[roccman]

http://npr.tumblr.com/post/23169208430/ ... four-of-my

[steam_cannon]

This may be true. To quote an article, it seems "when the sun shines for about 12 hours and the temperature hovers between 50 and 70 degrees Farenheit" that people are most likely to conceive. Though with modern lighting and temperature control, this trend is blurring. These modern conditions may be causing disruptions to hormone cycles as well.

Article:
$this->bbcode_second_pass_quote('New York Times', '[')url=http://www.nytimes.com/1990/10/02/science/seasons-sway-human-birth-rates.html?pagewanted=all&src=pm]Seasons Sway Human Birth Rates[/url]

According to the new analysis, the perfect time of year to conceive is when the sun shines for about 12 hours and the temperature hovers between 50 and 70 degrees Farenheit. For reasons that remain mysterious, such conditions somehow help stimulate either ovulation in women, a burst of sperm production in men or a combination of the two.

In some regions of the world, the scientists say, people mating in the optimal fertility season have twice the chance of conceiving that they might have the rest of the year...

[Quinny]

Seems more likely to me that people get pissed up at xmas and new year parties.

[dolanbaker]

$this->bbcode_second_pass_quote('Quinny', 'S')eems more likely to me that people get pissed up at xmas and new year parties.

[radon]

Maybe have to do with the fact that historically the newborn have had a greater chance of survival if they were born during the summer season.

[JohnRM]

I think; In the common era, people are just inside more as October, November, and December roll around and they find themselves in the house more. It is probably no more complicated than that.

[knowres]

This must be US statistics... See the artificial low on July 4th/5th ? Also very low rates around the x-mas holidays... Can you find any more dates of national "importance" ....
hint: February 14th

[MD]

The summer/fall birth wave is easy to explain as it's nice months after the harvest.

The July 4th anomaly is not so easy to explain without giving birth mothers the ability to delay their labors for a day or two, which is not unthinkable.

[radon]

Is this the world's or US statistics? Who cares about the harvest time in the US.