Factors Associated With Increased Risk of Clubfoot: A Norwegian National Cohort Analysis

Background: Previous studies investigating the causes of clubfoot have shown conflicting results, potentially because of retrospective study designs or incomplete assessment of causative factors. The study aim was to examine risk factors for clubfoot in a large prospective Norwegian cohort. Methods: Exposures prior and during pregnancy were identified through the Norwegian Mother and Child Cohort Study (Mo-Ba) conducted by the Norwegian Institute of Public Health. This was linked to the Norwegian Medical Birth Registry, which provided clubfoot diagnosis through ICD-10 code Q66.0. Logistic regression analysis investigated associations between potential risk factors and development of clubfoot. Results: A total of 121 clubfoot cases were identified; 1.1 per 1000 births. Parental diagnosis of clubfoot [odds ratio (OR): 31.5; 95% confidence interval (CI): 9.61-103.3] and cigarette smoking, both in the three months prior to pregnancy (OR: 1.82; 95% CI: 1.05-3.18) and the first trimester (OR: 2.67; 95% CI: 1.28-5.55) were associated with clubfoot. Infants with clubfoot had greater solvent exposure (OR: 1.66; 95% CI: 1.00-2.76). Oligohydramnios, parental age, parental education, parity, maternal anxiety or depression, alcohol use, season of birth did not have statistically significant associations. Conclusions: In addition to parental diagnosis of clubfoot, results confirm the previously reported association between clubfoot and smoking, and counter previous evidence supporting season of birth, parental education, and other risk factors. Further studies are needed to investigate solvent exposure as a risk factor for clubfoot. Exposure to smoke and solvents can be controlled; this study highlights the importance of public health initiatives to limit these exposures both during pregnancy and in those considering conceiving in the future.