Your chances of having twins depend on a mix of genetics, body composition, diet, and reproductive choices. The baseline rate of twinning in the general population is relatively low, but several factors can shift those odds meaningfully. Some are things you’re born with, others involve lifestyle choices, and the most dramatic increases come through fertility treatments.
It’s worth noting upfront that most of these factors apply to fraternal (dizygotic) twins, which form when two separate eggs are released and fertilized in the same cycle. Identical twins, where a single fertilized egg splits, appear to happen mostly at random and aren’t well understood genetically.
Family History and Genetics
If fraternal twins run in your family, particularly on the maternal side, your odds roughly double. Women who have a close relative like a sister who gave birth to fraternal twins are about twice as likely to have twins themselves compared to the general population. This is because the tendency to release more than one egg during ovulation (called hyperovulation) can be inherited. Your partner’s family history of twins doesn’t directly affect your chances, since the key factor is whether your body releases multiple eggs.
That said, scientists haven’t pinpointed many specific genes responsible for hyperovulation in humans. The genetic link is real but complex, likely involving multiple genes with small individual effects rather than a single “twin gene.”
Body Size and Age
Women with a higher BMI have higher levels of a growth factor called IGF, which plays a role in ovarian stimulation. Taller women also tend to have elevated IGF levels. Both traits are associated with a greater chance of releasing multiple eggs. This doesn’t mean gaining weight is a recommended strategy, but it helps explain why twinning rates vary across populations and body types.
Age is another significant factor. Women over 35 are more likely to conceive twins naturally. As you get older, your body produces more follicle-stimulating hormone to compensate for declining fertility, and higher levels of this hormone can trigger the release of two eggs in a single cycle. It’s one of those biological ironies: fertility decreases with age, but the odds of twins actually go up.
Diet and Dairy Consumption
What you eat may influence your twinning odds more than you’d expect. A study published in The Journal of Reproductive Medicine found that vegan women, who consume no animal products, have a twinning rate just one-fifth that of vegetarians and omnivores. The proposed mechanism is IGF levels, which rise proportionally with dairy intake. Milk consumption in particular appears to boost circulating IGF, which can stimulate the ovaries to release more than one egg.
The effect may be even more pronounced in countries where dairy cattle receive growth hormone, since those products contain higher IGF levels. If you’re actively trying to conceive twins, incorporating dairy into your diet is one of the simpler lifestyle adjustments supported by research. Conversely, avoiding all animal products appears to significantly lower the probability.
Conceiving While Breastfeeding
One of the most striking natural factors: women who become pregnant while still breastfeeding are nine times more likely to conceive twins than women who are not breastfeeding at the time of conception. This finding comes from research by Dr. Gary Steinman, who has studied twinning mechanisms extensively. The hormonal environment during breastfeeding, particularly fluctuations in IGF, appears to increase the likelihood of releasing multiple eggs when ovulation resumes.
This only applies if you already have at least one child, obviously, and getting pregnant while breastfeeding can be difficult since breastfeeding often suppresses ovulation. But for women who do conceive during this window, the odds of twins jump considerably.
Fertility Medications
The most reliable way to increase your chances of twins is through fertility treatments, though these are designed to treat infertility rather than produce multiples. Ovulation-stimulating medications work by encouraging the ovaries to release more than one egg per cycle.
Clomiphene citrate, one of the most commonly prescribed fertility drugs, carries a multiple pregnancy rate of about 9.4%. A newer alternative produces multiples at a lower rate of roughly 4.8%, while achieving similar overall pregnancy rates. These medications are prescribed by reproductive specialists and require monitoring, since the goal is typically a healthy singleton pregnancy. But the increased twin rate is a well-known side effect.
IVF and Embryo Transfer
In vitro fertilization historically produced high rates of twins and higher-order multiples because doctors routinely transferred two or more embryos. That practice has shifted dramatically. In the UK, for example, the multiple birth rate from IVF has dropped to an all-time low of about 6%, or roughly 1 in 20 IVF births. This happened because clinics moved toward transferring a single embryo and freezing the rest, a strategy that maintains the same overall success rate while reducing the risks associated with multiples.
If two embryos are transferred, the chance of twins rises substantially. But most fertility clinics now discourage this for younger patients with good prognoses, because twin pregnancies carry higher risks for both mother and babies. Some patients do request or receive double embryo transfers, particularly older patients or those who have had previous failed cycles, and this remains the most direct path to a twin pregnancy.
What Doesn’t Work: Folic Acid
You may have seen claims that taking folic acid supplements increases twin rates. A large CDC-backed study of nearly 242,000 women found no such link. Women who took 400 micrograms of folic acid daily before conception and during early pregnancy had the same rate of twins (less than 1%) as women who took none. Folic acid is important for preventing neural tube defects, but it won’t affect your chances of having twins.
Risks Worth Knowing About
Before actively pursuing a twin pregnancy, it’s important to understand that carrying twins comes with meaningfully higher medical risks. Women pregnant with twins face increased rates of gestational hypertension, preeclampsia, and gestational diabetes compared to singleton pregnancies. Twin pregnancies also carry a significantly elevated risk of premature delivery, and premature infants face a wide range of potential health challenges.
These risks don’t mean twin pregnancies can’t go smoothly. Many do. But the gap in complication rates between twin and singleton pregnancies is large enough that fertility specialists actively work to minimize multiple pregnancies rather than encourage them. If you’re hoping for twins, going in with realistic expectations about the additional monitoring, physical demands, and potential complications will help you make an informed decision about how aggressively to pursue it.