21 August 2013

Quitting smoking leads to larger babies

Women who quit smoking when becoming pregnant are less likely to give birth to small babies than smokers, a new study suggests.


Women who quit smoking immediately before or after becoming pregnant gain more weight during and after pregnancy – but their babies are less likely to be born small than those born to smokers, a new study suggests.

Researchers in Denmark found that women who quit smoking gained about 2.7 kg during their pregnancies than those who continued to smoke and a similar amount in the year after giving birth. On the other hand, women who quit smoking early in pregnancy and non-smokers gave birth to babies of similar birth weights, on average.

 Babies of women who kept smoking were more likely to be born at a low weight. "The big thing to get out of this study is that quitting early in pregnancy is as helpful in respect to the birth weight of your baby as never having smoked while you were pregnant," Dr Amber Samuel, a maternal-foetal medicine expert at Emory University School of Medicine in Atlanta, said. "I think that can be an inspiration to moms who are looking to make a change in their lives.

"According to the American Cancer Society, between 10 and 15% of women smoke during pregnancy. Studies have linked smoking to premature birth and other complications, such as birth defects, low birth weight and stillbirth.

Higher risks

Infants have a three to four times higher risk of dying from sudden infant death syndrome, or "crib death", if their mothers smoke during and after pregnancy. Children exposed to second-hand smoke also have more ear infections, pneumonia, bronchitis, asthma and other health problems.

The new study included 1 774 women who were part of the "Smoke-free Newborn" study conducted in Copenhagen, Denmark, between 1996 and 1999. Twice during pregnancy, researchers surveyed women about their smoking status.

 To double-check whether women who said they quit smoking really did, their saliva was checked for cotinine created when nicotine is broken down in the body. About 38% of women were smokers before becoming pregnant, and half of them quit right before or soon after, Dr Line Rode of Copenhagen University Hospital and colleagues found.

During pregnancy, non-smokers gained almost 13.6 kg, on average; smokers gained 13.1 kg; and quitters gained 15.8 kg. Among women who quit smoking, 8% had babies born below the 10th percentile for birth weight, based on general Scandinavian records. In comparison, 22% of smokers had babies whose weight fell below that cut-off.

Babies with low birth weight are at higher risk for infections, breathing and respiratory disorders, delayed growth and social development and learning disabilities.

Extra weight

One year after giving birth, half of quitters were able to stay off cigarettes. Non-smokers and relapsed quitters both gained between 68 and 90 kg post-pregnancy; successful quitters gained 3.1 kg; and smokers lost about half a kilo, according to findings published in Obstetrics and Gynecology.

"One strength of the study is that it tried to ferret out whether women who say they quit smoking actually did quit," Samuel, who was not involved in the research, told Reuters Health. On the other hand, she said the results may not apply to the current US population. "There were very few obese women in this study," Samuel said.

According to the Institute of Medicine, women with a normal pre-pregnancy weight should gain between 11 and 15 kg during pregnancy and obese women should gain 4.9 to 9 kg. Excessive weight gain during pregnancy is linked to birth complications and medical problems for the mother, such as gestational diabetes.

Extra weight that stays on after pregnancy can increase a woman's risk for obesity, diabetes and heart disease. Samuel said most women in this study did not gain enough weight to offset the long-term benefits of not smoking.

She said it's not possible to put a time frame on how late into pregnancy a woman can quit smoking and still see benefits for her baby, since the researchers did not analyse their results based on when, exactly, women kicked the habit.


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