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You leave the womb sterile, or so it is generally thought, but are liberally swabbed with your mother’s personal complement of microbes as you move through the birth canal. We are only beginning to understand the importance and nature of a woman’s vaginal microbiome. Babies born by Cesarean section are robbed of this initial wash. The consequences for the baby can be profound. Various studies have found that people born by C-section have substantially increased risks for type 1 diabetes, asthma, celiac disease, and even obesity and an eightfold greater risk of developing allergies. Cesarean babies eventually acquire the same mix of microbes as those born vaginally—by a year their microbiota are usually indistinguishable—but there is something about those initial exposures that makes a long-term difference. No one has figured out quite why that should be.
Doctors and their hospitals can charge more for Cesarean births than for vaginal ones, and women understandably often like to know exactly when birth will take place. One-third of women in the United States give birth by Cesarean section now, and more than 60 percent of Cesareans are done for convenience rather than from medical necessity. In Brazil, nearly 60 percent of all births are by C-section; in Britain, it is 23 percent; in the Netherlands, it is 13 percent. If it were done only for medical reasons, the rate would be between 5 and 10 percent.
Other useful microbes are picked up from the mother’s skin. Martin Blaser, a doctor and professor at New York University, suggests that the rush to clean up babies as soon as they are born may actually be depriving them of protective microorganisms.
On top of all that, about four women in every ten are given antibiotics during delivery, which means that doctors are declaring war on babies’ microbes just as they are acquiring them. We’ve no idea what consequences this has for their long-term health, but it’s unlikely to be good. There are concerns already that certain beneficial bacteria are becoming endangered. B. infantis, an important microbe in mother’s milk, is found in up to 90 percent of children in developing countries but as little as 30 percent in the developed world.
Whether born by Cesarean or not, by the age of one the average baby has accumulated about a hundred trillion microbes, or so it has been estimated. But by that time, for reasons unknown, it appears to be too late to reverse the predisposition for acquiring certain diseases.
One of the most extraordinary features of early life is that nursing mothers produce over two hundred kinds of complex sugars—the formal name is oligosaccharides—in their milk that their babies cannot digest because humans lack the necessary enzymes. The oligosaccharides are produced purely for the benefit of the baby’s gut microbes—as bribes, in effect. As well as nurturing symbiotic bacteria, breast milk is full of antibodies. There is some evidence that a nursing mother absorbs a little of her suckling baby’s saliva through her breast ducts and that this is analyzed by her immune system, which adjusts the amount and types of antibodies she supplies to the baby, according to its needs. Isn’t life marvelous?
In 1962, only 20 percent of American women breast-fed their babies. By 1977, this had increased to 40 percent, still clearly a minority. Today almost 80 percent of American women breast-feed just after birth, though that number falls to 49 percent after six months and 27 percent after a year. In Britain, the proportion starts at 81 percent but then plunges to 34 percent after six months and just 0.5 percent after a year, the worst rate in the developed world. In the poorer nations, many women were long encouraged by advertising to believe that infant formula was better for their babies than their own milk and so began switching to formula. But formula was expensive, so often they watered it down to make it go further. Sometimes also the only water available to them was less clean than their own breast milk. The result in some places was an increase in childhood mortality.
Although formulas have greatly improved over the years, no formula can fully replicate the immunological benefits of mother’s milk. In the summer of 2018, the administration of President Donald Trump provoked dismay among many health authorities by opposing an international resolution to encourage breast-feeding and reportedly threatened Ecuador, the sponsor of the initiative, with trade sanctions if it didn’t change its position. Cynics pointed out that the infant formula industry, which is worth $70 billion a year, might have had a hand in determining the U.S. position. A Department of Health and Human Services spokesperson denied that that was the case and said that America was merely “fighting to protect women’s abilities to make the best choices for the nutrition of their babies” and to make sure that they were not denied access to formula—something the resolution wouldn’t have done anyway.
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In 1986, Professor David Barker of the University of Southampton in England proposed what has become known as the Barker hypothesis or, a little less snappily, the theory of fetal origins of adult disease. Barker, an epidemiologist, posited that what happens in the womb can determine health and well-being for the rest of one’s life. “For every organ, there is a critical period, often very brief, when it goes through development,” he said not long before his death in 2013. “It happens for different organs at different times. After birth only the liver and the brain and the immune system remain plastic. Everything else is done.”
Most authorities now extend that period of crucial vulnerability from the moment of your conception to your second birthday—what has become known as the first thousand days. That means that what happens to you in this comparatively brief, formative period of your life can powerfully influence how comfortably alive you are decades later.
A famous example of this tendency was revealed by studies done in the Netherlands of people who lived through a very serious famine in the winter of 1944, when Nazi Germany stopped food from entering the parts of the country that were still in its control. The babies conceived during the famine had miraculously normal birth weights, presumably because their mothers instinctively diverted nutrition to their developing fetuses. And because the famine ended with the fall of Germany the following year, the children grew up eating as healthily and as well as any other children in the world. To the delight of all concerned, they seemed to escape all the effects of the Great Hunger, as it was known, and were indistinguishable from children born elsewhere in less stressful circumstances. But then a disturbing thing happened. As they reached their fifties and sixties, the famine children developed double the rate of heart disease, and increased rates of cancer, diabetes, and other life-compromising maladies, as children born elsewhere at the same time.
These days the legacy newborn babies bring into the world with them isn’t a lack of nutrition but the opposite. So they are not only being born into households where people eat more and exercise less, but have an innate and enhanced vulnerability to succumb to the diseases that poor lifestyles bring.
It has been suggested that children growing up today will be the first in modern history to live shorter, less healthy lives than those of their parents. We aren’t just eating ourselves into early graves, it seems, but breeding children to jump in alongside us.