Birth Defects Linked to Smoking While Pregnant

LONDON, UK, July 11, 2011 (ENS) – Pregnant women who smoke are much more likely to deliver babies with missing or deformed limbs, clubfoot, cleft palate and gastrointestinal problems than nonsmokers, finds the first study to identify the specific birth defects most associated with smoking.

The study by scientists at University College London was published today in the journal “Human Reproduction Update.”

Pregnant smoker (Photo by Havasmoke)

“People may think that few women still smoke when pregnant. But the reality is that, particularly in women under 20, the numbers are still staggeringly high,” said the study’s lead author Professor Allan Hackshaw, UCL Cancer Institute and member of the Royal College of Physicians Tobacco Advisory Group.

In the UK, 45 percent of women under 20 and 17 percent overall still smoke during pregnancy, according to 2006 figures from the Office for National Statistics, despite public health advice which warns of the harms of maternal smoking, such as miscarriage and premature birth.

In the United States, 20 percent of women aged under 25 years smoke during pregnancy, compared to nine percent among those aged over 35.

“The message from this research is that women should quit smoking before becoming pregnant, or very early on, to reduce the chance of having a baby with a serious and lifelong physical defect,” Professor Hackshaw said.

The authors examined a total of 172 research papers published over the last 50 years, which looked at a combined total of 174,000 cases of malformation alongside 11.7 million controls.

The risk was increased by 26 percent for having a baby with missing or deformed limbs, 28 percent for clubfoot, 27 percent for gastrointestinal defects, 33 percent for skull defects, 25 percent for eye defects, and 28 percent for cleft lip/palate.

The greatest increase in risk, 50 percent, was for a condition called gastroschisis, where parts of the stomach or intestines protrude through the skin.

Newborn in hospital for repair of gastroschisis (Photo by Alleycat-1964)

“Maternal smoking during pregnancy is a well established risk factor for miscarriage, low birthweight and premature birth,” said Professor Hackshaw. “However, very few public health educational policies mention birth defects when referring to smoking and those that do are not very specific. This is largely because of past uncertainty over which ones are directly linked.”

“Now we have this evidence, advice should be more explicit about the kinds of serious defects such as deformed limbs, and facial and gastrointestinal malformations that babies of mothers who smoke during pregnancy could suffer from,” he advised.

The research authors recommend that public health guidance should now be more explicit about the specific malformations associated with maternal smoking, in order to try and reduce the numbers of pregnant women who smoke.

Co-author, Professor Charles Rodeck, UCL Institute for Women’s Health, said, “The results of this research are of the greatest significance for the health of mothers and babies and for public health policy.”

“If the recommendations are implemented, they will lead to a reduction in the incidence of several common malformations, and also to greater efficacy of smoking prevention programs,” said Rodeck, “as the warning of a birth defect adds weight to that of a small or premature baby.”

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