"About 40 per cent of women who give birth prematurely are primarily what we call the idiopathic pre-term births where we don't understand why they went into labour early," says Dr. John Challis, professor of medicine and physiology at the University of Toronto, and one of the senior authors of a paper in the April 25 issue of Science. "Our research with sheep in this paper suggests that a proportion of those idiopathic pre-term births could be associated with maternal undernutrition before the start of pregnancy."

In normal pregnancy, the fetus triggers the onset of its own birth, explains Dr. Frank Bloomfield, lead author of the paper and now a senior lecturer at the University of Auckland. In animals, it is well known that the fetus does this through activation of its adrenal gland to produce a surge of cortisol in the blood. The surge of cortisol is the catalyst for the chain of events that eventually lead to its birth. It is believed that human labour follows the same type of process.

The problem is when birth occurs prematurely, adds Challis, who is also scientific director of the Institute of Human Development, Child and Youth Health of the Canadian Institutes of Health Research. "Those born prematurely have less opportunity for their lungs and organs to develop in utero in preparation for life outside the womb. The nature of these experiments prevented us from exploring the longer term viability of the premature lambs. But we believe that the cortisol from the adrenal gland of the offspring, which provides the stimulus to the birthing process, also assists in maturing organ systems like the lungs, which the baby needs to breathe air once it's been born. If there has not been enough cortisol to c
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Contact: Janet Wong
jf.wong@utoronto.ca
416-978-5949
University of Toronto
24-Apr-2003