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Lots Of Parents Don’t Want Their Kids To Be Born On Leap Day

As soon as Noel Ziegler learned in July 2007 that she was pregnant with a March 5 due date, she realized she might give birth on leap day — Feb. 29, 2008 — and dreaded it. “I was 100 percent against it,” she said. She first went into labor on Feb. 25, but her doctor told her she wasn’t ready — it was too early. “At the stroke of midnight on the 29th, I went into labor” again, she said. “There was no stopping him.”

But her son, Thomas, who will turn 8 today (or is it 2?), likes his birthday. He told me by phone from the Ziegler home in a Philadelphia suburb, “I’m like, ‘Mom, I get to live my life over again!’ ” because he got to celebrate his second birthday in 2010, and is doing so again this year. “I’m actually glad things panned out the way that they did,” his mother said. “We wouldn’t change it for the world.”

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Still, Ziegler was far from alone in not wanting to give birth on leap day. Modern parents can often choose their children’s birthdates just as they can choose their names, and many choose to avoid Feb. 29. As a result, a leap day birthday is even rarer than we’d expect.

Feb. 29 comes around once every four years,1 an add-on to make calendar math add up. So you’d think there would be about a quarter the number of leap day babies — also known as leaplings, leapers or leap year day babies — as there are people born on any other day.

But in fact, there are 7 percent fewer than you’d expect. The chief reason appears to be that there are far fewer cesarean deliveries on Feb. 29 than on surrounding days. Leap day babies, their mothers and their obstetricians say many mothers try to avoid delivering on the quadrennial date by scheduling induced labor or cesareans on a different date.

“Who wants a birthday that comes every four years?” Neel Shah, assistant professor of obstetrics and gynecology at Harvard Medical School, said in a telephone interview.

Tristen Ross remembers knowing a leap day baby when she was young and thinking, “Oh man, you only get a birthday once in four years. That sucks!” She wanted to avoid Feb. 29 when, in June 2011, she found out she was pregnant, though her husband, Joe Ross, was gung-ho. Her due date was Feb. 22 — but not until six days later, near the end of an evening of “Star Wars” marathon viewing in their Boston home, did she go into labor. “This baby was coming on the 29th whether we liked it or not,” Joe said.

Jacoby Leap Day Tattoo.jpg

Now the Rosses say they love that their son is a leap day baby. Shortly after Jacoby was born, Joe got a tattoo of a leaping frog on his right bicep. They’ve bought two of the several books available for parents of leap day babies — truly a niche market.

Having to wait four years between birthdays is just one potential frustration for leap day babies. In interviews with some of them and their parents, most of whom I found via a posting on a Facebook group many inhabit, they described being teased by classmates, trying to avoid being asked when their birthday is, and encountering suspicions from bouncers, doctors and government agencies about the birthdates on their ID cards.

Even those leap day babies who’ve experienced occasional hassles say they’re glad to be part of the exclusive club. But remember, these are people who are excited enough about their birthday to join a Facebook group. Many people were born on adjacent days in leap years because their parents wanted to avoid it. Scott Sullivan, director of maternal-fetal medicine at the Medical University of South Carolina in Charleston, said a normal Monday would have three or four deliveries scheduled in his hospital. Just two were scheduled for today.

National birth data for the last four leap days bears this out. Even though cesarean deliveries make up only about one-third of all births — and not all of them are scheduled — they account for two-thirds of the missing leap-day births.

The National Center for Health Statistics sent us daily birth counts between Feb. 22 and March 7 for each of the last four leap years — 2000, 2004, 2008 and 2012 — broken down by vaginal and cesarean deliveries. Comparing Feb. 29 to Feb. 22 and March 7 — that is, one week earlier and one week later — should control for any seasonal and day-of-week variation.

Vaginal births were on average 3 percent lower on leap day than a week before or after, cesarean births were 15 percent lower, and overall births were 7 percent lower. On average, about 850 babies you’d expect to be born on Feb. 29 weren’t.2

bialik-leapbabies-2

These numbers are based on just four leap days.3 Yet for data this sparse, the evidence is compelling.

Take, for instance, the one leap day in the data set that fell on a weekend: Feb. 29, 2004, a Sunday. It would make sense if there were less of an effect that year, since few deliveries are scheduled on Sundays, whether they are leap days or not. And that Feb. 29 does, indeed, show the smallest drop-off in births of the four we looked at.4 If today is more like other weekday Feb. 29s, then the overall drop in births will be more like 9 percent than 7 percent. (Though since the last leap day, medical opinion has turned against many elective inductions of pregnancy.)

We checked every other possible comparison in our data set between Feb. 29 and adjacent days, and all confirmed the leap-day-baby gap. The increase to March 1 is especially pronounced, as you’d expect if some deliveries were delayed a day. And we couldn’t find evidence that a rash of Feb. 29 blizzards were delaying the deliveries — if anything, there’s been less snow on leap day than on the days around it.

Also, there’s plenty of evidence that modern medicine can schedule babies’ arrival. In 2013, the average number of births on a weekday was more than 50 percent greater than the average on a weekend day, according to NCHS. Cesarean deliveries were more than twice as common on the average weekday as on the average Saturday or Sunday, because hospitals try to schedule them on days when they are fully staffed.

bialik-leapbabies-1

Leap day babies really are special, even more than the day they were born, which comes around just once every 1,461 days. And they will celebrate their birthdays on Monday as few people ever get to do.

“When that fourth year comes around, I write my birthday on the calendar so that it covers every inch of that box with a ‘29′ in it,” said Leann Silva, who turns 20 (or 5?) today. She plans to join her classmates at the University of Nevada, Reno, in a campus leap-day event consisting of, well, leaping. “If nothing else, I will be enjoying the fresh air outside and cherishing the day I’ve spent the last four years waiting for,” Silva said. “I wouldn’t want to be born on any other day.”

Footnotes

  1. Except in years that are divisible by 100, but not by 400 — but the last one of those exception years came in 1900, and the next is in 2100, so a vast majority of people alive today will never need to know the exceptions. ^
  2. The Social Security Administration sent us its own data for the same days, which also suggested a 7 percent drop in leap day births compared to a week before and after. ^
  3. An NCHS spokesman said it would take weeks to get data from previous leap days, which isn’t stored in a convenient format. ^
  4. Vaginal births fell by 1 percent, cesareans by 5 percent and all births by 1 percent. ^

Carl Bialik is FiveThirtyEight’s lead writer for news.

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