[Eric A. Taylor (OP)]

Women have about 12 chances of becoming pregnant during any year, evenly distributed throughout the year. I'm wondering if more people are born in some parts of the year than others.

If there is a peek I'd expect it to be in the fall, September or October in the North May or June in the South, because these months fall 9 months after the coldest parts of the year when people are more likely to stay inside.

[Eric A. Taylor (OP)]

Women have about 12 chances of becoming pregnant during any year, evenly distributed throughout the year. I'm wondering if more people are born in some parts of the year than others.

If there is a peek I'd expect it to be in the fall, September or October in the North May or June in the South, because these months fall 9 months after the coldest parts of the year when people are more likely to stay inside.

Atmospheric, immediate geography and human social events do affect our behavior! Just concentrating on the Northern hemisphere, the USA as a focus, considering the southern is the reciprocal.
In your deductive reasoning,  I believe you hit the nail on the head.
Even though the pattern below focuses on a particular day the average usually has a statistical bandwidth in the unit of days. Some are certified documented studies, some educational guesses or quotes.

Festive Occasions promote good feelings, natural draw to human copulation
Uncomfortable surroundings, atmospheric conditions, whether it is weather or social inhibit.

“Frequency”
“According to a public record births database, birthdays in the United States are quite evenly distributed for the most part. However, there tend to be more births in September and October. This may be because there is holiday season nine months before. [7] October 5th is considered to be the most populous birthday in the United States. [8]”

http://en.wikipedia.org/wiki/Birthday
 
“So why October 5? Just a random date? Perhaps, but "Anybirthday" has a theory: To be born on this date, a baby would most likely have been conceived on New Year's Eve.
The survey also found May 22 to be the least common birthday”

http://ask.yahoo.com/20061114.html

I wasn't referring to "the south" as in the southern US (Georgia, Texas, Arkansas... I was referring to "the south" as in southern hemisphere (South Africa, Australia, Brazil...) By the way, Keith Urban, a very popular country singer is the "most southern" of ALL country singers on US country charts today. He's from Australia.

As for weather or other events. Christmas '08 saw some of the heaviest snow fall, and coldest weather the Portland, Or area has seen in 40 years. For more than 2 weeks the city was paralyzed by snow covered, icy roads. September 09' saw a HUGE upswing in births....wonder why.

Same is true of a huge blackout a few years back in New England. Millions left without power saw a 700% increase in births 9 months later.

But these are anomalies. I wonder if, in general, during the longer, colder nights of winter, when people spend more time inside, they get frisky. After all not everyone can enjoy the crap they put on TV.