There will have been a lot written about stress in this month, but in psychology, the concept is hard to pin down. Is it how you feel? Is it the force that acts upon you? It’s not a satisfying term however, stress can be the cause of many things. Stress-related illnesses can include atherosclerosis (leading to heart attacks and strokes), allergies, asthma, clinical depression, clinical anxiety, colds, diabetes, colitis, chronic fatigue syndrome, fibromyalgia, eczema, ulcers, haemorrhoids. The list goes on.

One outcome that is relevant and increasingly a topic of research, particularly in the post-COVID-19 era is the impact of prenatal stress. This is the exposure of an expectant mother (and her unborn baby) to psychosocial and/or physical stress and the negative consequences this can have on the child. When the mother is under stress, this will result in the release of stress hormones – helping her to cope with the stressor at hand. But these circulating hormones can pass from mother to foetus through the placenta, affecting foetal development.

The classic example is from Project Ice Storm and the research by Suzanne King, a researcher at the Douglas Mental Health University Institute in Montreal. In January 1998, a terrible storm struck Southern Quebec, leaving up to 3 million Canadians without power in the coldest month of the year. Project Ice Storm recruited 150 families in which the mother was pregnant during this power cut, and the project was able to follow more than 100 of these families for nineteen years. Prenatal exposure to the Quebec ice storm has been linked to poor cognitive and language development and higher Body Mass Index.

Regardless of cause or length, exposure to disaster during pregnancy is associated with increased risk of adverse outcomes for unborn children, consequences of which can last their entire adult life. Most recently, we have faced the COVID-19 pandemic – sudden high impact lockdowns in Spring 2020, followed by a long period of distinct COVID variants, enforced mitigation measures, and repetitive bouts of social isolation and loneliness. Most certainly, exposure of pregnant women to the challenges of the pandemic will have had an effect.

Pre-natal stress can affect foetal development, particularly in the more vulnerable first and second trimesters when important brain development is taking place, leading to increased likelihood of conditions such as autism spectrum disorder, attention-deficit/hyperactivity disorder, and increased susceptibility to Post Traumatic Stress Disorder (PTSD) in later life, if exposed to further traumatic events. Normally, stress is reduced through friendly, positive interactions with family and friends, so the COVID-19 pandemic may be unique as a major life event which also disrupted these supportive relationships. Indeed, greater maternal fear of COVID-19 during pandemic pregnancies has been associated with a mean 192g reduction in birth weight and changes in infant mood at three months of age. Worse, the measures required by lockdown also resulted in limited access to healthcare, greater job insecurity, and increased exposure to domestic violence - long known as a predictor of low birth weight and premature birth.

This is all very negative.

However, there are valuable lessons which can be learnt. There is greater interest in providing programmes aimed at reducing anxiety in pregnant women – as pregnant women are up to three times as likely to be affected by anxiety in normal conditions – and these have been shown to be effective. Furthermore, research has shown expectant mothers are willing to engage in such sessions, whether this is Mindfulness, Cognitive Behavioural Therapy or something else. Large-scale stressors can have significant effect on unborn babies so in Stress Awareness Week, please spare a thought not just for friends and family, but those due to arrive later this year.

Dr James Jackson is a Chartered Psychologist and Associate Fellow of the British Psychological Society and a Reader in Biological Psychology at Leeds Trinity University.