CHMP senior fellow Meg Olmert is author of Made for Each Other: The Biology of the Human–Animal Bond.
The vast majority of our babies are born in hospitals and delivered by medical professionals. Childbirth has become a medical procedure that involves the regular use of synthetic oxytocin to induce labor contractions and analgesics to reduce the pain. Anesthesia is given to the 30% of mothers whose babies are delivered by C-section. Elective C-section—which is performed before the start of labor—is one of the most rapidly increasing surgical procedures. It’s only recently that wisdom and the long-term public health consequences of the medicalization of childbirth have been called into question.
In the mid-1990s researchers in Sweden began investigating the effects of C-section surgery on mothers. It was well known that mothers who had C-section surgery had difficulty breastfeeding. It was also well known that oxytocin, a brain hormone, is responsible for the release of breast milk and the instigation of labor contractions. Epidurals and anesthesia reduce levels of oxytocin in mothers, while surgical delivery eliminates the passage through the birth canal that powerfully triggers oxytocin production in the brain of baby and mother. By comparing blood samples the researchers found that women who delivered by C-section had weaker oxytocin pulses during breastfeeding than mothers who delivered vaginally. The vaginal-delivery mothers also produced more breast milk and reported feeling less anxious and more interested in interacting with those around them than the C-section mothers.
This tracks well with our new realization of oxytocin’s ability to promote maternal and social bonding, our capacity to cope with stress, and fight disease. We also now understand that these social and biological oxytocin advantages are passed from mother to infant during natural childbirth and through high quality, stable maternal care.
Another study comparing babies born by vaginal delivery and C-section showed that vaginally delivered babies were less reactive to pain. Just last month, a team of researchers showed, in rats, that oxytocin released during labor acts as a natural pain-killer. This analgesic effect may have long term consequences on perception of physical and perhaps psychic pain for the rest of our lives. Surgically bypassing the vaginal journey not only deprives the infant of the benefits of prenatal exposure to oxytocin; it prevents the baby from experiencing the massive sympathetic stress response that prepares the lungs for their first breath and activates the inflammatory defense system that will help it survive in the new world.
So, it’s not that surprising to learn that C-section is an established risk factor for later development of asthma and allergy, type 1 diabetes mellitus, childhood leukemia and testicular cancer. In 2009, another Swedish team investigated how C-sections might compromise the immune system of newborns. They analyzed the DNA of white blood cells extracted from umbilical cords of babies delivered by elective C-section and vaginal birth. The white blood cells of surgically delivered babies showed a significantly greater degree of “DNA methylation.” This means a methyl chemical group is added to a particular site of the genome, reducing access to the DNA and diminishing the chance that the gene will ever be activated. We now know that environmental influences—like how we are born or mothered—can exert this kind of dynamic effect on our DNA, resulting in long-term physiological, psychological, and behavioral consequences.
Future studies are needed to see if increased methylation of the DNA of white blood cells as a result of C-section is, in fact, silencing critical immune systems that are linked to the emergence of these common diseases. But even now, enough is known to give serious pause before a doctor recommends or a mother chooses elective Caesarean section.