Swedish doctors have analyzed data from millions of children and confirmed that those born via planned surgical delivery have a higher likelihood of developing acute lymphoblastic leukemia, according to Naked Science.

An increasing number of women worldwide are opting for cesarean section (C-section) deliveries without medical necessity. This trend is concerning to healthcare professionals due to the potential adverse outcomes for both mother and child. Previous studies have offered mixed results regarding an elevated risk of acute lymphoblastic leukemia (ALL) in children born through planned C-section.

A team of epidemiologists and pediatric oncologists from the Karolinska Institute in Sweden decided to explore the possible link between birth method and childhood leukemia using a large sample. Their study, published in The International Journal of Cancer, examined data on nearly 2.5 million Swedish children born between 1982–1989 and 1999–2015. Information on pregnancy details, delivery type, children's health, and cancer diagnoses was obtained from national registries.

Of the children included in the sample, nearly 376,000 (15.5%) were born via C-section. Leukemia was diagnosed in 1,495 children from the entire group.

The higher risk of childhood leukemia in children born via planned C-section remained even after adjusting for other maternal and child-related factors. The greatest risk was observed in boys under the age of five. Notably, no association was found between emergency C-sections and an increased risk of acute lymphoblastic leukemia.

Despite this observed trend, the researchers emphasized that the excess leukemia risk linked to planned C-section is relatively small—approximately one additional case of acute B-cell lymphoblastic leukemia per year. According to experts, 50–70 children are diagnosed with this form of cancer annually in Sweden.

“Cesarean section is an important part of obstetric care and often life-saving. We do not want to unnecessarily alarm mothers who require the procedure for medical reasons,” said lead author Christina-Evmorfia Kampitsi. However, she added that when it comes to elective C-sections without clear medical indications, the findings—along with previous data linking C-section birth to asthma, allergies, and type 1 diabetes—raise important questions about the necessity of the procedure.

The researchers also discussed potential mechanisms that might explain why planned, but not emergency, C-sections are associated with an increased risk of certain immune-related conditions.

They suggest that emergency C-sections are typically preceded by the onset of labor. During this process, the fetus experiences stress and is exposed to the mother's vaginal bacteria as the amniotic sac breaks—experiences that do not occur during a planned C-section. According to the team, further research is needed to better understand the factors contributing to the development of leukemia in children.