Smoking during pregnancy tied to increased infant fracture risk
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Children born to mothers who smoked in early pregnancy were more likely to experience a fracture before age 1 year than those born to mothers who did not smoke, according to findings from a national register study published in BMJ.
“Smoking during pregnancy is a well-known risk factor for fetal growth restriction and low infant birth weight, but whether it influences offspring bone health and fracture risk after birth and later in life during childhood and early adulthood is less well understood,” Judith Brand, PhD, epidemiologist and researcher in the department of clinical epidemiology and biostatistics in the School of Medical Sciences at Örebro University in Sweden, told Healio. “To inform public health policies about the importance of early life factors in disease risk and prevention, it is important to determine if prenatal exposure to smoking influences the risk of fractures, and whether this is a long-lasting effect or not.”
Brand and colleagues evaluated fracture rates across 21.1 years of median follow-up among 377,367 individuals whose mothers smoked during pregnancy (48.5% girls) and 1,302,940 individuals whose mothers did not smoke (48.6% girls). Sweden’s Medical Birth Register and National Patient Register provided data on maternal smoking and fractures among the offspring. Maternal smoking was self-reported during the antenatal visit as nonsmoking, smoking between one and nine cigarettes per day or smoking at least 10 cigarettes per day.
There were 377,970 fractures among all individuals in the study. There were 1.59 fractures per 1,000 person-years from birth to age 1 year among those whose mothers smoked and 1.28 per 1,000 person-years for those whose mothers did not. The risk for a fracture from birth to age 1 year was 27% higher for those born to mothers who smoked vs. those born to mothers who did not (HR = 1.27; 95% CI, 1.12-1.45). In addition, those born to mothers who smoked between one and nine cigarettes per day were at 20% greater risk (HR = 1.2; 95% CI, 1.03-1.39) and those born to mothers who smoked at least 10 cigarettes per day were at 41% greater risk (HR = 1.41; 95% CI, 1.18-1.69), indicating a “dose dependent pattern.”
The risk for fractures was also greater for those aged 5 to 14 years (HR = 1.07; 95% CI, 1.05-1.08) and for those 15 years or older (HR = 1.11; 95% CI, 1.09-1.12) whose mothers smoked vs. those whose mothers did not, but there was no “clear dose-dependent gradient,” and the association at these ages did not persist after controlling for both measured and unmeasured confounding factors. In addition, the researchers wrote that at age 1 to 5 years, fracture risk was not associated with maternal smoking.
“From a public health perspective, our results suggest that tobacco-control programs which help reproductive-age and pregnant women to stop smoking are not only effective in reducing risks of adverse pregnancy outcomes, such as low infant birth weight, but may also prevent some babies from suffering a fracture during their first year of life,” Brand said. “This is also information that can used to further support smoking cessation among women.” – by Phil Neuffer
For more information:
Judith Brand, PhD, can be reached at judith.brand@regionorebrolan.se.
Disclosures: This study was supported by the Örebro University Hospital Research Foundation Nyckelfonden and the UK Economic and Social Research Council, UK Medical Research Council and the National Institute for Health Research. Brand reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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