Mother blame 2014: epigenetics edition

Blame

It’s seems its always the mother’s fault.

There is a long and storied history of mother blame extending back millennia. Women who couldn’t conceive were labeled “barren” even though infertility is caused by male factors 20% of the time. Women who had only daughters and no sons were blamed for the sex of their children, even though it is sperm that determine gender, not ova. For hundreds of years of recent history, women were told that their dreams could affect the outcome of pregnancy; dream of something frightening and the baby might be deformed. Within the past century, “refrigerator mothers” were blamed for autism even though there was never any evidence to support such a link.

Mother blame received impetus with the discovery of teratogens, chemical compounds (natural and synthesized) that do actually result in birth defects in offspring. Visions of teratogens (“toxins”) dance in the heads of many who care for pregnant women even though actual teratogens are rare. There is no question that alcohol (ethanol) is a teratogen in large amounts, but there’s nothing to justify the widespread hysteria over small amounts that is prevalent today.

The latest recruit to the deeply satisfying pastime of mother blame is epigenetics; all the scourges of old age in wealthy countries, like diabetes, obesity and cardiac disease, can be blamed on mothers changing the epigenetics of their offspring. No group has embraced this tactic with greater relish than natural childbirth advocates. The current favorite meme in the natural childbirth community is the claim that Cesarean sections cause epigenetic changes harmful to babies.

It’s not surprising that natural childbirth advocates seized on epigenetics with such enthusiasm. It is startlingly clear to anyone who bothers to look that modern obstetrics saves countless lives of mothers and babies each and every year. It’s pretty hard to oppose lifesaving interventions. But wait! What if those interventions caused health problems down the line? Then C-sections could be deemed harmful even if they saved lives.

Never mind that there’s absolutely no evidence than any maternal behaviors cause epigenetic changes. Mother blaming is too much fun to stop.

I’m not the only one who has noticed this.

In a recent edition of the journal Nature, seven scholars of history, philosophy, gender studies and population health offered a commentary entitled Society: Don’t blame the mothers. The authors identify the problem:

There is a long history of society blaming mothers for the ill health of their children… First recognized in the 1970s, fetal alcohol syndrome (FAS) is a collection of physical and mental problems in children of women who drink heavily during pregnancy. In 1981, the US Surgeon General advised that no level of alcohol consumption was safe for pregnant women. Drinking during pregnancy was stigmatized and even criminalized. Bars and restaurants were required to display warnings that drinking causes birth defects. Many moderate drinkers stopped consuming alcohol during pregnancy, but rates of FAS did not fall…

Until the nineteenth century, medical texts attributed birth deformities, mental defects and criminal tendencies to the mother’s diet and nerves, and to the company she kept during pregnancy.

Although it does not yet go to the same extremes, public reaction to developmental origins of health and disease (DOHaD) research today resembles that of the past in disturbing ways. A mother’s individual influence over a vulnerable fetus is emphasized; the role of societal factors is not. And studies now extend beyond substance use, to include all aspects of daily life.

The authors note that the scientific evidence to support mother blame by epigenetics is preliminary, weak, conflicting and inconclusive.

The authors offer four caveats when considering research on epigenetics:

First, avoid extrapolating from animal studies to humans without qualification. The short lifespans and large litter sizes favoured for lab studies often make animal models poor proxies for human reproduction. Second, emphasize the role of both paternal and maternal effects. This can counterbalance the tendency to pin poor outcomes on maternal behaviour. Third, convey complexity. Intrauterine exposures can raise or lower disease risk, but so too can a plethora of other intertwined genetic, lifestyle, socio-economic and environmental factors that are poorly understood. Fourth, recognize the role of society. Many of the intrauterine stressors that DOHaD identifies as having adverse intergenerational effects correlate with social gradients of class, race and gender. This points to the need for societal changes rather than individual solutions. (my emphasis)

I’d like to offer a fifth caveat: Consider whether it even makes sense to implicate epigenetics.

Take the natural childbirth love affair with the epigenetic “risks” of C-sections. It reflects a fundamental misunderstanding of what epigenetics is and how it works.

Trans-generational epigenetic changes are heritable changes in the regulation of gene expression. The classic example is famine that leads to epigenetic changes that render individuals better able to survive during food scarcity. That improved ability can be passed on to children and grandchildren. The epigenetic changes can become harmful if the environment changes radically. The epigenetic change that allowed a grandfather to survive a famine might increase the risk of a daughter being obese.

That’s the way that epigenetic changes purportedly cause harm, although there is a serious problem with that argument. If epigenetic changes occur so easily, shouldn’t the granddaughter experience epigenetic changes that decreased the risk of obesity?

The bottom line is clear. At the moment, there is no reliable, reproducible scientific evidence that C-sections cause epigenetic changes. There’s no reason to think that C-sections would cause harmful epigenetic changes. There’s no reason to think that trans-generational epigenetic changes that caused harm to future generations wouldn’t change back.

While it is certainly possible for mothers to cause harm to unborn children (think thalidomide or excess Vitamin A ingestion), there is no evidence that  C-sections cause harm or that epigenetics has anything to do with it.