Studies indicate that (on average) winter babies (born in January, Febuary or March) grow up to be "less educated, less intelligent, less healthy and lower paid" than those born in other seasons.
There have been a wide variety of suggestions as to why this happens, including weather and school age cutoffs. But new research suggests that the mother is actually the root of the problem! Economists have found that these winter babies are more likely to have mothers who are unmarried teenagers who lack a high-school diploma. Thus, being born to a woman of lower socioeconomic status, not their month of birth, is what puts winter babies at a disadvantage. The study suggests several reasons why there is a correlation between unmarried teenagers and winter babies, but one of them is quite interesting: prom. Turns out that winter occurs about 9 months after high school proms :)