Seasonal Variations in Birth Weight in Suzhou Industrial Park.

Many environmental factors have been shown to adversely influence birth weight, and new insight has been gained into 'seasonal programming'. We studied a total of 23,064 infants. The mean birth weight varied across seasons. Logistic regression analysis was used to obtain the crude and adjusted odds ratios (ORs) for dichotomous outcomes (e.g., macrosomia, low birth weight). There were significant differences in the risks for macrosomia in infants born in different seasons. Compared with those for infants born in spring, the ORs for macrosomia were 0.85 [95% confidence interval (CI): 0.75-0.98] and 0.87 (95% CI: 0.77-0.99) for infants born in summer and autumn, respectively. These findings suggest that environmental factors may have public health implications and should be considered when primary prevention programs are developed for macrosomia or low birth weight.