Tracking Disease Back to the Womb
Birth of Good Health
By L.A. McKeown
June 11, 2001 -- By now, most of us are used to hearing that what we eat, how much we exercise, how we deal with stress, and what's in our genes go a long way toward influencing our risk of diabetes, heart disease, or other health problems. But now some scientists are suggesting that our risks may have been in place before we even saw the light of day.
These scientists are looking closer than ever before at the fascinating world of 'womb life' and finding that what happens there during the time from conception to birth lays the foundation for the overall health of an individual from infancy to adulthood.
"This is the biggest story in human health and we need to wake up," says Peter Nathanielsz, MD, PhD, a pioneer of this fairly new branch of research. Conditions in the womb are so important, he says, they can determine whether you develop high blood pressure, stroke, obesity, or diabetes when you're much older.
In his book, Life in the Womb: the Origin of Health and Disease, Nathanielsz, a professor of reproductive medicine at Cornell University in Ithaca, N.Y., describes the unborn baby as a "body machine" that must be well-constructed and well-prepared during all phases of development.
Although the theory could cause some women to feel additional pressure to have a perfect pregnancy, Nathanielsz says it's important to keep in mind that how a child lives once he or she is born -- the "maintenance" we do on our "body machine" -- still has a significant impact on overall health.
The greatest concern during pregnancy is that the conditions in the womb, if they are unfavorable, can essentially stack the deck against our health.
But unlike birth defects, which may be caused by a mother who smokes, drinks, uses drugs, or is exposed to harmful chemicals, the kinds of problems that occur in the womb that can have a lifetime impact on health may be more subtle decisions on the part of a mother -- such as not eating properly.
A developing fetus experiencing nutritional deprivation or other unhealthy conditions in the womb will divert a significant amount of its resources to its developing brain at the expense of other organs, Nathanielsz says. This leaves important organs like the kidney, heart, and blood vessels vulnerable to not developing properly and possibly increases the risk for diseases related to those organs as the individual ages.
The research being done now should give women and their doctors a better understanding of things that previously were not known about the biology of pregnancy and the vulnerability of the fetus at certain crucial times during development.
"We pass more biological milestones before we are born than afterward," Nathanielsz says. "We go from one cell to billions of cells. Is it therefore surprising that how those changes happen is going to have a lifetime effect on us?"
Diabetes and Heart Disease
The risk of getting diabetes is significantly increased if your mother has diabetes, studies show, because changes in the mother's blood sugar levels and insulin status appear to affect her baby's insulin status. In this situation, as in so many during fetal development, the fetus is held captive to the mother's actions, according to Nathanielsz. Taking proper care of your diabetes and taking steps to avoid developing diabetes in pregnancy -- like following a healthy diet, exercising regularly, and not gaining too much weight -- are important for diabetic mothers and those with risk factors for diabetes to keep in mind.
In the last few years, research also has linked being born small with increased risk of diabetes. In one study, girls born weighing less than 5 pounds due to improper growth in the womb had almost double the risk of developing diabetes as girls born weighing 7 to 8.5 pounds.
A similar study of over 70,000 women found that those born weighing less than 5.5 pounds had a 23% higher risk of heart disease than women with higher birth weights.
According to researcher David J.P. Barker, these low birth weights can be the result of the mother not eating properly or something happening to her that interferes with the nutrition that gets to her fetus.
Barker, who is director of the environmental epidemiology unit at the University of Southampton in England, studied men with heart disease, going back to their birth records to check their weights. He found that a significant percentage of them were born small.
One of the problems seems to be that when children are born small, doctors and parents encourage weight gain at a young age. But Barker says it appears the internal mechanisms that govern the child's weight and height may be set in the womb. Therefore, an underweight or underdeveloped baby who begins to gain weight rapidly to become "normal" weight undergoes changes in levels of various hormones, and those early changes may be the starting point for a chain-reaction of problems that occur later in life.
Another possibility is that the kidneys may not develop properly in smaller babies. If this happens, your kidneys may never be able to regulate your blood pressure as adequately as they should, which could lead to high blood pressure, a leading cause of heart disease.
Estrogen: The Great Communicator
One fascinating thing scientists have learned from this new line of research is an understanding that during pregnancy there exists a complicated internal relationship involving hormones and signaling mechanisms that help the mother's body communicate with that of her fetus. This communication, though not on any conscious level, is believed to be crucial to the healthy and proper development of the child.
During pregnancy a woman's level of the hormone estrogen rises. Some have now tapped estrogen as the head of the invisible army that moves this complex internal information back and forth from the mother to her fetus.
Researcher Gerald J. Pepe, PhD, and colleague Eugene Albrecht, PhD, have spent years studying the effects of estrogen during pregnancy. Pepe says estrogen plays a major role in the development of the fetus' adrenal glands -- located above the kidney -- which produce hormones including the stress hormone cortisol. Cortisol is crucial to the maturation of the lungs, liver, and other important organs and tissues.
During pregnancy, cortisol passes through the placenta from mother to fetus because the fetus itself does not start producing cortisol until about two-thirds of the way through pregnancy. At a given point, the mother's estrogen level signals to the fetus to start producing its own cortisol, which jumpstarts the development of other fetal systems and organs. If the signal doesn't get through, the fetus doesn't develop properly and may die.
"So the estrogen indirectly, by regulating cortisol metabolism, is controlling fetal maturation," says Pepe, of Eastern Virginia Medical School, in Norfolk.
This research is still in the preliminary stages and doctors don't yet test pregnant women's estrogen levels, but it may be a reality some day.
What Can Be Done:
Programming Your Health Risks
There is a growing support for the idea that your metabolism and other bodily mechanisms are "set" or programmed early in life. Some experts think the best weapon against these pre-programmed risks is breastfeeding because components in breast milk help boost the immune system, protect against infection, and provide essential nutrition that growing babies need.
And there may be other long-term benefits as well, says Robert E. Lyle, MD.
"There are some fairly recent large-scale studies in Germany suggesting that breastfeeding protects against obesity, and of course, obesity is related to heart disease and cancer and diabetes," says Lyle, associate professor of pediatrics and neonatology at Arkansas Children's Hospital, in Little Rock.
More recent support comes from a study in The Journal of the American Medical Association. American researchers found that infants whose mothers gave them more breast milk than formula or whose mothers breastfed them for 6 months or longer had the lowest risk of being overweight by the time they were 9-14 years of age.
"Our study is one more fact to put in the 'pro' column for breastfeeding," says the study's lead author, Matthew Gillman, MD, of Harvard University School of Medicine in Boston. "But if the water's already under the bridge -- if the woman has not breastfed -- there are plenty of other determinants of weight gain in childhood. This is not the only factor."
Likewise, Nathanielsz says while women should do all they can during pregnancy and after their child is born to ensure optimum health, he is concerned that women will be made by their doctors or by society to feel guilty if their children grow up to have diseases that could have been avoided by making different decisions or by correcting subtle missteps during pregnancy.
Rather than blame the individual mothers, he says, the answer to healthier pregnancies and healthier babies is removing barriers that stand in the way of optimal prenatal care for all women.
Tips For Healthy Eating During Pregnancy:
Since research suggests inadequate nutrition could be a main factor in causing unfavorable conditions in the womb, here are some guidelines for eating healthy when you're expecting:
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