysis looked at 33,571 subjects overall, including 23,351 control subjects and 8,655 cases of ALL. The analyses were controlled for a number of outside factors, including breastfeeding, parental education levels, and ethnicity. After looking most closely at deliveries where the reason for caesarean were available, no link was found between emergency caesareans and ALL or Acute myeloid leukaemia (AML).
However, the analysis showed a 23% increase in risk of ALL in children born by pre-labour caesarean delivery. There was also no observed correlation between AML and pre-labour caesarean delivery. “Our goal was to determine if there was an association between caesarean deliveries and ALL, to identify potential new targets for research into cancer prevention if there is a correlation,” said Erin Marcotte, assistant professor at University of Minnesota.
“While the link between overall caesarean delivery and childhood leukaemia was not statistically significant, it was notable to find an association between pre-labour caesarean delivery and ALL,” Marcotte said. The reason for the increased risk of ALL with pre-labour caesarean delivery is not known, researchers said.
Several mechanisms may be at play, including the stress response in the foetus caused by labour and the colonisation of microbiota a newborn experiences during a vaginal delivery that is missed during a caesarean birth. “The most plausible explanation for the association between ALL and pre-labour caesarean delivery is in the cortisol, or stress-related, mechanism,” said Marcotte.
“Because ALL is not associated with all caesarean deliveries, it seems less likely the microbiota colonisation is a significant factor in this phenomenon,” Marcotte said. Researchers note the strength of association in these findings is comparable to other studies looking at caesarean delivery rates and other childhood outcomes, including Type I diabetes and asthma.
“Cortisol exposure is plausible since similar compounds are used to treat ALL,” said Logan Spector, professor at the University of Minnesota Medical School. “We also know that some are born with cells that are on the path to becoming leukaemia. Thus, our working hypothesis is that cortisol exposure at birth may eliminate these pre-leukemic cells,” Spector said. The study was published in the journal The Lancet Haematology.