But the evidence from animals is quite clear. Prenatal stress has a long term effect on the offspring. It is possible to foster the newborn rat of a stressed mother to a new mother, on the first day after birth and compare their behaviour as they grow up with that of a newborn rat whose mother was not stressed in pregnancy. One method used is shown in the diagram. The pregnant rat is stressed by exposing her to the smell of a cat.
Animal experiments have shown that prenatal stress can cause all the following effects on the offspring:
- More anxiety
- Reduced attention
- Learning deficits
- Less difference in function between the left and right sides of the brain
- Effects different on male and female offspring
- Altered sexual behaviour – males show homosexual behaviour and females are less nurturing mothers.
Importantly, all these effects have also been demonstrated in humans, except for the alterations in sexual behaviour.