STAYING calm during the first trimester of pregnancy could be the key to reducing the chances of having a stressed-out baby.

A world-first Griffith University study has set out to prove the theory.

Studies of animals have shown a link between stress in the first three months of gestation and unhappy bubs.

But Associate Professor Melanie Zimmer-Gembeck said hers would be the first study in which pregnant women were tested from as early as 12 weeks to nearly a year post birth.

The babies would undergo the same observations as their mothers and their saliva would be tested for levels of the stress hormone cortisol.

Prof Zimmer-Gembeck said the first three months of pregnancy could prove to be the most important because the fetus depended more heavily on the mother and shared her cortisol.

But the director of Griffith's Family Interaction Research Program said she also hoped to prove that parents could still compensate following the birth by the way they approached parenting.

Prof Zimmer-Gembeck needs about 50 pregnant women for the study.

Tugun mum Sarah Simpson, who recently gave birth to a remarkably calm son, said she believed her intentionally relaxed attitude during pregnancy paid off. After a stressful 24 hours when the newborn first did not breathe properly and then had to be treated for low sugar levels, 15-day-old Khan is now the dream baby.

He sleeps six hours at night and has only cried twice, both times just looking for a feed.

Mrs Simpson said her son's placid temperament was likely due to a mix of genetics -- dad is also amiable -- and the lengths she went to during pregnancy to relax.

The Griffith University exams officer worked part-time three days a week and stopped entirely five weeks before her due date. Every night she stepped in the bath with a book, a ritual she has continued post-birth.

"Remaining calm makes a huge difference," said Mrs Simpson.

Anyone interested in taking part in the study should call Judith Warner on 5552 9121.