Planned C-sections linked to leukaemia risk in children

Children born by planned caesarean section may face a 21 per cent higher risk of developing acute lymphoblastic leukaemia (ALL) later in life, new research has found.

The risk was even higher for B-cell acute lymphoblastic leukaemia (B-ALL) – the most common form of childhood blood cancer – with a 29 per cent increased risk compared to children born vaginally. The elevated risk appeared more pronounced in boys and in younger children.

Despite the findings, researchers stressed that childhood leukaemia remains rare. In Sweden, between 50 and 70 children are diagnosed with B-ALL each year. The excess risk associated with planned C-sections corresponds to approximately one additional case annually.

The study, led by researchers at Karolinska Institutet, examined data from nearly 2.5 million children born in Sweden between 1982 and 1989, and from 1999 to 2015. Of these, around 15.5 per cent – approximately 376,000 children – were delivered by caesarean section. In the entire cohort, 1,495 children were later diagnosed with leukaemia.

ALL is a cancer of the blood that affects white blood cells. B-ALL specifically affects B-lymphocytes, a type of immune cell that plays a role in fighting infection.

Using the Medical Birth Register, researchers were able to distinguish between planned and emergency caesarean sections. The increased risk was observed only among those born by planned C-section. The association remained even after adjusting for other relevant factors in mothers and children.

Christina-Evmorfia Kampitsi, researcher at the Institute of Environmental Medicine at Karolinska Institutet and lead author of the study, said: “C-sections are an important and often life-saving part of obstetric care. We don’t want mothers to feel anxious about medically indicated C-sections. But when this result is combined with other study results showing that the risk of later asthma, allergies or type 1 diabetes increases in children born by planned C-section, there is reason to discuss C-sections that are not medically indicated.

Researchers suggest the difference in risk between planned and emergency C-sections may be related to how the baby is exposed to stress and bacteria at birth. Emergency caesareans often begin as vaginal deliveries, meaning the baby may experience birth-related stress and be exposed to vaginal bacteria if the amniotic sac has ruptured.

In contrast, planned C-sections are typically performed before labour starts, reducing exposure to maternal bacteria and stress, which may affect immune system development and help explain the increased risk.

Some results did not reach the threshold for statistical significance, meaning chance cannot be entirely ruled out. Kampitsi said: “Fortunately, ALL is rare. This means that many C-deliveries are needed to obtain a statistically significant result, and it is difficult to obtain such a large sample in a Swedish registry study. However, the results are close to significant, are in line with what previous studies have shown, and remain when we adjust for other relevant factors, which still makes them relevant.”

The findings may help improve understanding of the causes of childhood leukaemia and add to growing evidence of associations between planned C-sections and immune-related conditions.

The research was funded by the Swedish Research Council and the Swedish Cancer Society. The researchers reported no conflicts of interest.