Twin FAQ

The two main types of twins are identical twins and fraternal twins. Identical twins form when one fertilized egg splits into two embryos. Fraternal twins form when two separate eggs are fertilized by two separate sperm cells.

A major global study estimated that the global twinning rate reached about 12 twin deliveries per 1,000 deliveries, with around 1.6 million twin pairs born worldwide each year.

Yes. Global research found that the twinning rate increased by about one third from the 1980s to the 2010s.

Yes. Twins can be born on different days if one baby is delivered before midnight and the other after midnight, or if there is a longer interval between deliveries.

Yes, although it is uncommon. If twins are born around midnight on New Year's Eve, one twin may be born in one calendar year and the other in the next.

Identical twins, also called monozygotic twins, form when one fertilized egg splits early in development and creates two embryos.

Fraternal twins, also called dizygotic twins, form when two separate eggs are fertilized by two separate sperm cells during the same pregnancy.

Fraternal twins are genetically similar to ordinary siblings because they come from two different eggs and two different sperm cells. They simply share the same pregnancy.

Identical twins share very similar DNA, but they are not the same person. Environment, lifestyle, development and epigenetic differences can influence how twins change over time.

No. Identical twins do not have identical fingerprints. Fingerprints are influenced by developmental factors in the womb, not only DNA.

Fraternal twinning is more likely to run in families because it can be linked to hyperovulation. Identical twinning is usually considered more random and is not strongly linked to family history in most cases.

The idea that twins always skip a generation is too simplistic. Family history can influence the chance of fraternal twins, but inheritance patterns are not as simple as a guaranteed generational skip.

Yes. Identical twins can differ in personality, health, interests, habits and life outcomes because development is shaped by both biology and environment.

Twin pregnancy is usually confirmed by prenatal ultrasound, which can show whether there are two fetuses.

Twin pregnancy symptoms can be similar to singleton pregnancy symptoms, but some people experience stronger nausea, fatigue or faster physical changes. Symptoms alone cannot confirm twins. This answer is general information only and not medical advice.

Twin pregnancies can be healthy, but they carry higher risks than singleton pregnancies and usually require closer monitoring. Risks include preterm birth, low birthweight and complications such as anaemia or pre-eclampsia. This answer is general information only and not medical advice.

Twins are more likely to be born before 37 weeks than single babies. NHS guidance reports that around 6 in 10 twins are born before 37 weeks. This answer is general information only and not medical advice.

Chorionicity describes whether twins have separate placentas or share a placenta. It is important because it affects monitoring and risk level during pregnancy.

Twin-to-twin transfusion syndrome, or TTTS, is a condition that can affect twins who share a placenta. It happens when blood flow between the twins becomes unbalanced. This answer is general information only and not medical advice.

Yes. Breastfeeding twins is possible, and many twins are breastfed until they start eating solid foods. Parents may feed both babies together or one at a time.

Yes. Twins can be formula fed, breastfed or combination fed. With formula feeding, bottles need to be prepared safely and freshly for each feed, which can take extra time with twins.

Many families find routines helpful, especially for feeding and sleep, but every family and every baby is different. The best routine is one that supports both babies and the parents.

Follow safe sleep guidance from qualified health authorities. The American Academy of Pediatrics recommends that babies sleep on their backs, in their own sleep space, on a firm flat mattress, without pillows, blankets, toys, bumpers or other soft items. This answer is general information only and not medical advice.

Parents can support individuality by using each child's name, spending one-on-one time with each twin, encouraging separate interests, respecting personal space and avoiding constant comparisons.

Yes. Twins are two individual children and may reach feeding, sleep, language, social or developmental milestones at different times. If parents are concerned, they should speak with a qualified healthcare professional.

Many twins describe a strong emotional bond because they share early life experiences and often grow up very close. The bond can be powerful, but every twin relationship is different.

No. Twin telepathy is a popular idea, but it is not scientifically proven. Similar reactions between twins are more often explained by shared genetics, shared environments, close familiarity and emotional connection.

Yes. Even identical twins can have different health outcomes because lifestyle, environment, stress, sleep, nutrition and individual experiences all matter.

Twins are useful in research because they help scientists understand how genetics and environment work together in health, behaviour, personality and development.