Summertime Mystery: More Born, Fewer Die in August

Aug. 16, 2005 — -- This is the time of year when the storks get a workout and the grim reaper can let his minions schedule a vacation.

It's August -- the height of baby season, and the time of year when Americans are least likely to die.

"There's no if, ands or buts," said Beth Ann Roberts, nurse manager of labor and delivery at Baptist Hospital in Miami. "We have a definite influx [of babies] when it comes -- July, August, September."

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In most recent years, August and September are the top months for births in the United States, according to federal statistics.

August had the most total births every year from 1990 to 2002 except for four -- 1992, 1993, 1997 and 1998 -- when it was edged out by July.

September, a day shorter than July and August, averaged the most births per day over the period from 1990 to 2002. (Click HERE for a table of month-by-month births.)

Demographers and sociologists long have puzzled over the mysteries of America's birth seasons: Why do births peak in the fall almost every year, and then dip in January and again in April? Why do other parts of the world have their own repetitive patterns, in some cases practically the opposite of America's? And why do birth seasons occasionally change over time?

"There is no consensus that I'm aware of as far as a factor, or the factors, that contribute to this," said Brady Hamilton, a statistician and demographer for the reproductive statistics branch of the National Center for Health Statistics. "It seems to be a myriad of different hypotheses."

Officials are far more settled on why deaths tend to dip at this time of year and surge again in the winter months. On a day-by-day basis, August has the fewest deaths, while January has the most. (Click above for a table of month-by-month deaths.)

"This is consistent with what we know about the effects of winter and the flu season on those that are sick and frail," said Robert N. Anderson, chief of the NCHS's mortality statistics branch.

Deaths are fairly evenly distributed over the days of the week, Anderson said, with a barely perceptible increase on weekends, perhaps attributable to factors like alcohol and accidents.

Births, on the other hand, vary more by day of the week. They're most common on Tuesdays, and least common on weekends. The weekly pattern seems to be caused by doctors scheduling induced births and ceasareans early in the week, and clearing the slate for weekends. The experts tend to agree on that.

But despite several studies over the years, theories abound on why some months consistently have more births than others.