According to recent studies, foetuses of pregnant women who work in hot, humid areas may exhibit indications of stress before their mothers. The study is the first to assess the effects of heat stress on the foetuses of manual labourers, and it involved 92 pregnant subsistence farmers in The Gambia. According to the results, there was a 17% increase in foetal strain for every degree Celsius in heat stress exposure, as seen by elevated foetal heart rate and slower blood flow through the umbilical cord.
Overall, the team, which was led by scientists from the Medical Research Council (MRC) Unit The Gambia at the London School of Hygiene & Tropical Medicine (LSHTM) and LSHTM, discovered that even a small increase in body temperature from performing manual labour in intense heat resulted in physiological strain in both the mother and foetus. The Lancet Planetary Health published the study.
Dr Ana Bonell, Wellcome Trust Global Health Clinical PhD Fellow at LSHTM and lead author, said: “Climate change has led to increasingly extreme temperatures worldwide and Sub-Saharan Africa is particularly vulnerable to climate impacts. Our study found that pregnant subsistence farmers in The Gambia commonly experience levels of extreme heat above recommended outdoor working limits, and that this can have significant effects on their health and the health of their babies. The results suggest we have to find effective interventions to protect these women and reduce adverse birth outcomes.”
Study author Jainaba Badjie from MRC The Gambia at LSHTM said: “Despite the growing scientific evidence linking maternal heat exposure to adverse birth outcomes, including premature birth, low birth weight, and still birth, up until now there has been little research into the physiological mechanisms responsible for these outcomes. We urgently need to understand these mechanisms so that we can find better ways to support mothers and babies in these conditions.”
Participants in West Kiang, The Gambia, were given wearable devices to track their maternal heart rate, skin temperature, and projected energy expenditure during field visits while being encouraged to go about their normal daily activities.
Fetal heart rate and umbilical artery blood flow were measured using portable ultrasound equipment at the beginning of each visit (which served as the baseline), midway through the worker’s shift, and finally at the end of the shift.
Additionally, data on maternal signs of heat sickness was gathered. Over half of the women said they had at least one of the following symptoms during field visits: nausea, vomiting, headache, dizziness, weakness, muscular aching, exhaustion, and dry mouth.
Data analysis revealed significant correlations between maternal heat strain, which was also connected to foetal strain, and exposure to heat stress. Even after correcting for maternal heat stress, foetal strain was still substantially correlated with maternal heat stress, indicating that other biological considerations are necessary.
The researchers propose that the redirection of blood from the placenta to the skin, which appears to occur at lower core temperatures than emphasised by other studies, is an essential physiological component to take into account in future study. The results also emphasise the need for more research to uncover and assess treatments that can assist Sub-Saharan African pregnant agricultural workers in becoming used to working in intense heat.
