Twins (2024)

FAQs

Twins? ›

Multiple births are more common than they were in the past, due to the advancing average age of mothers and the associated rise in assisted reproductive techniques, in particular the use of fertility drugs. There are two types of twins – identical (monozygotic) and fraternal (dizygotic).

Multiple births are more common than they were in the past, due to the advancing average age of mothers and the associated rise in assisted reproductive techniques, in particular the use of fertility drugs. There are two types of twins – identical (monozygotic) and fraternal (dizygotic).

The likelihood of conceiving twins is a complex trait, meaning that it is affected by multiple genetic and environmental factors, depending on the type of twins. The two types of twins are classified as monozygotic and dizygotic.

Increase the chances of getting pregnant with twins by getting pregnant in your 30s or later; finding a partner with a family history of twins; increasing your weight; breastfeeding regularly; consuming dairy products; and getting pregnant repeatedly.

Traditionally, the science around twins has taught that identical and fraternal are the only two types. But a third type might exist, called polar body or half-identical twins.

The simple answer is yes. While there have been a few reported cases of identical twins being born with different sexes, this occurrence is so rare, it's not something twin parents should realistically consider as a possibility.

In rare cases, fraternal twins can be born from two different fathers in a phenomenon called heteropaternal superfecundation. Although uncommon, rare cases have been documented where a woman is pregnant by two different men at the same time.

The notion that twins always skip a generation is also a myth. The illusion may have arisen because men who inherit the gene from their mothers are unaffected by it ( they do not ovulate), but can still pass it on to their daughters, who, in turn, will have an increased likelihood of conceiving twins.

Everyone has the same chance of having identical twins: about 1 in 250. Identical twins do not run in families. But there are some factors that make having non-identical twins more likely: non-identical twins are more common in some ethnic groups, with the highest rate among Nigerians and the lowest among Japanese.

It's a misconception that twins have identical fingerprints. While identical twins share many physical characteristics, each person still has their own unique fingerprint. If you're curious about how identical twins are similar and how shared fingerprints aren't possible, read on to learn more.

In what month are most twins born? ›

Rate of twin births in the U.S. in 2020 and 2021, by month

In 2021, the month with the highest rate of twin births in the United States was July with almost 33 twin births per 1,000 total births. This statistic shows the rate of twin births in the United States in 2020 and 2021, by month.

Older age– Women over 30 have a greater chance of multiple conception. Many women today are delaying childbearing until later in life, and may have twins as a result. High parity – Having one or more previous pregnancies, especially a multiple pregnancy, increases the chances of having multiples.

About 1 in 3 of all sets of twin births are vagin*l births. You may choose to have an elective caesarean, or your doctor may recommend a caesarean section because of potential complications. Even if you plan a vagin*l birth, you may end up having an emergency caesarean section due to complications during labour.

Monoamniotic-monochorionic Twins

This is the rarest type of twin, and it means a riskier pregnancy as the babies can get tangled in their own umbilical cords. If you have monoamniotic-monochorionic twins, your healthcare provider will monitor your pregnancy closely.

If twins are a boy and a girl, clearly they are fraternal twins, as they do not have the same DNA. A boy has XY chromosomes and a girl has XX chromosomes. Girl-boy twins occur when one X egg is fertilized with an X sperm, and a Y sperm fertilizes the other X egg.

Sex determination in twins occurs as normal, with males having XY and females having XX. The sex of a fetus, even twins, can be identified via an ultrasound at week 14-21 of the pregnancy. Twins can consist of males, females, or both, with female twins being the most common.

Because fraternal, or dizygotic, twins are 2 separate fertilized eggs, they usually develop 2 separate amniotic sacs, placentas, and supporting structures. Identical, or monozygotic, twins may or may not share the same amniotic sac, depending on how early the single fertilized egg divides into 2.

Whether you are a twin yourself or a parent of twins, a DNA test can answer the question of whether multiple birth children are genetically identical or not. A zygosity test is performed by collecting a sample of cheek cell DNA from each sibling, using a cheek (buccal) swab.

About 23 in every 1000 births are fraternal, a much higher rate than the three or four out of 1000 births for identical twins. Examining each twin's DNA will reveal whether they are identical or fraternal; fraternals also normally have separate amniotic sacs, as well as separate placentas.

Although identical twins have the same genes, they don't always look the same. This is because children's health and development are shaped not only by genes but also by experiences in the womb and after birth. For example, a twin who gets less blood from a shared placenta might weigh less at birth.