Seasonality in birth defects, agricultural production and urban location.

This paper tests whether the strength of the "spring spike" in birth defects is related to agricultural production and urban location using Texas Birth Defects Registry data for the period 1996-2007. We find evidence of a spike in birth defects among children conceived in the spring and summer, but it is more pronounced in urban non-agricultural counties than in other types of counties. Furthermore, the spike lasts longer in urban non-agricultural counties as compared to other types of counties.