According to Livescience.com, August is frequently the month when the most babies are born. This was determined based on U.S. birth data collected between 1990 and 2006 by the U.S. Centers for Disease Control and Prevention.
The article claims that this data is part of a larger historical trend in which the late-summer months of July, August and September see higher birth rates. The Livescience.com article also presents a CDC health statistics demographer's theory concerning the matter. The demographer suggests that temperature decreases in the winter leads to people spending a larger amount of time indoors, increasing the likelihood of conception and leading to a late summer birth.