Wondering if you might have two or more passengers aboard your mothership? Multiple births are, in fact, multiplying at a fantastic rate these days: The number of twin births has jumped more than 75 percent in the past 30 years; now, stats show that the there are about 33 twins born per every 1,000 births.
What’s behind this multiple-baby boom? The surge in older moms has a lot to do with it, along with an increase in fertility treatments and the rise in obesity, say experts. Yet these are only a few of the factors behind twin births.
With these incredible stats in mind, it’s not such a stretch to wonder if you might conceive more babies than you bargained for. Here are the overall odds of having twins, along with factors that could increase your chances.
What are the chances of having twins?
Nearly 4 percent of babies in the United States are now born in sets of two, three or more, with the majority — about 95 percent — of these multiple births being twins.
8 factors that increase the odds of having twins
A number of factors are at play when it comes to your chances of having fraternal twins. (Note that identical twins are rare and occur at random, so they’re even more of an exciting surprise!) Your chances of seeing double (or more) go up if:
- You have twins in your family. Heredity doubles your chances of conceiving twins — but only on the mom’s side. Even if your partner’s family tree is loaded with dynamic duos, that won’t increase your own odds of conceiving twins.
- You’ve had twins before. Lightning can and does strike twice! If you’ve already given birth to a set of twins, look out — you’re significantly more likely to do so again.
- You’re an older mom-to-be. As you age, your chance of conceiving twins increases. Researchers have found that women over 35 produce more follicle stimulating hormone (FSH) than younger women, which may cause more than one egg to drop at ovulation.
- You’ve been pregnant before. With each pregnancy, the odds that you’ll have twins go up a little, likely because with each pregnancy you’re a little bit older (which in itself ups the chances of having twins).
- You’re undergoing (or underwent) fertility treatments. Although fertility treatments don’t come with as high a multiple rate as they used to, having any kind of assisted reproduction (especially the kind that stimulates ovulation) multiplies the chances of a multiple pregnancy. About one-third of twin births and three-fourths of triplet births (and quadruplet births, etc) can be attributed to fertility treatments, according to a study in the New England Journal of Medicine.
- You’re overweight. Women with pre-pregnancy BMIs higher than 30 are significantly more likely to have fraternal twins than women with lower BMIs. Researchers hypothesize it’s because taller women have higher levels of insulin-like growth factor (IGF), which boosts ovulation by upping the sensitivity of the ovaries to FSH.
- You’re tall. Twins are more common in large and tall women than in small women (in an often-cited study, women who gave birth to twins were on average more than an inch taller than the average female, or 5 feet 5 inches vs. 5 feet 3 ¾ inches). Experts say it’s likely again because taller women have higher levels of IGF.
- You’re African-American. Black women are slightly more likely than Caucasians to have twins. If you’re Asian or Hispanic, however, you’re a bit less likely than Caucasians to get two-for-one.
Does having multiple factors mean I’m more likely to have multiples?
It’s true! If you can check more than one of the above boxes, your odds do increase slightly.