Paediatric acute lymphoblastic leukaemia and caesarean section: A report from the United Kingdom Childhood Cancer Study (UKCCS)

Cohort profile: the United Kingdom Childhood Cancer Study (UKCCS) - a UK-wide population-based study examining the health of cancer survivors

PURPOSE

The United Kingdom Childhood Cancer Study's (UKCCS's) matched cohort was established to examine the longer term morbidity and mortality of individuals previously diagnosed with cancer before 15 years of age, comparing future healthcare patterns in 5-year cancer survivors to baseline activity seen in age- and sex-matched individuals from the general population.

PARTICIPANTS

Predicated on a national childhood cancer case-control study conducted in the early 1990s (4430 cases, 9753 controls) in England, Scotland and Wales, the case population comprises 3125 cancer survivors (>5 years), and the control population 7156 age- and sex-matched individuals from the general population who did not have cancer as a child. Participants are now being followed up via linkage to national administrative healthcare databases (deaths, cancers and secondary care hospital activity).

FINDINGS TO DATE

Enabling the creation of cohorts with minimal selection bias and loss to follow-up, the original case-control study registered all newly diagnosed cases of childhood cancer and their corresponding controls, regardless of their family's participation. Early findings based on the registered case population found marked survival variations with age and sex across subtypes and differences with deprivation among acute lymphoblastic leukaemia (ALL) survivors. More recently, comparing the health-activity patterns of the case and control populations revealed that survivors of childhood ALL experienced excess outpatient and inpatient activity across their teenage/young adult years. Adding to increased risks of cancer and death and involving most clinical specialties, excesses were not related to routine follow-up monitoring and showed no signs of diminishing over time.

FUTURE PLANS

With annual linkage updates, the UKCCS's maturing population-based matched cohorts provide the foundation for tracking the health of individuals through their lifetime. Comparing the experience of childhood cancer survivors to that of unaffected general-population counterparts, this will include examining subsequent morbidity and mortality, secondary care hospital activity and the impact of deprivation on longer term outcomes.

Association of cesarean section with risk of childhood leukemia: A meta-analysis from an observational study

Recent studies suggest that children born via cesarean section (CS) are predisposed to immune-mediated diseases later in life. The association between CS and childhood leukemia was investigated in this meta-analysis of observational studies. Two researchers independently searched PubMed, Web of Science, Embase, and Cochrane Library for literature on the association between CS and childhood leukemia before February 2022. And pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated to determine the link between CS and childhood leukemia. The preliminary search resulted in 1321 articles and 16 articles were finally included after screening. The primary outcome was the risk of leukemia in children born via CS versus those born vaginally. The results revealed that having a CS was associated with an increased risk of childhood leukemia compared to having vaginal section (VS) (OR = 1.07, 95% CI: 1.02-1.13, p = 0.01), especially for acute lymphoblastic leukemia (ALL) (OR = 1.09, 95% CI: 1.03-1.16, p = 0.004). Children delivered via elective CS had a higher risk of ALL (OR = 1.18, 95% CI: 1.07-1.31, p = 0.001), but emergency CS did not. It is worth noting that neither emergency CS nor elective CS were found to be associated with acute myeloid leukemia. Compared to VS, CS increased the risk of leukemia in children, with elective CS significantly increasing ALL risk.

Disquiet concerning cesarean birth

Cesarean birth has increased substantially in many parts of the world over recent decades and concerns have been raised about the propriety of this change in obstetric practice. Sometimes, a cesarean is necessary to preserve fetal and maternal health. But in balancing the risks of surgical intervention the implicit assumption has been that cesarean birth is an equivalent alternative to vaginal birth from the standpoint of the immediate and long-term health of the fetus and neonate. Increasingly, we realize this is not necessarily so. Delivery mode per se may influence short-term and abiding problems with homeostasis in offspring, quite independent of the indications for the delivery and other potentially confounding factors. The probability of developing various disorders, including respiratory compromise, obesity, immune dysfunction, and neurobehavioral disorders has been shown in some studies to be higher among individuals born by cesarean. Moreover, many of these adverse effects are not confined to the neonatal period and may develop over many years. Although the associations between delivery mode and long-term health are persuasive, their pathogenesis and causality remain uncertain. Full exploration and a clear understanding of these relationships is of great importance to the health of offspring.

Are there adverse outcomes for child health and development following caesarean section delivery? Can we justify using elective caesarean section to prevent obstetric pelvic floor damage?

