Pregnant women are at a greater risk of carbon monoxide poisoning due to several factors related to the physiological changes that occur during pregnancy.
Carbon monoxide can have adverse effects on both the mother and the developing foetus. Pregnant women should take extra precautions to avoid carbon monoxide exposure to protect their health and the health of their unborn child.
Why are pregnant women and the foetus at particular risk?
Increased Oxygen Demand
During pregnancy, there is an increased demand for oxygen to support the growing foetus. Carbon monoxide competes with oxygen for binding to haemoglobin in the blood, potentially leading to decreased oxygen delivery to vital tissues, including the placenta.
Changes in Haemoglobin Levels
Pregnancy is associated with changes in blood volume and haemoglobin levels. The increased blood volume can lead to a higher amount of circulating carbon monoxide, and changes in haemoglobin levels may affect the body's ability to transport oxygen.
Impaired Oxygen Transport to Foetus
Carbon monoxide can readily cross the placenta, exposing the developing foetus. The affinity of foetal haemoglobin for carbon monoxide is higher than that of maternal haemoglobin, making the foetus more susceptible to carbon monoxide-related oxygen deprivation.
Foetal Vulnerability
The developing foetus is particularly vulnerable to the effects of carbon monoxide because organs and tissues are rapidly forming. Oxygen is crucial for proper foetal development, and any disruption in oxygen supply can have lasting consequences.
Risk of Preterm Birth
Carbon monoxide exposure during pregnancy has been associated with an increased risk of preterm birth. Preterm birth can lead to a range of health issues for the newborn, including respiratory and developmental complications.
Neurological Effects on the Foetus
Carbon monoxide exposure during pregnancy can have neurotoxic effects on the developing foetal brain. This may contribute to cognitive and developmental challenges in the child.
Maternal Health Risks
Pregnant women may experience more severe health consequences from carbon monoxide exposure due to the physiological changes associated with pregnancy. These changes can affect the cardiovascular and respiratory systems, increasing the impact of carbon monoxide on maternal health.
Symptoms Mimic Pregnancy Symptoms
The symptoms of carbon monoxide poisoning, such as headaches, dizziness, and nausea, can mimic common pregnancy symptoms. This similarity may result in delayed recognition of carbon monoxide exposure, as symptoms may be attributed to pregnancy rather than poisoning.
Foetal and neonatal death, congenital malformations and neurological problems occur with moderate to severe maternal exposure to carbon monoxide.
Studies conclude that at lower levels of exposure, adverse outcomes for the baby cannot be excluded. Washout of carbon monoxide from foetal blood takes longer than in adults, this and the lower partial pressure of oxygen in foetal blood and the relative hypoxia increase the effects of foetal exposure.
No focus had been given to assessing the environmental exposure of pregnant women to carbon monoxide in the UK. To address this the CO Research Trust has provided grants to a number of projects focused on this area:
Manchester Metropolitan University have two CORT funded projects under way which are looking ta the impacts of CO on effects of environmental carbon monoxide exposure on the developing cardiovascular system during pregnancy
Find out more about the projects: 'Characterising the cell-specific effects of low-level carbon monoxide exposure during vertebrate cardiac development'.
Sheffield Hallam University are looking at the impacts of low-level CO exposure on the adult and developing brain. Learn more about their work.
In 2020 iPiP was awarded a grant for a study looking at the exposure of pregnant women in their homes.
The literature review, highlights just how dangerous CO exposure can be in pregnancy.
It links exposure not only to foetal and neonatal death, but also to congenital malformations and long-term neurological problems.
Evidence also points to a potential connection with cardiac disease and dementia, as well as affecting those with underlying conditions and other health inequalities.
Perhaps most importantly, the review confirmed that chronic low-level exposure, which is often undetected, can cause significant harm to both unborn babies and vulnerable adults.
The IPPCO Study, one of the first to measure CO exposure in the homes of pregnant women, produced some important findings:
57.8% of homes had detectable CO levels
31.7% recorded levels above 4ppm, and 14.3% exceeded 10ppm
Several households surpassed WHO recommended limits
44% of homes did not have a working CO alarm
Beyond the data, the study provided important insights into perceptions of risk amongst pregnant women. Many women assumed CO exposure “wouldn’t happen to them,” and healthcare professionals identified the urgent need for a system-wide response.
An academic paper from this research has now been published in the BMC Pregnancy and Childbirth Journal, with more to follow; offering an evidence base that can no longer be ignored.
Turning Research into Resources
However, good research is just the beginning. To make a real difference, these findings need to be translated into tools that professionals can use.
CORT funded the UK Health Security Agency (UKHSA) to develop and pilot a CO exposure algorithm for midwives — a practical decision-support tool to help maternity teams identify, respond to, and prevent harm during antenatal appointments . This updated guidance has now published and is live for all healthcare professionals to access, to see it in action visit - https://www.gov.uk/government/publications/carbon-monoxide-co-antenatal-checks-algorithm-for-midwives
At the same time, iPiP partnered with NHS England’s e-Learning for Healthcare (elfh) team to create a suite of four online training modules. These sessions, designed for health and social care professionals, aim to increase awareness and confidence in recognising and responding to CO exposure. The piloting of the modules has now concluded and they are being readied for a national launch.
Furthermore, iPiP has been working with Fire and Rescue Services and maternity teams in Warwickshire and the West Midlands to evaluate a referral pathway for pregnant women at risk of exposure. The results have informed the development of a national implementation toolkit so this approach can be adopted more widely.