HealthDay News — Prenatal exposure to maternal smoking is associated with an increased fracture rate before age 1, according to a study published online Jan. 29 in The BMJ.

Judith S. Brand, Ph.D., from Örebro University in Sweden, and colleagues examined the impact of maternal smoking during pregnancy on fractures in offspring. Data were included from 1,680,307 people born in Sweden between 1983 and 2000 to 377,367 women who smoked and 1,302,940 who did not.

The researchers observed 377,970 fractures during a median follow-up of 21.1 years (overall incidence rate for fracture standardized by calendar year of birth, 11.8 per 1,000 person-years). There was a difference in the association between maternal smoking during pregnancy and risk for fracture in offspring by attained age. In the entire cohort, maternal smoking correlated with an increased rate of fractures before age 1 year (birth year standardized fracture rates in those exposed and unexposed to maternal smoking, 1.59 and 1.28 per 1,000 person-years, respectively). The hazard ratio for maternal smoking versus no smoking was 1.27 after adjustment for potential confounders.

A dose-dependent pattern was observed (hazard ratios, 1.20 and 1.41 for one to nine and 10 or more cigarettes/day, respectively, versus no smoking). The correlation persisted in within-sibship comparisons (hazard ratio, 1.58), with wider confidence intervals.

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“The results of this study indicate that maternal smoking during pregnancy is associated with an increased risk of fractures before 1 year of age,” the authors write. “Prenatal exposure to cigarette smoke, however, does not seem to have a longer lasting biological influence on risk of fracture later in childhood and up to early adulthood.”

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