Baby bump: Popular date for births
Published 9:02 pm, Thursday, June 26, 2014
It's about to be baby season in Danbury.
A team of researchers at the University of Michigan published a study in April, which explains the increase in women with baby bumps strolling down the streets this time of year is no coincidence. After obtaining birth records for babies born in all 50 states between 1931 and 2008, the scientists found trends that show mommies in the northeastern portion of the nation tend to deliver their children in June and July.
"In the pre-baby boom era, we had a pattern where in the northwest and the Northeast, they're occurring in June and July," said Kevin M. Bakker, a Ph.D. candidate at the university who co-authored the paper along with Micaela Martinez-Bakker. "As you move south, closer to the equator, they occurred later and later, into October and November, and then in the southeast, they had two different peaks in the spring and the summer."
When the baby boom rolled through, the peaks were harder to track, as babies were speeding up throughout the entire year. But from 1965 to 2008 the peaks began to redefine themselves, with Connecticut's continuing to come in the early summer.
An analysis of more than 5,500 birthdates recorded for current kindergartners in eight districts across southwestern Connecticut -- Danbury, Darien, Fairfield, Greenwich, New Canaan, Norwalk, Ridgefield and Stamford -- finds the most popular birthdate for this cohort of students -- many of whom were born in the last year the study examines -- was June 27.
"That's directly in line with that we found, because in the northern part of the country, you have those earlier birth peaks," Martinez-Bakker said. After some digging, her partner was able to find the most common birthdate across all of Connecticut in the 43-year span between 1965 and 2008 was July 20.
But the "million-dollar question" the researchers are still wondering about is whether the flood of newborns about to hit southwestern Connecticut is tied to conditions we see this time of year or about nine months ago.
"There are two main hypotheses here," Martinez-Bakker said. The first has to do with human behavior, and the fact that copulation may increase at given times, coinciding with holidays and other events, she said.
"The second is that essentially it's our human physiology that changes throughout the year and even though humans may be copulating throughout the year, there may be differences in fertility and in sperm motility," she said.
Think about it this way: Rodents, bears and other non-human animals have distinct times of year when they mate and reproduce.
But another researcher at the University of Notre Dame thinks there may be something about the timing that links up with a parent's social standing. In a paper published last July in The Review of Economics and Statistics, Kasey Buckles, an associate professor of economics at Notre Dame, studied the socio-economic differences of women who give birth in the winter, versus those who give birth in the summer months.
"What we found is that it looks like mothers generally have preferences for avoiding winter births, but high socio-economic status moms have those preferences more strongly," said Buckles, whose study examined more than 50 million birth certificates from the 1960s to the 2000s. "More highly educated women who are in the education field or in an office setting may prefer to not have babies in the school year or the traditionally busier seasons at work."
Nationwide, the relative peak -- the time when a baby is far more likely to be born to a high-income mother than one with a low income -- occurs in May.
"There are things that go on during the year that increase the number of conceptions -- like New Year's Eve -- but it seems to be that people are targeting birth at certain times of the year," she said.
Here in southwestern Connecticut the storks are fueling up for a long couple of weeks.
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