What Are My Chances of Having Twins?

Odds of Conceiving Twins Naturally or With Fertility Treatment

identical twin baby boys (3-6 months) lying side by side, portrait, chance of having twins

Niki Mareschal/Photographer's Choice/Getty Images

What boosts your odds of having twins? Fertility treatments like Clomid, Gonal-F, and Follistim make it more likely you'll conceive multiples. But other factors like your height, age, and even family history can also increase your odds of birthing more than one baby. If you've always wanted multiples, here is some insight into how to have twins.

Causes of Twins Without Treatments

Fertility treatments are not the only cause for twins and higher order pregnancies. Here's an overview of the other factors that increase your chances of getting pregnant with multiples.

Age

People over 30 are more likely to conceive twins. This is because the hormone FSH rises as a woman gets older. FSH, or follicle-stimulating hormone, is responsible for the development of eggs in the ovaries before they are released.

As people age, they require higher levels of FSH because their eggs require more stimulation to grow than in a younger woman. This is somewhat ironic given that increased FSH occurs due to lowering fertility. Sometimes, the follicles overreact to higher FSH levels and two or more eggs are released, resulting in a multiple pregnancy.

Family History

A family history of identical twins does not necessarily make you more likely to have multiples, although the offspring of male identical twins may be more likely to have their own identical twins. However, if you have fraternal twins (non-identical) in your family, your chances of conceiving twins rise. If there are fraternal twins on both the mother and father's side, your odds for twins go up even higher.

A history of fraternal twins on the female side of the family indicates a higher likelihood of ovulating more than one egg per cycle.

Weight

People who are obese—with a BMI over 30—are more likely to conceive twins than people with a healthier BMI. Extra body fat leads to increased levels of estrogen, and higher levels of estrogen can lead to overstimulation of the ovaries. Instead of releasing just one egg at ovulation, the ovaries may release two or more. Ironically, other factors make it more difficult for some overweight people to conceive.

Height

People who are taller than average are more likely to have twins. One study found that people averaging 164.8 cm in height (about 5'4.8") were more likely to conceive twins than people averaging 161.8 cm (about 5'3.7"). Why this happens isn't clear, but one theory is that better nutrition (which may lead to more height) is partially behind the increased rate of twins.

Breastfeeding

People who conceive while breastfeeding are more likely to conceive twins than people who are not. It's true that breastfeeding can also suppress fertility and prevent pregnancy, specifically during a baby's first six months if the baby is exclusively breastfed. However, it is possible to get pregnant when breastfeeding—and with twins!

One study found the rate of twins to be 11.4% among breastfeeding people , as compared to just 1.1% in non-breastfeeding people .

Diet

While research is still ongoing, some studies have found that people who eat a lot of dairy products are more likely to conceive twins. One theory is that the growth hormones given to cows affect the hormone levels in humans.

Other Factors

Twins are more common in people who have carried many pregnancies and have large families. Meanwhile, Blacks also are more likely to conceive twins than white people. Asian people are the least likely to conceive twins.

Odds of Having Twins With Treatments

Fertility treatments that boost ovulation can lead to twins, triplets, or higher order multiples. Conceiving multiples is a potential risk of fertility treatments, and one that can possibly be reduced with careful monitoring, single embryo transfer (for IVF treatment), and the lowest possible effective dosage (when treating with gonadotropins).

You may wonder why conceiving multiples is considered a "risk" and not a potential benefit to fertility treatments. After all, if you've been struggling to get pregnant, wouldn't a double or triple blessing be a good thing? The fact is that multiple pregnancies come with risks to the parent and babies. Your doctor's goal is for you to conceive and give birth to one healthy baby at a time.

Overall Rate
  • Twins 3.21%

  • Identical twins 0.45%

  • Triplets and higher order multiples 0.1%

With Treatments
  • Identical twins 0.95%

  • Clomid and Femera: 5-12% twins, under 1% higher order multiples

  • Gonadotropins: up to 30% twins, up to 5% higher order multiples

  • IVF (under age 35): 12.1% twins

  • IVF (age 35-37) 9.1% twins

  • IVF (age 38-40): 5.3% twins

Not all treatments for infertility increase your odds of twins, but most do. Here are some of the treatments that may lead to twins.

