Marijuana, alcohol, cocaine, unless you are like 'alwaysthere' with a way to find out which isn't part of a biased survey (you know, listening to those 'anecdotes' the regular posters here at the R-G like to ignore) we are guessing at best.  

One of the stupidest statements is that sign required in every bar in Oregon "Alcohol and pregnancy don't mix." There are thousands and thousands of women, married or single who wouldn't have become pregnant except for alcohol.   

New Years?

"Perhaps unsurprisingly, September 12, 18, 25 and 26 - which are all around nine months after the holiday season - were found to be the most common days for births."