scott-forbes
UWinnipeg evolutionary biologist publishes major new research paper
WINNIPEG, MB – Getting sick while pregnant is a sign that the embryo is healthy and mother is iodine sufficient, according to University of Winnipeg Professor Dr. Scott Forbes (Biology), whose research paper was just published in Evolution and Human Behavior.
Globally iodine deficiency during pregnancy is the most important correctable source of cognitive impairment in humans. Pregnancy sickness arises as from tug of war between mother who needs to hold on to her scarce iodine, and embryos who need that iodine for brain development. Embryos use a hormonal manipulation to hijack their mother’s thyroid system to release vital iodine said Forbes, and “pregnancy sickness is a byproduct of this process.” Mother and embryo have differing interests, he adds.
Forbes, an evolutionary biologist, began researching this topic in the mid 1990’s and most recently has been data mining — scouring biological literature to author Embryo quality: the missing link between pregnancy sickness and pregnancy outcome.
Women who do not get sick are much more likely to experience pregnancy loss, largely because embryos bear chromosomal defects. They cannot produce sufficient levels of the hormone manipulating mother’s thyroid system. But even normal embryos cannot generate pregnancy sickness if their mothers are iodine deficient. Iodine, an essential micronutrient in the maternal diet, is key, explains Forbes. Too little is harmful to the embryo, but so too is too much. In iodine rich environments, higher levels of pregnancy sickness are beneficial, as it reduces the intake of iodine rich foods. In Korea and Japan, for example, women eat very rich iodine diets including seafood and kelp, and exhibit the highest rates of pregnancy sickness in the world. In iodine poor environments, the incidence of pregnancy sickness is much lower.
The work has implications for clinical medicine. Whether there should be routine thyroid testing for pregnant women is controversial. An absence of pregnancy sickness, particularly in women under age 35, is an indicator for thyroid testing. Maternal iodine deficiency is harmful to the embryo, but is easily correctable. In older women, an absence of pregnancy sickness is more likely to reflect an embryo with chromosomal defects.
Dr. Forbes is available to do one-on-one for media interviews. S.forbes@uwinnipeg.ca or 204-786-9441
BACKGROUND ABSTRACT
Pregnancy sickness is an enduring enigma – though it occurs in most women across the globe during the first trimester of pregnancy, why is unclear. Epidemiologists have long known that a higher level of pregnancy sickness is correlated with a positive pregnancy outcome. Early pregnancy loss is much less likely in women who experience pregnancy nausea or vomiting compared to those who do not. Some have suggested that pregnancy sickness protects the developing embryo from dietary toxins or pathogens, explaining the link between pregnancy sickness and pregnancy outcome. However, recent work shows that the link is stronger in women over age 35, when chromosomal defects become more common; and we now know that most spontaneous abortions can be forecast before the onset of pregnancy sickness. Thus unless the fundamental laws of space and time have been changed, the link between pregnancy sickness and pregnancy outcome is not causal. Rather, pregnancy sickness serves as an index of high quality offspring unlikely to be spontaneously aborted, and operates through the thyroid axis. High levels of pregnancy sickness are associated with a hyperthyroidism; an absence of pregnancy sickness is associated with hypothyroidism. Dietary changes associated with pregnancy sickness calibrate the dietary intake of iodine that is essential for thyroid function and brain development of the embryo. Iodine-rich foods (seafoods, dairy, meat) are the chief targets of food aversions associated with pregnancy sickness. Too little iodine impairs brain development, thus in iodine poor environments, pregnancy sickness that decreases iodine intake is maladaptive. Excessive iodine also harms embryo development, and in iodine rich environments, pregnancy sickness is beneficial as it reduces iodine intake.
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MEDIA CONTACT
Diane Poulin, Senior Communications Specialist, The University of Winnipeg
P: 204.988.7135, E: d.poulin@uwinnipeg.ca
