Children born by planned cesarean section (C-section) may have an increased risk of developing acute lymphoblastic leukemia (ALL) later in life, according to a recent study published by Kampitsi et al in the International Journal of Cancer. Alhough the researchers did find an association, they emphasized that the overall cancer risk in this population remains low.
Study Methods and Results
The study included nearly 2.5 million children born in Sweden during two periods: 1982 to 1989 and 1999 to 2015. Of these periods, 15.5%—nearly 376,000—were born by C-section. In the entire group, 1,495 children later developed leukemia. Using the Medical Birth Register, the researchers were able to divide the C-sections into planned and emergency surgeries. The children who later developed leukemia were overrepresented in the group born by planned C-section.
In particular, the risk of the most common type of childhood leukemia, ALL, increased. The risk of ALL was 21% higher in children born by planned C-section compared with children born vaginally. The risk of developing the most common type of ALL, B-cell ALL, was 29% higher in those born by planned C-section. The increased risk remained even when the researchers adjusted for other relevant factors in mothers and children. The increased risk was more pronounced in boys than in girls and among younger children.
The researchers emphasized that the risk of developing childhood leukemia remains low, regardless of the mode of delivery. “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,” said lead study author Christina-Evmorfia Kampitsi, PhD, a researcher at the Institute of Environmental Medicine at Karolinska Institutet in Stockholm.
Potential Risk Factors
In their report, the researchers discussed possible mechanisms that could explain why it is planned—not emergency—C-sections that carry an increased risk of certain diseases, all of which are related to immunologic factors. Their reasoning is that emergency C-sections usually begin as a vaginal delivery. This causes stress for the baby and exposure to vaginal bacteria if the amniotic sac has ruptured. However, in planned C-sections, which are usually performed before labor has started naturally, the baby does not experience this stress and is not exposed to vaginal bacteria. The researchers suggest this difference may help to explain the increased risk of ALL and believe the study may contribute to a better understanding of what causes ALL in children.
Some of the results did not reach the threshold for statistical significance, the authors noted.
“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,” concluded Dr. Kampitsi.
Disclosure: The research was funded by the Swedish Research Council and the Swedish Cancer Society. For full disclosures of the study authors, visit onlinelibrary.wiley.com.
