Caesarean delivery can alter DNA: study

Researchers at Karolinska Institutet believe they have discovered the DNA mutations that explain why children delivered by planned Caesarean are at a higher risk for immunological diseases such as asthma, cancer and diabetes.

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The genetic makeup of white blood cells looks different in children delivered via Caesarean compared to that of children born normally, reports Svenska Dagbladet newspaper (SvD).

An explanation for the different DNA sequences might be that those delivered via Caesarean experience greater stress than babies delivered naturally.

While stress builds up gradually during normal birth, the nervous systems of babies delivered via Caesarean are exposed to sudden stress. At the same time, some DNA genes are turned off while others are switched on.

Professor and paediatrician Mikael Norman, one of the researchers involved in the study, explained that stress occurring during vaginal birth is positive and goal-oriented:

“During a Caesarean, the baby is totally unprepared. The stress comes all at once. There are animal experiments that show that negative stress can programme offspring, something that later can play a role in terms of risk of illness.”

The study at Karolinska focused on the white blood cells in the umbilical cords of Caesarean babies and found mutations in their genetic makeup. The researchers noted differences in DNA sequencing of babies delivered via Caesarean and those delivered normally during the first two days after birth.

“We believe it's a pioneering discovery that Caesarean birth can effect genetic makeup up. Previously, the discussions were about the short-term risk for the mother and child,” Norman told SvD.

“This is of an entirely different magnitude and is part of a new way of looking at the side effects of Caesarean birth.”

The Karolinska study is, on one hand, a result of a debate about the health effects of Caesarean delivery and, on the other, a result of the fact that Caesarean as a delivery method has increased from around 5 percent of births in 1973 to 17.5 percent in 2007.