It8217;s Good to be on time

Australian researchers have found that a pregnancy's duration is determined at conception. A biological alarm clock is set ticking; when ...

Australian researchers have found that a pregnancy8217;s duration is determined at conception. A biological alarm clock is set ticking; when it 8220;rings8221; labour begins. This idea runs counter to current theories which stress that pregnancies will last for around 40 weeks unless problems 8212; most of them unpredictable develop. One in 15 babies is born prematurely, and many suffer lung damage, cerebral palsy, paralysis, deafness, blindness and other health problems. Cutting premature births would reduce suffering and slash health service costs. 8220;This work is extremely important,8221; said Professor Ashley Grossman of Bart8217;s hospital, London. 8220;It is based on carefully controlled experiments and beautifully designed studies. It has not yet been replicated by other scientists, but I am confident that it soon will be.8221;

The work by Professor Roger Smith and Dr Mark McLean of Newcastle University, New South Wales is highlighted in the latest issue of Scientific American magazine. 8220;I was interested in premature births because they have remained a serious medical problem for the past 30 years,8221; Smith told The Observer.

8220;We have conquered other problems in obstetrics, but not this one. We put a man on the Moon three decades ago, but we still don8217;t understand how we are born.8221;

This ignorance may soon disappear, however. Smith and his colleagues have found that corticotropin-releasing hormone CRH plays a crucial role in triggering labour.

As gestation progresses, CRH levels build up until they trigger a biochemical cascade that causes womb muscles to harden and contract, and the cervix to loosen and widen. Birth then ensues.

Research by Smith and McLean on 500 pregnant women has revealed that CRH levels correlated with length of pregnancy. Those with high levels at the beginning of pregnancy were most likely to deliver prematurely, and those with low levels were most likely to give birth late.

8220;In other words, we found a clock that is set early in pregnancy and controls the speed at which that pregnancy proceeds,8221; said Smith.

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Dr Dimitri Grammatopoulis of Warwick University said: 8220;CRH levels give us a way of predicting how long a woman8217;s pregnancy will last. It is a critically important handle on the whole problem of premature birth.8221;

He pointed out that CRH influences the production of a number of other important chemicals such as estrogen and prostaglandin that are also involved in triggering labour.

8220;If we can spot a woman in danger of giving birth after only 28 weeks8217; pregnancy, we can at least ensure that she is moved to a hospital and that she is constantly monitored,8221; said Smith.

8220;At present, we can only give drugs that will delay birth by a few hours, or days at the most. However, these will at least help to reduce some of the worst effects of premature birth, particularly lung damage.8221;

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By uncovering the cascade of chemicals that are triggered by rising CRH levels, scientists have also been provided with a route to developing drugs that might block the onset of labour.

Several groups around the world are now working on different approaches Some are testing chemicals that block the action of prostaglandin, others that counter the effects of oxytocin, another labour-inducing substance triggered by CRH.

8220;Both a test for CRH, and drugs to halt premature births, are still undergoing trials 8212; some in humans and some in animals,8221; said Smith. 8220;We won8217;t have either for another four or five years, but when they arrive they will have a great impact, I8217;m sure of that.8221;