Clomid and Femera have the lowest rate of twins, ranging from 5% to 12%. The rate of triplets and higher order multiples is under 1%. Gonadotropins, whether used with or without IUI treatment, have the highest rate of twins.

According to some studies, up to 30% of pregnancies conceived with gonadotropins lead to multiples. Most of these pregnancies are twin pregnancies, but up to 5% are triplet or higher order pregnancies.

Contrary to popular belief, IVF treatment is not the main source of triplet and higher order pregnancies. Data collected by the CDC indicates that the rate of IVF-conceived triplets in 2014 was 1.5% of pregnancies (but only 0.9% of live births, lower due to pregnancy loss).

IVF twins are relatively common, with the twin rate highest for people younger than 35, at 12.1% per transfer in 2014. The IVF twin rate is lower for people over age 35—9.1% for people aged 35 to 37 and 5.3 for people ages 38 to 40—likely due to the overall decreased success rate as a woman ages.

How Common Are Twins?

According to CDC birth statistics, there were 120,291 infants born in twin deliveries in the United States in 2019. That's 32.1 twins per 1,000 live births, or put another way, about 3.21% of live births. There were 3,136 triplet births and just 150 quadruplet and higher order births during the same year. These numbers include naturally occurring multiples, along with those conceived with fertility treatment.

The rate of multiple births increased and peaked during the 1990s but has been declining over the past decade. The percentage of triplet and higher order pregnancies has dropped 36% since 2004.

Chances of Having Identical Twins

In the general population, identical twin pregnancies occur 0.45% of the time, or 1 in 250 births. While most multiple pregnancies conceived with fertility treatments are fraternal twins, the use of fertility treatment increases your risk of having identical twins.

According to one study, identical twins made up 0.95% of the pregnancies conceived with treatment. That's double the general population's risk. It's unclear why fertility treatment leads to more identical twins.

One theory is that the culture embryos are placed in during IVF increases the risk of identical twinning. Another theory is that treatments using gonadotropins lead to the increased risk of identical twins.

Odds of Having Higher Order Multiples

Anyone trying to conceive will find their chances of having higher order multiples much lower than twins or single births. Without fertility treatments, the odds of conceiving triplets spontaneously is around 1 in 1,800. For quadruplets, the odds are estimated to be around 1 in 729,000.

With fertility treatments, the chances of a higher order pregnancy rise substantially. In 2019 for example, the rate for triplet and higher-order multiples was 87.7 per 100,000 births (0.877 per 1,000 births). Estimates are that just over three-quarters of triplets and higher-order multiples are the result of fertility treatments.

Frequently Asked Questions

What are the chances of having twins if they run in your family?

A family history of identical twins will not necessarily increase your chances of having them yourself, although the offspring of male identical twins is more likely to have them. However, you are more likely to have twins if there are fraternal twins in your family. If there are fraternal twins on both your mother's and father's sides of the family, your chances of having twins are even higher.

How can I increase my chance of having twins?

Some factors that increase your odds of having twins are out of your control, like your family history and height, for example. But there other ways to improve your odds if you're hoping for multiples. Factors that increase the chance of twins include: consuming high amounts of dairy foods and conceiving over the age of 30, and while breastfeeding. Many fertility drugs including Clomid, Gonal-F, and Follistim increase the odds of a twin pregnancy.

A Word From Verywell

Your chances of having twins will depend not just on your use of fertility drugs, but also your family history, race, age, and many other factors. These factors do work together. In other words, a tall person with a family history of fraternal twins is more likely to conceive twins during fertility treatments than a short woman without any family history of twins.

Your chances of conceiving twins will also be affected by your particular cause of infertility. A young woman with healthier eggs is more likely to conceive twins than a person over 40, whose egg quality is poor.

The twin and multiple rates also vary from fertility clinic to clinic. Twin rates differ based on how carefully they track ovulation stimulation during fertility drug use and how many embryos they transfer during IVF.

While having twins may sound like the kind of two-for-one deal any couple would love to have after infertility, it really is best to aim for one healthy baby. Your doctor can reduce the odds of multiples with careful monitoring and single-embryo transfer during IVF.

However, if you do conceive twins or more, know that good prenatal care can reduce your risk of complications. There are also many positive benefits to having twins.

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