From the moment an embryo attaches itself to the wall of a womb, a human being’s blueprint for life begins to unfold–but not simply in the way many people might think.
Dr. Peter Nathanielsz, a biomedical researcher who has spent his career trying to unravel the mysteries of fetal life, said, “I don’t think anything is more fatalistic than believing we are just a product of our genes.”
Nathanielsz, director of the laboratory for pregnancy and newborn research at Cornell University, said he believes that the womb environment is just as important as genes and, potentially, more controllable.
Research is accumulating, he said, indicating that if conditions during gestation are not optimal, a child’s lifetime physical and mental health can be programmed to include susceptibility to heart disease, obesity, high blood pressure, diabetes, poor emotional resilience and resistance to infection.
The burgeoning field of “prenatal programming,” Nathanielsz said, shows that “how and when we leave this world is shaped in large part by how we entered it.
“The really critical points are in the first 7 to 10 weeks as the placenta is beginning to be laid down,” said Nathanielsz, author of “The Prenatal Prescription” (HarperCollins, $25).
The placenta, often called afterbirth, demands more respect, according to Nathanielsz, because it plays a key role in fetal programming.
Simply put, the placenta is a supply line, enabling the baby to get oxygen and nourishment and flushing out waste products.
“It produces almost every hormone we know,” Nathanielsz said.
And the size of the placenta at birth may provide the first clue about the fetal environment.
British physician-scientist Dr. David Barker, one of the pioneers in the field, discovered that babies with a large placenta were more likely to have high blood pressure later in life. He found that the clever fetus grows a larger placenta to compensate for suboptimal womb conditions.
This breakthrough came when meticulous birth records from the 1900s that recorded the weight of the placenta were discovered in England and then matched with patients’ adult medical histories.
Barker also found that fetal growth in the womb is directly related to how well people in old age control the level of glucose in their blood. Glucose levels that are too high or too low can affect any number of disease processes.
Barker’s work, begun in the late 1960s, initially was considered controversial and was resisted by the medical establishment. But attitudes about fetal programming are changing.
“In the last two years I have been to about five meetings on this subject at the National Institutes of Health,” Nathanielsz said. “That shows you how much it is accepted, although there’s still a lot of work to be done, like everything.”
Nathanielsz recently was awarded a grant from the National Institute on Aging to study placentas.
The idea that good nutrition is important before and during pregnancy is sure to draw more attention. Nathanielsz said its importance was underscored by data from the so-called Dutch hunger winter during the closing days of World War II.
Dr. Clement Smith, a Harvard pediatrician, found that the precise time in pregnancy when bad nutrition occurred was important in how the Dutch babies, now in their late 50s, fared.
Not surprisingly, the babies who were the most adversely affected were those who lived through the entire period of food deprivation while in the womb. They were the smallest, had the most health problems and mortality levels 10 times higher than normal.
Those subject to starvation in the first half of their mothers’ pregnancies were more likely to be obese than those born a few months into the famine and deprived only during the last trimester of the pregnancy.
“We know they have a higher incidence of obesity and diabetes,” Nathanielsz said, adding that further animal research should “nail down” the findings.
Meanwhile, evidence from laboratory experiments is accumulating.
For example, when British researchers undernourished pregnant laboratory rats for the first four days of pregnancy, a large proportion of their 21-day pregnancy, the result was a placenta that wasn’t really formed. “The rats then later have high blood pressure,” Nathanielsz said.
Pregnant mothers who eat poorly program their children’s bodies to expect shortages of food after they are born, and thus the children are better at hoarding calories.
Babies who learn these “tricks of metabolism” in the womb are more likely to be overweight or obese when they grow up. Their tendency is sometimes referred to as “thrifty metabolism.”
Nathanielsz stressed that data on prenatal programming should not add to the worries of pregnant women or promote feelings of guilt.
“Pregnancy is normally normal,” he said. “We know that there is no such thing as a perfect baby. So the clarion call is to do the best we can in terms of nutrition, exercise, [managing] stress.
“Clearly, the biology shows that women’s health is far more important than men’s health to us as a society, as a species. All these experiments, studies with animals show how women’s health is passed from one generation to the next, from mother to daughter to daughter to daughter. . . . “
“In other words,” Nathanielsz writes, “if your child is a girl, her own womb and other reproductive organs will feel the effects of the environment you provided for her in your womb.
“If she is presented with challenges to her growth, her body may be smaller than it should be, she may have difficulty keeping her blood sugar in balance, her kidneys may not function correctly, her response to stress may be higher. When she grows up and becomes pregnant herself, these factors may affect the quality of the womb environment that she is able to provide for her child.”
Nathanielsz added that this doesn’t “deny the existence of genes. Nobody is saying cells aren’t instructed by genes.”
But he calls fetal programming a “major societal issue.
“We’re not going to be able to change the gene pool overnight, but we can do a tremendous amount to improve long-term health. Why do we spend millions cobbling up arteries at age 60 and not spend the money preventing the problem earlier?”
