An unprecedented new report looking at the biochemical mechanisms linked to birth and breastfeeding suggests that over-treatment in the delivery room is having lasting, harmful effects on both mothers and children.

Premature baby boy delivered by Caesarean section. (Photo: Steve Lovegrove/Shutterstock)

For the third year in a row, the Centers for Disease Control and Prevention reports that the number of women who give birth by Caesarean section in the United States is hovering at around one-third of births. That's a 60 percent increase in 15 years, and a public health crisis. Why hasn't the number budged? Last year, it seemed that every professional organization publicly agreed (the obstetricians here, the nurses here, and the nurse-midwives here) that this is a problem and took responsibility for their part. They blamed, in a word, over-treatment.

“If overtreatment is defined as instances in which an individual may have fared as well or better with less or perhaps no intervention, then modern obstetric care has landed in a deep quagmire,” write the authors of a forward to a new and unprecedented report, Hormonal Physiology of Childbearing: Evidence and Implications for Women, Babies, and Maternity Care. “Navigating out of that territory will be challenging.”

In practice, this over-treatment looks like maternity wards where most women are being induced into labor or given synthetic oxytocin to speed up labor, where even women who plan on having a “natural” birth are told that they aren't “allowed” to walk around or eat, and who often turn to an epidural for relief (from the labor or the hospital protocols, it's difficult to say), which necessitates more interventions. These don't always work; after hours of this and that, many women wind up in the operating room.

“If overtreatment is defined as instances in which an individual may have fared as well or better with less or perhaps no intervention, then modern obstetric care has landed in a deep quagmire.”

We now have hospitals in varied places—like northern New Jersey and Miami, Florida—where there are more Caesarean sections than vaginal births. And hundreds of hospitals around the country have banned vaginal birth after a Caesarean.

Why is this risky, costly trend persisting? It's a topic that many researchers and journalists (myself included) have investigated. The short answer is a combination of for-profit medicine, malpractice fears, and our cultural bias toward technology. Less covered, though, is what's going on in women's bodies when they are basically left alone.

For the new, 200-plus-page Hormonal Physiology of Childbearing report, Sarah Buckley, an Australian physician and researcher, surveyed more than 1,000 studies, both on humans and animals, to map out what's known—and what remains unstudied—about the biochemical mechanisms linked to birth and breastfeeding.

Childbirth Connection, the group behind the report (and now part of the National Partnership for Women and Families) organized the publication in such a way that you can read the meaty executive summary in under an hour, send the Pathway to a Healthy Birth booklet to your pregnant friend, or geek out on the full report.

Choose the last option and you'll be rewarded with such fascinating trivia as how, immediately after birth, a baby placed skin-to-skin on his mother hormonally stimulates her chest to warm up, which, studies show, regulates the baby's temperature better than the glass trays most hospitals use. Another: The placenta produces an enzyme to help the mother metabolize oxytocin, the primary driver of contractions, during labor so that it disappears from the bloodstream between contractions, preventing the receptors from becoming desensitized, which would weaken and stall labor.

Not only fascinating, the report presents evidence of how this physiology leads to healthier mothers and babies.

One of the report’s big takeaways is that the glass warming tray, the synthetic oxytocin, even the epidural—these staples of modern maternity care are all subbing for normal physiology, and failing to measure up. “The integration of literature in one place makes it striking that we are overconfident that we can do a good job mimicking normal biology,” says Katherine Hartmann, an associate dean and professor of obstetrics and gynecology at Vanderbilt University who co-wrote the report’s forward.

The glass warming tray, the synthetic oxytocin, even the epidural—these staples of modern maternity care are all subbing for normal physiology, and failing to measure up.

We tend to favor mechanical metaphors for human physiology, but the report maps out a complex sequence of hormonal systems—non-linear and interdependent on each other—that more resemble a ballet or symphony.

Studies suggest that a warm-up begins in the days and even hours before labor, when the mother's brain, uterus, and mammary glands up the number of receptors for opioids and hormones such as oxytocin and prolactin.

