University of Minnesota Medical Center, Fairview, had a weekend string of 19 births that were all boys. The streak started at 9 p.m. Friday and ended with the birth of a girl around 7 a.m. Monday morning.

The hospital is planning a big to-do about this anomaly later this afternoon when the media can get pictures of some of the babies and learn some of the other trends -- like the number of the boys with common first names, etc. No word yet on whether any of them were named Chance ...

If you assume a 50-50 chance of a birth resulting in a boy or girl, then the odds of this happening 19 times in a row are something like 1 in 524,288. There is a 100% chance of a stats whiz correcting my crude math, though (1/2^(19)). There also is a problem with the assumption of a 50-50 chance. Though the disparity dipped a bit recently, more boys are born than girls in Minnesota and the U.S. each and every year.

This sex ratio, at least in theory, has to do with the fact that boys are more susceptible to infant deaths. So the birth of more boys might be nature's way of ensuring an equal number of men and women by their reproductive years. There are numerous theories about environmental factors disrupting this process. The state health web site mentions associations between smoking and pesticides and fewer male births. "Another environmental factor that may affect sex ratio is exposure to endocrine disruptors (e.g., phthalates), which decrease testosterone and can result in fewer male births."