Smoking and the Fetus
- Chris Woolston, M.S.
- Posted March 11, 2013
A little more than three years ago, somebody forced Joy Dewell of Bozeman, Montana, to quit smoking. Dewell didn't particularly want to quit, and she might not have ever done it on her own. But as soon as her son, Elijah, became a part of her life, she knew smoking wasn't an option. It's amazing how persuasive people can be before they're even born.
After she discovered she was pregnant, Dewell, a coordinator for a middle-school mentoring program, bought a stack of books about pregnancy. They all confirmed what she already knew: Cigarettes and pregnancy just don't mix. As much as she longed for a cigarette, she vowed not to light up again. "You're the only one who can make the choice to quit smoking," she says. "The baby doesn't have a choice."
Gasping for air
It's not a choice to make lightly. Smoking throughout pregnancy doubles the chances that a baby will be born prematurely or have a low birth weight. Smoking also more than doubles the risk that an infant will die during, shortly after, or shortly before birth. And a study of nearly 15,000 young women in Australia found that smokers were twice as likely as others to suffer a miscarriage. Even if the baby is born healthy, there are other risks. Smoking during pregnancy also increases the risk of SIDS (Sudden Infant Death Syndrome), also known as crib death, and respiratory problems such as asthma.
At a time when doctors are making tremendous progress against all sorts of conditions that can complicate pregnancy, smoking still poses an enormous threat. "Of all of the things that can make a pregnancy high-risk, I worry more about mothers who smoke than mothers who have diabetes or hypertension," says Robert Welch, MD, the chairman of the Department of Obstetrics and Gynecology at Providence Hospital in Southfield, Michigan. When an expectant mother has a serious disease, he can usually give her medications to control the condition and protect the baby. But when a mother smokes, he says, he can only encourage her to quit. If she can't or won't give up her cigarettes, he just has to prepare for the consequences.
Even top-notch medical care can't compensate for the multiple effects of smoking on a developing baby. First and foremost, smoking cuts down a baby's supply of oxygen. A lack of oxygen hampers a fetus's growth and development, setting the stage for low birth weight, stillbirth, miscarriage, and many other potential complications.
Smoking reduces oxygen in two ways. Carbon monoxide in cigarette smoke quickly attaches to the baby's red blood cells, taking the place of oxygen. The more a woman smokes, the more carbon monoxide she delivers to her baby. As reported in the journal Drug and Alcohol Review, the carbon monoxide from a two-pack-a-day habit can cut a baby's oxygen supply by 60 percent. Nicotine makes matters worse by constricting the blood vessels throughout a woman's body, including the umbilical cord.
The more a woman smokes, the greater the risks to her baby. This is perhaps most clearly reflected in birth weight. On average, a woman who smokes a pack a day during pregnancy will cut about half a pound from her baby's birth weight. A two-pack-a-day habit could shave off an entire pound. But even one or two cigarettes each day aren't safe.
Welch says some mothers may welcome the prospect of a smaller baby, but stunted growth comes with consequences that may last a lifetime. "I tell mothers that small babies have small brains," he says. Smoking while pregnant may also cause subtle changes in children's brain development and behavior, partly because of hampered development in the womb, and partly because large doses of nicotine can damage brain cells. In addition, growth-restricted babies are more likely to have serious conditions such as diabetes and high blood pressure in adulthood.
Babies exposed to cigarettes during pregnancy may also have underdeveloped lungs. Some need to spend their first days or weeks attached to a respirator. Even after they leave the hospital, their breathing troubles may not be over. Babies whose mothers smoked during pregnancy are two to three times more likely than other babies to die of sudden infant death syndrome. (The risk may be even greater if the mother continues to smoke after the child is born.) And as the children grow older, they may be especially vulnerable to asthma.
Low birth weight, stillbirth, miscarriages, brain damage, weak lungs: Add it all up, and a pregnant smoker has only one real option. She needs to quit, and the sooner the better. If a woman can kick her habit before the 14th week of pregnancy, her chances for a healthy baby will be as good as anyone else's, Welch says. Around the 14th to the 16th week, developing babies go through a growth spurt that lasts until birth. If a woman is still smoking after this time, her baby will start lagging behind. Every day that her baby doesn't get a full supply of oxygen is another day that he won't grow and develop to his full potential. Even if a woman is still smoking in the 30th or 35th week of pregnancy, she can still give her baby a huge gift by quitting immediately. Five or 10 weeks of optimal growth are better than no weeks at all.
What about secondhand smoke?
Even if a pregnant mom doesn't smoke, every time someone else in her household smokes, she inhales toxic substances like arsenic, formaldehyde, and hydrogen cyanide. And what mom breathes, her baby breathes. A study by researchers at Columbia University found that two-year-olds whose mothers were exposed to secondhand smoke during pregnancy scored lower on cognitive development tests than kids from smoke-free homes. And that's not all. Breathing secondhand smoke during pregnancy exposes the fetus to many of the same risks that would result if the mother smoked, including low birth weight, premature birth, respiratory disorders, and increased risk of SIDS. Smoking is bad news for an unborn baby -- whether it comes from a cigarette in her mother's mouth, or smoke from someone nearby.
Carrying a torch for her baby
As Joy Dewell can attest, giving up smoking isn't easy, even when you have every motivation in the world. She was never a heavy smoker, but she did count on cigarettes to ease her stress and calm her nerves. And, in her case, discovering she was pregnant was very stressful. She and her husband hadn't actually intended to start a family just yet, and they weren't sure they were emotionally or financially ready. She felt like lighting up every time she thought about their savings account, but she knew she had to resist the urge. Each time a craving hit, she took a walk and reminded herself that someone was counting on her.
Her altruism didn't go unnoticed. Thanks to a nomination from a local tobacco control organization, Dewell got to run with the Olympic torch in 2002 as it made its way toward Salt Lake City for the winter games. Holding the torch was a great honor, but the real reward was bundled up in a snowsuit cheering his mom from the side of the road. Elijah is now a happy, healthy two-year-old, and he's about to become a big brother. Dewell still has all of those pregnancy books lying around, but she doesn't need to read them so carefully this time. She knows what to do -- and what not to do.
Interview with Joy Dewell, mother and ex-smoker.
Interview with Robert Welch, MD, chairman of the Department of Obstetrics and Gynecology at Providence Hospital in Southfield, Michigan.
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Kelly Shanahan, MD, an OB/GYN in private practice in Lake Tahoe, California, and author of Your Over-35 Week-By-Week Pregnancy Guide.