Even modest restrictions in maternal nutrition around the time of conception can lead to premature births and long-term adverse health effects for offspring, suggests new research carried out on sheep.
Scientists from Canada, New Zealand and Australia, studied the effects of restricted nutrition on ewes, half of which were underfed for a short time before and following conception. This reduced their body weights by 15 per cent. Even after nutrition was returned to normal, foetuses of undernourished ewes had accelerated maturation of their adrenal glands, prompting their premature delivery by about one week, on average, found researchers.
Dr John Challis, professor of medicine and physiology at the University of Toronto, Canada, said the study suggests that a proportion of idiopathic (unknown cause) pre-term births could be associated with maternal undernutrition before the start of pregnancy.
In normal pregnancy, the foetus triggers the onset of its own birth, explained Dr Frank Bloomfield, a senior lecturer at the University of Auckland. In animals, it is well known that the foetus 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, added Challis. "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. If there has not been enough cortisol to cause lung maturation in utero, then the offspring develops respiratory distress and may succumb and die outside the womb," he said.
Using about 40 sheep, Challis, Bloomfield and colleagues from New Zealand and Australia divided ewes into two groups. The control group of 20 ewes was fully nourished prior to mating and during the entire gestational period.
In the experimental group, ewes were underfed and maternal body weights were reduced by approximately 15 per cent (about 15 pounds) 60 days prior to mating and for an additional 30 days after conception. Fifteen per cent is considered a mild to moderate nutrient restriction for sheep, said Bloomfield. After that time, nourishment levels were increased and ewes were allowed to eat as much as they desired.
While the normal gestational period for sheep is about 145 to 150 days, the foetuses of undernourished ewes were on average delivered one week earlier than control. In some cases, the ewes delivered as much as 15 to 20 days early.
Pre-term birth is a problem throughout the world, but Challis and Bloomfield note that the incidence of pre-term birth in affluent Western societies has increased over the past decade and remains the number one cause of perinatal illness and death. Challis suggests the problem may have to do with women who diet prior to pregnancy, fearing they will be unable to shed the excess weight afterwards.
"Women need to think about proper diet and food intake before they even know they're pregnant because proper nutrition after pregnancy may not compensate for the lack of it beforehand. Even a modest restriction around the time of conception could have far-reaching consequences," said Challis. "We know now that this period of undernutrition could impact on the development of the pituitary and adrenal glands of the baby and may well affect the development of other organ systems."
Bloomfield also pointed to data from the UK suggesting that up to 40 per cent of women of child-bearing age do not eat a good, well-balanced diet and that this may be a strong factor in premature delivery.
Full details of the study can be found in the journal Science.