A potential correlation between pre-labour caesarean delivery (PLCD) and acute lymphoblastic leukaemia (ALL) could offer new targets for cancer prevention research, according to new research from the Masonic Cancer Center, University of Minnesota.
The study is published in the current edition of the journal The Lancet Haematology.
Researchers were led by Masonic Cancer Center members Erin Marcotte, Ph.D., assistant professor, and Logan Spector, Ph.D., professor, of the Division of Epidemiology and Clinical Research in the Department of Paediatrics at the University of Minnesota Medical School.
The pooled analysis covered 13 studies, using data from the Childhood Leukaemia International Consortium (CLIC).
The analysis looked at 33571 subjects overall, including 23351 control subjects and 8655 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).
There was also no observed correlation between AML and pre-labour caesarean delivery.
However, the analysis showed a 23% increase in risk of ALL in children born by 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 Marcotte.
"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."
The reason for the increased risk of ALL with pre-labour caesarean delivery is not known.
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. We believe further investigation into this cortisol mechanism link is warranted due to these findings."
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.
They believe further investigation into this study's findings is needed, utilising more detailed and reliable delivery information.
"This association deserves a closer look to better determine what's behind the link," said Spector.
"Cortisol exposure is plausible since similar compounds are used to treat ALL. 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-leukaemic cells."
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