Why is it more likely for babies to arrive in September?

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We’ve heard two jokes on clustered baby due dates from our clients:

  • November (9 months after Valentine’s Day)
  • 9 months after dad’s birthday (ha)

But now there’s new research indicating that September might be the most logical time for us to see more babies. Before we get into the why, let’s set up the methodology.

The methodology of the study

To investigate this question, researchers examined data from 130 countries, including records of sex-related Google searches from 2004 to 2014 and an analysis of collective moods revealed in public Twitter posts from 2010 to 2014. The study included data from both the southern and northern hemispheres and from majority Muslim nations as well as predominantly Christian countries that celebrate a December 25 Christmas.

OK. So Google/Twitter. Some limitations but not bad.

What did the study find?

Analysis of the Google searches found that online interest in sex peaks in both hemispheres during major cultural and religious celebrations: Christmas in predominantly Christian countries and Eid al-Fitr, the celebration that marks the end of Ramadan, in Muslim majority nations. The collective mood during these periods is relaxed and loving, an analysis of Twitter posts found.

Births peak nine months after Christmas or Eid al-Fitr, regardless of what hemisphere people lived in or how close their country was to the equator, which researchers believe means biological responses to changing seasons are not what’s driving reproductive urges.

Why would this be?

There are a couple of potentially logical reasons:

  • The mood is more loving/festive around the holidays
  • People have more time as work is less of a commitment usually
  • (can’t ignore this) There’s a lot of drinking at work/friend parties
  • It’s the end of a year and people naturally are thinking about resolutions and next steps and plans, and a baby is the biggest plan of them all

What’s your take?

Were you and your friends pregnant at the same time? Is there a cluster of birthdays in your neighborhood or school? Let us know. It’s kind of interesting to see.

What is the Massachusetts data like?

Here’s some available data for 2013. It doesn’t go month-by-month but there’s some interesting intel on the increase in C-Section and 30+ births to check out.

And to blow a small hole in the research above, the most popular birthday in Mass is actually June 27th. Between 2005 and 2014, an average of 232.2 people were born on June 27 each year.

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