A study carried out by Sarkar et al. at Imperial College, University of London and published in the scientific journal Clinical Endocrinology suggests that, if a mother is highly stressed during pregnancy, her consequent excessive production of stress hormones may adversely affect the brain development of her unborn child from about seventeen weeks after conception onwards.


The study involved 267 women and the researchers measured their levels of the stress hormone known as CORTISOL (which can have damaging effects over the long-term) by taking samples of their blood (levels of cortisol increase in the blood in accordance with increasing levels of stress and anxiety experienced by the individual).

The mothers also had samples of amniotic fluid (a protective fluid that surrounds the fetus and also facilitates the exchange of water, nutrients and biochemical products between the mother and the unborn child) taken.

It was found that mothers with high levels of cortisol in their blood also had higher than normal levels of the same hormone in their amniotic fluid (to which, as alluded to above, the unborn child is exposed).

Furthermore, it was found that the longer the mother had been pregnant, the stronger was the positive correlation between the levels of cortisol in her blood and the level of cortisol in the amniotic fluid.

This, in turn, suggests that the longer the mother has been pregnant (i.e. as the gestational age of the unborn child increases) the more he or she (i.e. the unborn baby) is likely to be adversely affected by excessive cortisol levels.

It should be noted, however, that further research is needed to clarify how high the mother’s cortisol levels need to be to present the unborn child with a significant risk of potential harm.


Such potential harm may include a lowering of the developing child’s potential I.Q. by about 10 points (Glover), an increased likelihood of developing attentional deficits and greater susceptibility to experience anxiety in later life (although, again, further research is needed in order to investigate these possibilities more fully).


From the above findings, it is possible to conclude that high levels of maternal stress may start to adversely affect the unborn child’s development from as early as a gestational age of 17 weeks and that this danger increases as the unborn child’s gestational age increases. It is therefore very important that the mother-to-be is provided with good emotional support during pregnancy, including sensitive treatment by employees.


P. Sarkar et al., Clinical Endocrinology. Ontogeny of foetal exposure to maternal cortisol using mid-trimester amniotic fluid as a biomarker. First published: 13 February 2007. https://doi.org/10.1111/j.1365-2265.2007.02785.x



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David Hosier BSc Hons; MSc; PGDE(FAHE).