There really are more twins and triplets in Minnesota

Nearly every time I'm out and about, I see at least one mom or dad pushing a double stroller occupied by twins.

Maybe I notice them more because I was quite recently one of those moms pushing twins in a stroller, and I'm also a twin myself. But data show that it's not just my heightened awareness of twins. The rate of multiple births – twins, triplets, quadruplets and other higher-order multiples –nearly doubled in the past three decades.

Data on Minnesota births show that about 1 out of every 29 babies born last year was part of a set, up from 1 out of 55 in 1980, the earliest year available from the Minnesota Department of Health. (Note that the data count babies, not the number of pregnancies.) That's about 2,400 babies who were multiples, out of the nearly 70,000 who were born last year.

The multiples rate rose steadily through the 1990s and 2000s, peaking just as the recession took hold. It fell slightly and has remained fairly constant since then.

U.S. data from the National Center for Health Statistics show the multiple birth rate had been stable, at about 2 percent of all births (or 1 out of 50), from the time they started keeping data in 1915 through the 1970s. The most recently reported national rate is the same as Minnesota, at 3.5 percent.

My twin brother and I were born in the 1970s, that last decade before the rates started to rise. I distinctly remember people calling us "the twins" and strangers gawking at us on a regular basis. It was obvious that we were considered a rarity.

I thought it would be different with my boy-girl twins, who were born at the tail end of 2008. Multiple births were all over the news at the time. Numerous celebrities, including Angelina Jolie and Jennifer Lopez, had just given birth to twins. And then just a few weeks after mine were born, "Octomom" – Natalie Suleman – gave birth to octuplets in California.

That last question – are they natural? – gets at one of the two key reasons there are more twins, triplets and other multiple-birth babies in the world these days. The National Center for Health Statistics estimates that about two-thirds of the increase in twin births since the 1980s is due to fertility treatments, which can range from hormone therapy to expensive in vitro fertilization (IVF).

The increase is also due to more women waiting until they are older to have children, including me. Last year more than 2,000 babies were born to women age 40 and older in Minnesota (about 6 percent were multiples), up from about 800 in 1990 (about 4 percent were multiples).

Older women are naturally more likely to have a multiple pregnancy, plus they are more likely to use fertility treatments. Women age 35 and older are considered of "advanced maternal age," the slightly terrifying term my doctor used to describe me.

Last year in Minnesota, 12 percent of all babies born to women age 45 and older were multiple births. The rates are significantly lower among younger age groups, but you can see how it tracks upward with age.

Twins make up, by far, the greatest share of multiple birth babies. Last year, triplets and other higher-order multiples made up just 2 percent of all multiple births. That's down, though, from the late 1990s and early 2000s, which experts say is due to improvements in artificial reproductive technology.

In the meantime, I'll wish best of luck to anyone joining the multiple birth parents' club, including Pharrell Williams and his wife, who had triplets last month, Beyoncé and Jay Z., and George and Amal Clooney, who are both expecting twins later this year. It's not really as hard as it sounds.

Now that my twins are 8 years old and one is taller than the other, the "are they twins?" question almost never occurs. I look back at that really tough first year and try to forget the lack of sleep and never-ending feedings.

I still get the "you-must-be-exhausted" comments on a regular basis, though. (The answer: I'm no more exhausted than any other mom of two kids). One of my favorite comments, though, is when my friends tell me I did a good job bringing one of my most well-known skills to parenting: efficiency.