There was a time when the womb was regarded as a pristine environment for a ‘fetonaut’ to travel safely for 9 months until birth, protected by a shield-like placenta. No longer. The effects of smoking, thalidomide and binge drinking show it is all too vulnerable to external threats.
This realization was extended by David Barker, an epidemiologist whom I met but only once at a Swiss symposium on evolution and health. He was head of a research unit at the University of Southampton and then winning over detractors to his belief that prenatal malnutrition has delayed impacts until midlife or even later.
From searching British medical records, he found low birth weight predicted heart disease, stroke and high blood pressure in adult life, some of the most common medical blights. His critics dismissed the connection as mere correlation—not causation— but as years rolled by there was confirmation from other sources and connections with obesity and diabetes type 2.
At first called the Barker hypothesis, it is now known as the fetal origins of adult disease and as spurred research into late effects beyond those he studied.
Adverse health effects were also found among Dutch people born to mothers subsisting on a forced daily diet of under 1,000 calories in the last year of World War II. More harms were reported in children conceived around the time of the Chernobyl nuclear disaster and a famine during Chairman Mao’s ‘Great Leap Forward’. They imply that health and vitality are molded by our environment as well as genes at tender stages that go unseen.
A gravid womb is not like an unmanned space capsule controlled from afar and tossed by storms of plasma from the solar corona. Like an astronaut, a fetus can make adjustments to adapt to changing conditions and improve its safety. This so-called developmental plasticity evolved to increase the chances of survival in times of food shortage. Sometimes called a thrifty phenotype, the baby who emerges is adapted to thrive in the meager circumstances he or she is born to. But if a mismatch exists between prenatal poverty and postnatal affluence the resulting catch-up growth, although apparently welcome, may come at a price if adaptations made in the womb are no longer appropriate.
Adaptations to low oxygen and stress hormones can also play a role, either independently or with malnutrition, and the effects on cell biology and physiology are multifarious and complex. The root of the problem is likely epigenetics in which genes are switched on or off in different cells and states but the sequence of letters in the DNA code are unaltered. Rather insidiously, some epigenetic changes can be inherited by the children and even grandchildren of those originally affected.
So, what has that got to do with the COVID-19 pandemic? Major economic interruptions, like the Great Recession from 2007 that lasted a decade, are known to cause persistent mental and physical health problems, especially among racial and ethnic minorities. But what about acute pandemics that last only months?
Douglas Almond, a health economist at Columbia University, studied people conceived in 1918 and 1919. They suffered far more disadvantages in life if conceived during the flu pandemic than a few months earlier or later, even after adjusting for social class, etc. He reported, “(they) attained lower educational achievement, income, and socioeconomic status … 15% less likely to graduate high school, 15% more likely to be poor, and 20% more likely to be disabled as adults.”
There will be a huge sigh of relief, of course, when COVID-19 is conquered by vaccines, but that won’t be the end of the story. There are likely to be long-term negative consequences for the generation of innocents currently in utero.
This shouldn’t unduly alarm women currently pregnant because the projection is demographic, and the great majority of babies will be fine. The cohort conceived in the flu pandemic a century ago produced as many outstanding people as other generations, men and women like Richard Feynman, Katherine Johnson, Nelson Mandela and Edmund Hillary. Some of them were doubtlessly born in acutely affected communities. But the fetal origins hypothesis urges more research on the unborn to mitigate the chronic personal and societal health impacts of infection.
