Carbon Monoxide Poisoning in the Setting of Your Pregnancy

Carbon monoxide (CO) is a colorless, odorless gas that is produced following incomplete combustion of organic chemicals (chemicals whose molecules are structured based on carbon atoms), such as gasoline, coal, or wax. Each molecule of CO is comprised of one atom of oxygen and another atom of carbon. This structure affects the arrangement of electrons of CO molecules such that CO substitutes for molecular oxygen (O2) in attaching to what are called “heme” molecules. Heme compounds include a compound within red blood cells (RBCs) called hemoglobin (Hb). They also include various other compounds, such myoglobin (which stores O2 in muscle cells), neuroglobin (the O2-storing molecule nerve cells), and various molecules that enable energy generation within body cell power plants known as mitochondria. CO sticks much more strongly than O2 to heme molecules, which prevents O2 from doing what it needs to do in the body. This means that CO is a poison. CO poisoning, or toxicity, typically results from an acute CO exposure, meaning exposure to a lot of CO all at once. This can occur during pregnancy, when you are more susceptible to the effects of CO exposure than when you are not pregnant.

Regardless of how far you are into pregnancy–first, second, or third trimester–it is important to avoid carbon monoxide exposure.

Symptoms of CO poisoning

The symptoms of CO poisoning include dizziness, headache, nausea and vomiting, fatigue, breathing problems, movement problems, confusion, changes in consciousness, and loss of consciousness. These symptoms can develop in many other conditions–they are not specific to CO poisoning. This means that the key to recognizing CO poisoning is knowing that the victim has experienced possible CO exposure. For instance, you might know that the person was exposed to something burning inside a house.

CO toxicity can kill quickly if not recognized quickly and treated. By measuring levels of a chemical called carboxyhemoglobin in your blood, doctors can determine the level of severity of your CO poisoning. The treatment is hyperbaric oxygen therapy (HBO2) if the CO toxicity is severe; this requires a special chamber, which not all hospitals have. If the condition is mild, the victim can be treated with normobaric oxygen which means 100 percent O2, given at normal atmospheric pressure. Generally, people who are treated for severe CO poisoning must spend some time in the intensive care unit.

What are safe amounts of CO?

Generally, if the concentration of CO is 70 parts per million (ppm) or lower, most people are not in danger, but if you are pregnant, CO levels significantly lower than 70 ppm are needed. As for getting pregnant in the first place, there is some concern that exposure to CO in tobacco smoke is one of the reasons why tobacco smoking reduces fertility. In such cases, we are not talking about acute CO poisoning, but what’s called chronic CO poisoning–gradual poisoning from CO that harms the body gradually over time, without killing the victim quickly. Based on research involving tobacco and pigs, doctors and scientists also are concerned that CO exposure may cause spontaneous abortions (miscarriage). There also have been reports of maternal CO poisoning leading to stillbirth and also neurological problems in the baby, such as cerebral palsy.

CO poisoning during pregnancy and breastfeeding

Regardless of how far you are into pregnancy–first, second, or third trimester–it is important to avoid CO exposure. Although all of this may sound scary, following many cases of maternal acute or chronic CO poisoning, babies have come out just fine. However, given the risk of neurological problems, any suspected CO poisoning must be treated.

Although CO poisoning does make breast milk dangerous for the baby, if you suffer from acute CO poisoning, it is unlikely that you will breastfeed until you are treated.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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