SLR - April 2016 - Tyler Veldkamp

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

Dodwell E, Risoe P, Wright J. Factors Associated With Increased Risk of Clubfoot: A Norwegian National Cohort Analysis. J Pediatr Orthop. 2015 Dec; 35(8): e104-9. 

Scientific Literature Review
Reviewed By: Tyler Veldkamp, DPM
Residency Program: Hennepin County Medical Center
Podiatric Relevance: Clubfoot is a congenital deformity of the foot occurring at a rate of 1-2/1000 births, making it one of the most common congenital birth defects. Although numerous etiologies have been reviewed it is thought to be a combination of both genetic and environmental factors. Understanding and addressing modifiable risk factors may help to decrease the number of children born with this deformity. The goal of this study was to use a prospective national Norwegian cohort to investigate the demographic, socioeconomic, environmental, and familial risk factors of clubfoot.

Exposures prior and during pregnancy were identified through the Norwegian Mother and Child Cohort Study (MoBa) 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. Demographic, socioeconomic, parental medical history and environmental exposures before conception and during pregnancy were ascertained.

Results: One hundred and eight thousand, five hundred and thirty-five pregnancies were analyzed of which 121 cases of clubfoot were found (rate of 1.1 per 1000) with males accounting for 64 percent of the cases. Multivariate analysis showed parental clubfoot to have the strongest association with an odds ratio (OR) of 31.5. Cigarette smoking both three months before pregnancy (OR 1.82) and the first trimester (OR 2.67) was also significant. Also infants with solvent exposure had greater clubfoot risk (OR 1.66). Parental age, maternal weight, educational level, maternal alcohol use, mental illness, oligohydramnios, folic acid supplements, exposure to shift work, sauna use, disinfectants, season of birth, maternal anxiety or depression,  insecticides, paint, and diabetes were not associated with clubfoot in the adjusted analysis.

Conclusions: The study found that parental diagnosis of clubfoot, maternal smoking, and solvent exposure were the only statistically significant associations with clubfoot. This current prospective evaluation adds to our understanding of the etiology of clubfoot and in particular presents solvent exposure as a potential modifiable risk factor in addition to maternal smoking. One of the studies main strengths included the use of the Norwegian MoBa and NMBR which have highly detailed and reliable information on patient’s medical and parental medical history. Although a drawback is that only a proportion of Norwegian pregnancies are included in the MoBa database and they have been found to be a statistically healthier mother population. This raises the question on whether the results are an accurate representation of clubfoot etiology. Overall, I think the study confirms the well-accepted notion that familial trait and smoking associates highest with clubfoot deformity and also suggests that solvent exposure is a potential risk factor as well. I believe the article highlights the importance of public health initiatives to limit these modifiable risk factors for those considering conceiving in the future. The study also serves to dispel the notion of many of the other previously studied clubfoot risk factors. I believe the article can serve to help physicians when educating parents and patients on the known risk factors and etiologies surrounding clubfoot deformity.

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