Planned C-sections linked to slight increase in childhood leukaemia risk, a new study suggests

The researchers found that the risk of developing the most common form of leukaemia (acute lymphoblastic leukaemia, or ALL) was 21% higher in children born by planned C-section than in children born vaginally or by emergency C-section.

The risk was also higher in boys than in girls, and was concentrated in children up to five years old.

It’s important to note that the risk is still low, even if 21% sounds high. Between 50 and 70 Swedish children are diagnosed with the most common form of ALL each year, and that 21% higher risk corresponds to only one more case per year, the researchers wrote in a press release.

Why does a planned C-section increase a child's risk of cancer?

During a vaginal birth, babies get exposed to bacteria as they move through the vaginal canal. These bacteria can help build up their immune system and gut microbiome (the ecosystem of microorganisms that live in your gut and help with digestion). Babies also experience stress as they come out in a vaginal delivery, which releases stress hormones that help to regulate their immune systems.

Babies born by planned C-section don’t tend to come into contact with the vaginal canal, so aren’t exposed to the bacteria there, and don’t go through the same stress.

Emergency C-sections, however, usually start out as vaginal deliveries, and so babies are mostly exposed to the same stress and bacteria as babies born via a vaginal birth.

The researchers suggest that it could be these differences that contribute to children who are born via planned C-section having a higher risk of developing certain cancers later in life.

But they also note that the correlation could be because planned C-sections are more likely to be the result of pregnancy complications like diabetes or preeclampsia, maternal conditions like advanced age or obesity, or birth defects. So it could be these things that increase the risk of leukaemia, rather than the C-section itself.

You don’t need to worry — but maybe reconsider a non-medically necessary C-section

The researchers say that their findings add to a growing amount of evidence that non-medically necessary C-sections could lead to potentially negative outcomes for children in the long term.

For example, “the risk of later asthma, allergies, or type 1 diabetes increases in children born by planned C-section,” says Christina-Evmorfia Kampitsi, the lead author of the study.

But overall, ALL is a rare disease, so the risks of developing it are very small. And some of the results the researchers found weren’t statistically significant, meaning that they could be down to chance rather than patterns in the data

When C-sections are ‘medically indicated,’ or deemed medically necessary, the risk of a child getting cancer later in life isn’t as pressing as the immediate risk to them and their mothers.

“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," Christina says.

The takeaway

If you’ve had a planned C-section, or have one scheduled, there’s no cause for alarm. The vast majority of babies born this way grow up healthy, and the benefits of a medically necessary C-section far outweigh the small statistical increase in risk found in this study.

But as more research sheds light on how birth choices affect long-term health, this study does underline the importance of weighing the pros and cons carefully – particularly in cases where a planned C-section is elective rather than essential.

As always, the best person to guide you is your midwife or consultant, and this latest study is a reminder that personalised, evidence-based care matters more than ever.

Read more:

• Caesarean dos and don’ts
• Who decides whether you have a caesarean section?
• Real births: 9 months of sickness, gestational diabetes and an elective caesarean