Estimation of the preventable proportion of congenital anomalies by selected risk factors in mothers: A case study in Iran

Worldwide, 1-6 percent of infants have at least one congenital anomaly that can lead to long-term consequences. This may have significant impacts on individuals, families, health-care systems, and societies. The aim of this study was to estimate the Population Attributable Fraction (PAF) of some congenital anomalies by three selected risk factors (obesity, diabetes and smoking) in the northwest of Iran and to estimate the number of preventable defects at birth in the population if we could reduce 50 percent of the exposure rate to these three risk factors at population level.

The regional data on smoking, obesity, and diabetes were entered in Population Estimate of Attributable Fraction of Congenital Conditions Everywhere (PEACE) software developed by International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR). It calculates the PAF for congenital anomalies attributed to exposure to those three risk factors.

This study showed that main anomalies attributed to "obesity" include Spina Bifida 40.1% (95% CI: 31.7-47.7), Hydrocephaly 26.8 (95% CI: 9.3-42.3) and Anencephaly 17.4 (95% CI: 1.6-31.9). The highest attributable defect to "smoking" was Cleft lip w/out Palate 5.8% (95% CI: 4.3-7.4), whereas for "diabetes" it was Tetralogy of Fallot 33.3 (95% CI: 17.2-49.5). A similar pattern was found when assumed in the model, the impact of 50 percent reduction in the exposure to each of the risk factors on preventable cases of birth defects in the population.

Obesity, diabetes, and smoking in women of childbearing age increased the risk of occurrence of congenital anomalies. However, obesity and diabetes had a remarkably greater impact compared to smoking. More studies are needed to investigate the role of passive smoking as a risk factor for the occurrence of birth defects.