C-sections are allowing women to have their babies on their schedule nowadays. Because of that, it's not surprising that women may be picking certain dates over other dates to have their kids. A recent study of US birth certificates on a 10-year period suggests that women; whether through c-section or other more natural means, might be picking Valentine's day to have their kids.
The study found that there were 4% more birthdays on Valentine's day than there were on any day in the surrounding 2 weeks. Interestingly, they found a similar change on another holiday, months later. There were 5% LESS births on Halloween than in any other day surrounding it.