These Are the Most Common Birthdays—And the Least

Turns out, the holidays are a very popular time to conceive, but not to give birth, according to real birth data.

Knowing your due date means knowing a whole lot more than when you can expect your little one to arrive. It could determine anything and everything from the logistics around your labor and delivery to the time of year your child can expect to celebrate their birthday.

Curious if your kid on the way will be celebrating during the most common birthday month and therefore have plenty of classmates celebrating, as well? Or maybe they'll be born on the least common day of the year for babies to make their big entrance into the world? Now you can figure that out, thanks to a viral blog post from The Daily Viz's Matt Stiles.

Here's the scoop on the most common birthdays in the U.S.

The Most Common Birth Month

Using real birth data from the U.S. National Center for Health Statistics and U.S. Social Security Administration, gathered by FiveThirtyEight, that covers 20 years of American births, Stiles concluded that September is the most popular month to give birth to a child in the U.S. In fact, nine of the top 10 days to give birth fall between September 9 and September 20.

So, then, the question is of course, why?

"If you back up 38 weeks, that means many couples are conceiving in December and around the holidays," explains Whitney Casares, M.D., M.P.H., F.A.A.P, author of The New Baby Blueprint: Caring for You and Your Little One. "It makes sense that they may be more likely to conceive during more celebratory seasons."

Another reason, Dr. Casares points out: According to a study in Obstetrics and Gynecology, couples may have more luck conceiving during the winter season due to higher-quality sperm in winter versus summer months. "They also postulated that changes in daylight length might make an ovum’s environment better-suited for a sperm," she notes. "More research is needed to understand this interesting phenomenon.

The Most Common Birthdays

Experian landed on September 9 as the most common birthday. It's one shared by Adam Sandler and Hugh Grant, jazz singer Michael Bublé, Russian literary giant Leo Tolstoy, and Colonel Sanders, the founder of KFC. September 19 is second most common birthday, followed by September 12, September 17, September 10, and the first non-September date in the mix: July 7.

The Least Common Birthdays

Christmas Day is the least common), while New Year's Day is the second to least common. Thanksgiving and the Fourth of July also rank low on the list. And perhaps because summer conceptions aren't as common as winter ones, April 20 is the 328th most common.

So if you happen to be expecting around the holidays, your child likely won't have all that much competition for celebration in the classroom growing up. But if you happened to conceive during the holidays, well, get ready for an avalanche of cupcakes and many performances of the "Birthday Song" come September.

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