What happens when pregnant women smoke?

Smoking during pregnancy can increase a woman's risk of miscarriage. See more drug pictures.
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By now, most people agree that smoking is not a grand idea for anyone. It's pretty easy to come up with a list of all the health problems that can afflict people who smoke cigarettes:

  • sinus problems
  • difficulty breathing and eventually, emphysema
  • cancer
  • increased risk of heart disease
  • increased risk of stroke

Most of the damage caused by cigarette smoking doesn't appear for years or decades, making it difficult to convince smokers to give up their habit. However, when a pregnant woman smokes, the nicotine and other compounds found in tobacco pose both an immediate and an extended threat to the health of her developing child. These dangers include:


  • Increased risk of miscarriage
  • Increased risk of Sudden Infant Death Syndrome (SIDS)
  • Premature birth
  • Low birth weight
  • Behavioral problems (i.e., hyperactivity)
  • Reduced verbal and mathematical ability

Ironically enough, smoking even reduces a woman's chance of even getting pregnant in the first place! How does smoking wreak so much havoc in only nine months? The difference lies in three things.  See the next page to learn more.




The Timing of Exposure

Some pretty spectacular changes occur over nine months of pregnancy. A newly fertilized, single cell morphs into a complex, specialized, self-conscious organism. Cells don't just have to multiply in number; they also change their appearance and how they work in order to form all of the different tissues and organs that make up the human body. The whole process is highly regulated; changes must occur at the right time and in the right place. In some areas of the developing brain, exposure to nicotine messes up this orderly progression.

How can nicotine from a few cigarettes (or even from a nicotinin how similar nicotine's action is to that of the native neurotransmitter, acetylce replacement patch) have such a profound effect? The answer lies holine. During the development of the brain, each neurotransmitter acting through its own receptor can tell a neuron to start or stop dividing, to differentiate, to form connections with other cells and even to die. How the neuron interprets stimulation by the neurotransmitter depends on the context in which it occurs. A signal at the wrong time can miswire whole regions of the brain. Because nicotine binds to cholinergic receptors, it can stimulate them just like acetylcholine. But unlike acetylcholine, nicotine is not regulated internally; the neurons see it whenever mom smokes another cigarette. Depending on when during brain development exposure occurs, nicotine can reduce the number of neurons in a brain region or change the way the neurons signal. Neither of these options is particularly appetizing when you think about it.


The Way Pregnancy Works

A developing child is also wholly dependent on its mother's body to:

  • supply nutrients
  • provide oxygen
  • remove waste products like carbon dioxide (CO2)

Because of this relationship, changes in how the mother's body works have consequences for the fetus. If you've read How Nicotine Works, you know that just the nicotine in cigarettes alters a smoker's blood pressure, heart rate, and even their metabolism. The other constituents of cigarette smoke, such as carbon monoxide (CO), can also change or interrupt basic physiological processes. CO is an odorless, colorless gas produced by burning carbon containing compounds. Combusting fuel in a car engine, for example, produces a lot of carbon monoxide. CO displaces oxygen from the molecule that normally carries it through your bloodstream to your organs and tissues. High levels of CO can be deadly; you simply can't provide enough oxygen to maintain cellular processes throughout the body, which is why you shouldn't sit idling in a closed-up car for too long! When a pregnant woman smokes, the trace amounts of CO that she inhales mean less oxygen will be delivered to her tissues and to her fetus.


Toxic Chemicals

When a pregnant women inhales cigarette smoke, she exposes herself and her fetus to harmful chemicals.
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The Incredible Number of Chemicals in Tobacco Smoke

There are more than 4,000 different compounds in your typical cigarette. Some of these compounds occur naturally in the tobacco plant, while others are added during the manufacturing process to add flavor or as preservatives. There is also a whole slew of chemicals created by combustion after you light a cigarette.

Many chemicals, including nicotine, can readily move from the mother's bloodstream into the fetal blood supply. (This is why physicians are so cautious about what over-the-counter or prescription drugs women take when they're expecting a child.) When a pregnant women inhales cigarette smoke, she exposes herself and her fetus to:


  • Nicotine - If you smoke while pregnant, your child will be exposed to almost the same level of nicotine as you. That means that once he or she is born and is no longer getting nicotine intravenously, the symptoms of nicotine withdrawal will likely set in.
  • Cyanide - Those who are old enough will remember the panic that ensued after someone laced Tylenol with cyanide back in the 1980s. Cyanide prevents cells from using oxygen for various metabolic processes, and it's one of the most deadly poisons around.
  • Cadmium - Found in rechargeable batteries, this heavy metal damages your kidneys. Without proper filtration and excretion by the kidneys, waste products from different cellular processes build up in your blood.
  • Arsenic - another heavy metal that interferes with the conversion of food (glucose) to fuel (ATP) inside your cells.
  • Formaldehyde - locks proteins in a rigid conformation. (For more information on formaldehyde, see Will aspartame make me go blind?)

With the exception of nicotine, there's not enough of any these chemicals in cigarette smoke to cause severe damage to either the smoker or their baby. It's more likely that all of these compounds in combination have the net effect of reducing the pool of nutrients and other resources that the fetus needs to grow. This may be one reason why babies born to smokers are smaller than average.