London : British scientists have found that long-term stress experienced by mothers during pregnancy adversely affects their unborn babies.
Researchers led by Vivette Glover at London's Imperial College studied 267 women, taking a blood sample from the mother and a sample from the amniotic fluid surrounding the baby.
They measured levels of a stress hormone called cortisol in both samples. At the age of 17 weeks and older, they found the higher the level of cortisol in the mother's blood, the greater the level of cortisol in the amniotic fluid, said a report published Thursday in the British Journal of Clinical Endocrinology.
"This is an important study as for the first time, there is solid evidence to show that an unborn child may be exposed to maternal stress as early as 17 weeks in development," the scientists said.
Amniotic fluid is a protective fluid that surrounds the foetus and reflects the exposure of the unborn child to various substances including hormones.
Stress hormones were a reaction to anxiety and useful in the short term because they helped the body deal with stressful situations, the online edition of BBC News reported.
However, if the stress goes on for a long time, the hormones can affect people's health leading to tiredness, depression and illness, a scientist involved in the study said.
This in turn can lead to health problems such as headaches, upset stomach, rashes, insomnia, ulcers, high blood pressure, heart disease, and stroke.
"We now need to carry out further work to unravel the mechanisms by which maternal stress affects the foetus, both during foetal life and into childhood," the scientist added.
Previous studies have suggested stress hormones activated by maternal anxiety may have a long-term effect on the child's brain development and future behaviour.
It had found babies exposed to the highest levels of cortisol while in the womb had lower intelligent quotients (IQ) at 18 months, compared with the infants of mothers who were less stressed.
Studies have also shown that children of highly stressed and anxious pregnant women were at double the risk of hyperactivity and attention deficit hyperactivity disorder (ADHD) at the age of four.
"For now, based on previous research, one thing is clear – high levels of stress in pregnancy can, in some cases, be detrimental to the health of the baby," scientists said after the latest study was published.
"To remain as stress-free as possible is certainly important during pregnancy. Of course, this is easier said than done as pregnancy itself can incite all sorts of feelings like feeling overwhelmed, happy and nervous," the study said.
Pregnancy can signify major emotional changes in mums-to-be, from mood swings to feeling incredibly anxious, which may well elevate women's stress levels. However, scientists said it is vital that pregnant women are given adequate support and reassurance from their family, friends and employers, to ensure they have a happy and healthy pregnancy.