How Can We Have Twins?

Twins happen in one of two ways: either two separate eggs are released and fertilized, or a single fertilized egg splits into two embryos. The first type is called fraternal (dizygotic) twins, and the second is identical (monozygotic) twins. Fraternal twins run in families and become more likely with age and fertility treatment. Identical twins are largely a matter of chance and do not run in families in any meaningful way. There is no method, diet, or supplement proven to reliably produce twins on demand.

How Can We Have Twins? The Two Basic Mechanisms

Every twin pregnancy starts with one of two events, and understanding the difference explains almost everything else about twins.

Fraternal twins come from two eggs. During a normal menstrual cycle, one egg usually matures and is released. Sometimes two are released in the same cycle — a process called hyperovulation. If both are fertilized, two embryos develop. These twins are no more genetically similar than any two siblings. They can be two girls, two boys, or a girl and a boy.

Identical twins come from one egg. A single egg is fertilized by a single sperm, and at some point in the first days of development, the embryo splits into two. The two resulting embryos share nearly identical DNA. They are always the same sex. This split is not inherited and appears to occur at random. No one can predict or deliberately trigger it.

The distinction matters because the factors that raise your odds of twins mostly affect fraternal twinning. Identical twinning rates stay fairly steady across populations and time — roughly a few per 1,000 births worldwide — while fraternal rates vary widely depending on age, ancestry, and fertility treatment.

What Raises the Odds of Fraternal Twins?

Several well-documented factors increase the chance of releasing two eggs in one cycle.

• Family history on the mother’s side. A tendency to hyperovulate can be inherited. If the mother herself is a fraternal twin, or has fraternal twins among her close relatives, her odds rise. The father’s family history is largely irrelevant, because twinning depends on the mother releasing two eggs.
• Maternal age. Women in their mid-to-late 30s have higher rates of fraternal twinning than younger women, likely because shifting hormone levels can prompt the release of more than one egg. This effect declines again after about age 40.
• Ancestry. Fraternal twinning rates are highest in some populations of West and Central African descent and lowest in people of Asian descent. The reasons are not fully understood but appear to involve genetic and hormonal differences.
• Fertility treatment. This is the single largest driver of the rise in twin births over recent decades. Ovulation-stimulating drugs and transferring more than one embryo during in vitro fertilization both increase the chance of twins.
• Height and body type. Some research has linked greater maternal height and higher body mass index to slightly higher twinning rates. The effect is modest.

Notice what is not on this list: diet, supplements, or timing of intercourse. No reliable evidence shows that any food, vitamin, or sexual practice causes twins.

Can Fertility Treatment Increase the Chance of Twins?

Yes, and it is the most controllable factor — though it is a medical decision, not a lifestyle one.

Two main categories of treatment raise twin odds:

Ovulation induction. Medications that stimulate the ovaries can cause more than one egg to mature and release. This includes drugs like clomiphene citrate and injectable gonadotropins. The more eggs released, the higher the chance of multiples.

In vitro fertilization (IVF). When more than one embryo is transferred into the uterus, each has a chance of implanting. Transferring two embryos raises twin odds substantially compared with transferring one.

Because of the health risks of multiple pregnancies to both mother and babies, reproductive medicine has moved toward transferring fewer embryos. Many clinics now favor single embryo transfer in appropriate cases, especially for younger patients with a good prognosis. The goal is one healthy baby at a time. If you are considering fertility treatment and want to understand your specific odds, that conversation belongs with your fertility specialist, not a general article.

One clarification worth knowing: fertility treatment raises the rate of fraternal twins mainly through multiple eggs or multiple embryos. It does not appear to meaningfully raise the rate of identical twinning.

Do Identical Twins Run in Families?

No. Identical twinning is not inherited in any way researchers have been able to demonstrate.

The split of a single embryo appears to be a random developmental event. It occurs at a relatively constant rate around the world, regardless of family history, ethnicity, or age. If someone in your family has identical twins, that does not raise your own odds.

This is a common point of confusion. People often say “twins run in my family” without distinguishing which kind. If the twins in question are fraternal, there may be a real inherited tendency. If they are identical, the family connection is coincidental.

Are There Natural Ways to Increase Twin Chances?

No proven natural method exists to make twins more likely.

Online claims about certain foods — yams, dairy, cassava — raising twin odds circulate widely, largely because some populations with high twinning rates also eat these foods. That is a correlation, not proof of cause. The high twinning rates in those populations are better explained by genetics. No controlled study has shown that eating any specific food causes twins.

Similarly, there is no supplement, herbal product, or timing strategy with reliable evidence behind it. Some sources suggest folic acid or other factors, but the evidence does not support these as twin-inducing.

If you genuinely want to pursue a higher chance of twins, the only factor with real, controllable impact is fertility treatment — and that carries real risks, which a doctor should walk you through.

What Are the Risks of a Twin Pregnancy?

Twin pregnancy is not simply “two of everything.” It carries higher risks than a singleton pregnancy, for both the mother and the babies.

For the mother, risks include higher rates of:

• Gestational diabetes
• High blood pressure and preeclampsia
• Preterm labor and delivery
• Cesarean delivery
• Postpartum hemorrhage

For the babies, the main concerns are preterm birth and low birth weight, since twins often arrive early and are smaller than singletons. Preterm birth is the leading cause of complications in twins. Twins are also more likely to need care in a neonatal intensive care unit.

Identical twins share additional risks depending on when the embryo split. If the split happens later — after the point when the membranes form — the twins may share a placenta or amniotic sac, which can create complications like twin-to-twin transfusion syndrome. These situations require closer monitoring.

This is why many clinicians counsel against deliberately aiming for twins. The goal of fertility treatment is a healthy baby, and a single pregnancy is generally the safest route to that outcome. Anyone weighing the idea of twins should understand that the medical picture is more complicated than it looks from the outside.

Can You Choose to Have Twins?

No. There is no reliable way to choose twins, and no medical treatment designed specifically to produce them.

Fertility treatment raises the odds as a side effect of how it works, not because it targets twins. In fact, modern practice increasingly aims to reduce twin pregnancies, not create them. A clinic that deliberately transfers multiple embryos solely to get twins would be acting against current medical guidance.

If you are hoping for twins, the honest position is this: fraternal twinning can be influenced by factors like age, family history, and fertility treatment, but none of these can be dialed up with certainty. Identical twinning cannot be influenced at all. For most people, whether they have twins comes down to chance.