Oxytocin drives the contractions that guide the baby out and later the contractions that will shrink the uterus and stop it from bleeding. It also triggers beta-endorphins, which tweak a woman's state of consciousness (and her experience of fear and pain) during labor and flood the brain with a warm, fuzzy high following birth. The beta-endorphins in turn stimulate prolactin, which starts circulating during labor in preparation for the suckling newborn, who further stimulates its release.

The baby's body is an active participant in this complicated feedback loop, and the mother's and baby's systems play off of one another. In the throes of labor, for example, the fetus has a “catecholamine surge” of adrenaline and non-adrenaline to shield its brain from trauma and prime the lungs to breathe.

After birth, the baby's brain produces a flood of oxytocin, which likely sustains a calm alertness and readiness for the breast, which in turn stimulates the mother's prolactin and oxytocin, which activate the reward centers in her limbic brain (the non-thinking part), “imprinting pleasure with infant contact and care,” Buckley writes.

Buckley makes a formidable case against interrupting this choreography. The mechanisms that protect both mother and baby kick into gear just before spontaneous labor—animal studies suggest big changes even in the hours before labor. So, for example, if we induce labor or schedule a Caesarean, we interfere with the oxytocin-prolactin response, which helps to explain why women who've ha d Caesarean often have more trouble breastfeeding.

Babies born by scheduled Caesarean without labor also don't get the protective catecholamine surge or a flood of oxytocin, which some speculate could have an impact on the oxytocin receptor function, implicated in conditions like autism.

Buckley calls the hours of childbirth a period of “heightened sensitivity” and epigenetic imprinting, influencing how genes express themselves. “What we know from really solid animal research is that what happens in the newborn period has major impacts,” Buckley says. “We should be concerned about human babies being exposed to non-physiological things in labor and birth. When we add that dimension to our considerations, it's very sobering. The truth is, we don't know the impacts of what we're doing.”

A team of obstetricians performing a Caesarean section in a modern hospital. (Photo: Salim Fadhley/Wikimedia Commons)

That imprinting is greatly important for the mother as well. Buckley explains how labor and childbirth turn on “the reward and motivation circuits in the mother's brain.” She mentions a study comparing women who’d had scheduled Caesareans (without labor) and women who'd had spontaneous vaginal births. Researchers gave the women MRI scans during the first month postpartum while they listened to recordings of their baby's cries. In the women who'd had vaginal births, the brain's reward centers lit up—the centers of motivation, empathy, alertness, and pleasure—while those areas were less activated in the women who'd had Caesareans.

Buckley is careful to say that a physiological birth isn't predictive of good mothering—we can bond with our thinking brain as well—but the reward circuitry set in motion “makes mothering a lot easier.”

This may be the most striking finding of all: The science suggests that mothering should feel great. But so many women have trouble breastfeeding, so many women feel exhausted and depressed and isolated and anxious. Surely part of this is culture, but is part of it also hormonal? Or, rather, is part of the problem that we're not getting our rightful share of feel-good hormones?

Decisions about whether to medically intervene in normal childbirth should ideally weigh risks versus benefits, but rarely do clinicians consider the hormonal benefits of not intervening, because until now they haven't been clearly documented. These findings should not only influence what goes on in labor and delivery wards but also how we do research and what we consider to be a satisfactory outcome.

“I hope this report will be a reminder for what a lot of us feel in our gut, which is that we should be doing less,” Hartmann says. “I think people have been hesitant to claim any part of birth as a sort of women's empowerment thing for reasons that maybe we don't want to equate reproductive function with power. But it's a very powerful experience, and for folks to not get to have it because we have so much technology in the way seems to me a big disappointment.”

Among the report's recommendations are to “provide prenatal care that reduces stress and anxiety,” “foster privacy” and a low-stress birth environment with freedom from cumbersome medical equipment, and not separate mother and newborn, which causes stress. Excessive stress, the report warns, can halt labor and impact the newborn's brain development, and is implicated in a slew of prenatal complications.

Women have sometimes been criticized for focusing too much on the “birth experience.” The report suggests that, for our health and safety, and that of our babies, the experience is exactly where our focus should lie.