New research from the UK suggests that our birth size and placenta weight may hold clues to the way the left and right sides of our brain will work in relation to each other in later life. These intriguing findings, presented in the journal PLoS ONE, may help to improve our understanding of a range of health issues linked to cerebral laterality.

The research was conducted at the University of Southampton and the Medical Research Council Lifecourse Epidemiology Unit at Southampton General Hospital in the UK. For the purposes of the study, the team analysed the neurological responses of 140 children at rest and in response to increased brain activity.

The children, aged 8 or 9, were asked to perform fun, creative tasks which also held an element of challenge - such as making up an exciting story and acting it out to a video camera. By monitoring fluctuations in the temperature of the tympanic membrane in the children's ears, the researchers were able to analyse the blood flow into different parts of the brain and to detect differences in the activity of the two sides. The results, as the team reports, notably suggest that stress unmasks inherent differences in cerebral laterality.

Correlating their findings with the children's birth weight and placenta weight, which had been recorded in the context of an earlier study presented in the journal PLoS ONE, the researchers observed that children who were born small, with relatively large placentas, were likely to show greater activity on the right side of the brain than the left. As the team explains, this specific pattern of brain activity has been linked with mood disorders such as depression.

This atypical placenta-to-foetus weight ratio can be caused by difficult conditions during pregnancy, for example when expecting mothers are exposed to high levels of stress. Limited availability of specific nutrients, which may stimulate the growth of the placenta as the mother's body tries to compensate for the thin supply to the foetus, is another likely cause - although this particular physiological response is associated with specific stages in the pregnancy.

These findings add to a wider body of research investigating links between adverse conditions during gestation and long-term changes in brain function. A mismatch between birth size and placenta weight is also thought to contribute to a proneness to conditions, such as hypertension, and stronger physical responses to stress in later life.