Fresh Science

Stress before birth leads to hypertension in adulthood. Trial in sheep suggest that high blood pressure ( suffered by 25% of all adults over 45 years of age) may have been programmed by events which occurred before the individual was born.

An unborn child’s exposure to ‘stress hormones’ in the very early stages of the mother’s pregnancy may lead on to high blood pressure as an adult, according to new research by Melbourne scientists.

The research at the Howard Florey Institute, an affiliated institution of the University of Melbourne, is described in a paper published in the internationally recognised journal Clinical Science.

Early warning of potential high blood pressure in susceptible people could provide a vital and timely opportunity for effective lifestyle education. At least 25% of men and women over 45 years develop high blood pressure, a major risk factor for stroke, and heart disease.

The new findings come from work by Dr Miodrag Dodic, in PhD studies at the Howard Florey under the supervision of Professor John Coghlan and Dr Marelyn Wintour, and in collaboration with Dr Clive May.

Dr Dodic gave high doses of the synthetic ‘stress hormone’ dexamethasone to pregnant ewes during two days early in pregnancy. The lambs they were carrying developed high blood pressure as adults. However, ewes treated closer to mid-pregnancy, with the same amount of ‘stress hormone’, did not develop hypertension in later life.

Dr Dodic says studies in the UK in the 1980s showed low birth weight babies have a four to five-fold risk of developing hypertension as adults.

“The low birth weight was attributed to poor nutrition of the mother during pregnancy. More recently a link was found between undernourishment of the mother and excessive exposure of the developing fetus to ‘stress hormones’ from the adrenal gland. Poor nutrition of the mother is perceived by the hormonal system as ‘stress’.

“The remarkable aspect of these finding is that it is not only the low birth-weight babies who are potentially at risk of developing high blood pressure as adults”, he says.

Dr Dodic and his colleagues produced the high stress hormone levels so early in pregnancy, and for such a short time, that the lambs were of normal birth-weight, about 4 kgs.

The implications are that the baby whose mother experiences a short traumatic experience, probably during the first three months of pregnancy, may have been ‘programmed’ to have high blood pressure as an adult.

“Exactly how this early ‘stress hormone’ exposure leads to the development of high blood pressure in adult life is unknown but some fascinating clues are coming out of our ongoing research”, says Dr Dodic.