INTRODUCTION AND HYPOTHESIS

Elective pre-labour Caesarean section (CS) delivery is widely regarded as the panacea for all pelvic floor dysfunction despite substantial epidemiological evidence that it is only partially protective. To demand a CS is also considered a right for the well-counselled patient, even without an elevated risk of incontinence or prolapse. In recent years there has been increasing data on possible adverse health outcomes for children delivered by CS over those delivered vaginally. This includes respiratory illness, atopic conditions, obesity, diabetes and other severe auto-immune diseases. Concern has also been raised over possible impacts on cognitive and neuropsychological development in these children. Often the response has been to dismiss these outcomes as a result of the indication for the CS birth such as antenatal compromise or maternal disease. However the marked increase in non-medical Caesarean delivery throughout many regions of the world has allowed us to better distinguish these contributing factors.

METHODS

This narrative review looks at some of the more recent evidence on adverse health and developmental outcomes associated with CS, particularly pre-labour CS and the implications for the long term health of our society.

RESULTS

Epidemiological studies and animal research indicate an increased risk of negative impacts on child physical health and neuro-cognitive development aftercaesarean section delivery, particularly pre-labour Caesarean section, compared with vaginal delivery. This elevated risk persists after correction forobstetric and maternal factors.

CONCLUSION

Caesarean section delivery can result in adverse outcomes for infant, maternal and societal wellbeing. Elective Caesarean section, purely to potentially minimise pelvic floor dysfunction, cannot be justified.

Cesarean Section Is Associated with an Increased Risk of Acute Lymphoblastic Leukemia and Hepatoblastoma in Children from Minnesota

BACKGROUND

In recent decades, Cesarean section (C-section) rates have increased. C-section is hypothesized to negatively impact the developing immune system by altering activation of the hypothalamic-pituitary-adrenal axis and the infant microbiome, among other mechanisms, thereby potentially modulating childhood cancer risk.

METHODS

Using linked birth and cancer registry data from Minnesota (1976-2014), we included individuals ages 0-14 at diagnosis with one of 19 cancers. Cases and controls were frequency matched by birth year. We used logistic regression to estimate ORs and 95% confidence intervals (95% CI) as the measure of association between C-section and cancer. We assessed sex-C-section interactions for each cancer and conducted stratified analyses in acute lymphoblastic leukemia (ALL) for birth year, age at diagnosis, and maternal race.

RESULTS

There were 3,166 cases and 20,589 controls. One third (n = 1,174) of controls born during 2004-2014 were delivered via C-section compared with 42.2% of cases (n = 285). C-section was associated with ALL (n = 819; OR: 1.20; 95% CI: 1.01-1.43) and hepatoblastoma (n = 50; OR: 1.89; 95% CI: 1.03-3.48), particularly among females (ALL OR: 1.34; 95% CI: 1.04-1.72; hepatoblastoma OR: 3.87; 95% CI: 1.30-11.57). The risk of ALL was highest during 2005-2014 (OR: 1.62; 95% CI: 1.11-2.34) and among children ages 1-5 years (OR: 1.28; 95% CI: 1.02-1.61).

CONCLUSIONS

C-section was associated with an increased risk of ALL and hepatoblastoma.

IMPACT

These associations require investigation to determine causality and rule out confounding by indication or reverse causality. The mechanisms underlying these associations may depend on neonatal immune system processes altered during C-section deliveries.

Paediatric acute lymphoblastic leukaemia and caesarean section: A report from the United Kingdom Childhood Cancer Study (UKCCS)

BACKGROUND

Reports have suggested that children born by caesarean initiated before labour onset may be at increased risk of developing acute lymphoblastic leukaemia (ALL). However, with most data being derived from case-control study interviews, information on the underpinning reasons for caesarean section is sparse, and evidence is conflicting.

OBJECTIVES

Use clinical records compiled at the time of delivery to investigate the association between childhood ALL and caesarean delivery; examining timing in relation to labour onset, and reasons for the procedure.

METHODS

Data are from the UK Childhood Cancer Study, a population-based case-control study conducted in the 1990s, when caesarean section rates were relatively low, in England, Scotland, and Wales. Children with ALL were individually matched to two controls on sex, date of birth, and region of residence. Information on mode of delivery and complications was abstracted from obstetric records. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using logistic regression models adjusted for matching variables and relevant covariates.

RESULTS

Around 75% of the 1034 cases and 1914 controls were born through unassisted vaginal delivery. Caesarean delivery was as frequent in cases and controls (OR 1.07, 95% CI 0.84, 1.36). No association was observed between ALL and caesarean delivery either during or before labour, with adjusted ORs of 1.08 (95% CI 0.78, 1.48) and 1.09 (95% CI 0.78, 1.53), respectively. For B-cell ALL, the ORs were 1.14 (95% CI 0.81, 1.59) for caesarean during labour and 1.21 (95% CI 0.85, 1.72) for prelabour. The underpinning reasons for caesarean delivery differed between cases and controls; with preeclampsia, although very rare, being more common amongst cases born by caesarean (OR 8.91, 95% CI 1.48, 53.42).

CONCLUSIONS

Our obstetric record-based study found no significant evidence that caesarean delivery increased the risk of childhood ALL, either overall or when carried out before labour.