livescience.com high number of birthdays in September popular birth month Centers for Disease Control and Prevention don’t quite know why LifeScience.com August is one of the top months babies born in the summer less likely to give birth in winter first and second highest number of births birth rate seasonality livescience.com less likely to give birth in winter April isn't far behind fecund more people are born in the month of August birth month data supposedly to warm up from winter’s cold first and second highest number of births August less likely to give birth in winter majority of American babies are born in the summer months