Increase Your Chance of Having Twins

For some parents, the idea of having twins is exciting. For others, it's scary. Either way, once a double bundle of joy arrives, new parents will be too happy and busy (and exhausted) to look back on how they felt before their babies were born.

Twins occur when one fertilized egg separates into two embryos, creating monozygotic, or identical twins, or when two eggs are fertilized by different sperm, which results in dizygotic, or fraternal twins.

While there is no real way to know ahead of time if either of these events will take place during conception, if you're pregnant or planning to become pregnant, here are some factors that may increase the odds you'll find yourself eating for three.


Your Genes

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Genetics play a big role in determining whether you'll have twins or not. Research published in 2007 suggests that a woman's chance of having twins is double if her mother or sister had twins.

Interestingly enough, the genetic factor only applies to fraternal twins. Among families with a history of twins, there are few with identical twins.

What this suggests is that genetics somehow play a role in multiple ovulation (also known as hyperovulation), in which more than one egg is released during a menstrual cycle.


Your Height or Weight

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A 2010 study published in the journal Fertility and Sterility found that mothers with a high BMI (body mass index) were significantly more likely to have fraternal twins than women of normal weight.

In women with a BMI over 30 (the clinical definition of obesity), the incidence of fraternal (but not identical) twins increased by 30% to 60%. Height also is a factor: Tall women, who fall in the top 25th percentile, are more likely to have twins than their more petite peers.

However, it's not a good idea to gain weight to increase your odds of having twins. There is no guarantee, and having a higher BMI increases your risk of miscarriage and gestational diabetes.

Body Mass Index (BMI) is a dated, biased measure that doesn’t account for several factors, such as body composition, ethnicity, race, gender, and age.

Despite being a flawed measure, BMI is widely used today in the medical community because it is an inexpensive and quick method for analyzing potential health status and outcomes.


Your Age

Older mother
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Numerous studies have shown that women 35 years and older are more likely to conceive fraternal twins than their younger counterparts. It is thought the genetic changes that occur with aging can accelerate and alter ovulation.

According to the American College of Obstetricians and Gynecologists, women of "advanced maternal age" are more likely to release more than one egg during ovulation.

It's important to note that being pregnant as an "older" woman poses some risks including miscarriage, gestational diabetes, and chromosomal abnormalities like Down syndrome.


Having Had Twins Already

Roger Federer two sets of twins
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Once you've had one multiple pregnancy, you're significantly more likely to have twins again

Again, this phenomenon appears linked to genetics and applies only to fraternal twins. A rare exception involves tennis star Roger Federer and his wife Mirka, who have two sets of identical twins (pictured).


A Diet Rich in Yams

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The Yoruba tribe in Nigeria has the highest rate of twin births in the world. Researchers in 2008 linked this phenomenon, in part, to a diet rich in cassava (a type of yam). The peel of this vegetable is thought to contain a compound (phytoestrogen) that may promote hyperovulation.

Scientists looking at the incidence of twins among the Yoruba believe genetics also may play a role. It appears that the propensity for twinning remains high among women who remain in the tribe as opposed to those have moved elsewhere and had children with non-Yoruban men.


Infertility Treatment

Woman holding bottle of clomid pills in hand
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Reproductive technologies have dramatically increased the rate of multiple births in the United States. For instance, the fertility drug Clomid (clomiphene) works by stimulating ovulation and sometimes cause the release of multiple eggs in a single cycle (referred to as superovulation).

On average, the rate of twinning in this country is around 3% overall. In people who take Clomid, that can increase by anywhere from 6% to 11.7%. Multiple births are even more likely to result from in vitro fertilization (IVF). In this case, it is not just that multiple embryos may be transferred; a single transferred embryo can sometimes divide and lead to monozygotic twins.


Going Off the Pill

Woman holding birth control pills
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It has long been suggested that stopping your birth control pills may cause overstimulation of the ovaries and lead to hyperovulation. It is believed that the sudden termination of the Pill may cause a spike in the production of follicle stimulating hormone (FSH) central to ovulation.

When this happens, the body may over-respond and release multiple eggs at once. Most studies suggest that the effect is only temporary and will normalize in a relatively short period of time.

According to the 2007 review, studies have conflicted over the years, with some reporting statistically significant increases in fraternal twins and others showing no association at all. Still, if you'd prefer not to have twins, use an alternate form of birth control for a few cycles after you stop taking the Pill. 


Pure Luck

Mom with twin babies
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Many parents of multiples don't meet any of the criteria for twinning, yet find themselves with two babies without even trying. Monozygotic twins are particularly surprising since no one is quite sure what can cause an egg to split after conception. It remains a mystery.

Want to try to have twins? There's no sure-fire way to improve your odds, and even if there were, keep in mind that the risks and complications associated with a multiple pregnancy can be significant. These include preterm birth, low birth weight, preeclampsia, and miscarriage.

7 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Hoekstra C, Zhao ZZ, Lambalk CB, et al. Dizygotic twinningHuman Reproduction Update. 2007;14(1):37-47. doi:10.1093/humupd/dmm036.

  2. Hoekstra C, Willemsen G, van Beijsterveldt CEMT, Lambalk CB, Montgomery GW, Boomsma DI. Body composition, smoking, and spontaneous dizygotic twinning. Fertil Steril. 2010;93(3):885-93. doi:10.1016/j.fertnstert.2008.10.012

  3. American College of Obstetricians and Gynecologists. Multiple pregnancy.

  4. March of Dimes. Being pregnant with twins, triplets and other multiples.

  5. Akinboro A, Azeez MA, Bakare AA. Frequency of twinning in southwest NigeriaIndian J Hum Genet. 2008;14(2):41–47. doi:10.4103/0971-6866.44104

  6. Schram CA. Outdated approach to a common problemCan Fam Physician. 2016;62(9):713–716.

  7. Centers for Disease Control and Prevention. ART and multiple births. Key findings: Fertility treatments and multiple births.

By Pamela Prindle Fierro
 Pamela Prindle Fierro is the author of several parenting books and the mother of twin girls.