As far as we know, identical twins are completely random! Most of the time, the cause of identical twins is unknown. There are some genes that predispose women to hyperovulation releasing multiple eggs.
The genes for hyperovulation can be inherited! Age Older women generally have a higher chance of conceiving twins. A 35 year old woman is about 4 times more likely to have fraternal twins than a 15 year old! That is because they are experiencing some hormonal changes as they near menopause. This could encourage their body to release more than one egg during ovulation. Height Taller women are slightly more likely to have twins.
Researchers think that this might be related to having a higher quantity of a certain protein. This protein is released in response to growth factor and makes the ovaries more sensitive to follicle stimulating hormone.
Weight Women who are overweight also seem to have a higher chance of conceiving twins, especially if their BMI body mass index is above Diet This may sound crazy, but it looks like diet can also have an impact on your chance of having twins.
A study showed that diets that include animal products, particularly dairy, enhance the odds of a multiple pregnancy. This seems to be due to more growth hormone, increasing the concentration of a certain protein that stimulates ovulation. Ancestry If you meet 30 people of European ancestry, one of them is likely to have a twin brother or sister. On the other hand, you have the lowest chance of meeting a twin in Asia, where 1 in 70 people is a member of a twin pair.
And you have the highest chance to meet a twin in Nigeria, where 1 in 12 people has a twin sister or brother! Previous birth Your chance of having twins also increases if you have had a child before! Donna Krasnewich, M. Featured Content. Introduction to Genomics. Sometimes the blood supply is shared unequally, which can cause health problems for both twins. Women who are pregnant with twins sharing a placenta need to be checked more often than women with twins with separate placentas.
Frequent checks can pick up early on any potential complications. Twins sharing an inner sac monoamniotic are also at a higher risk of complications during pregnancy because of the chance that their umbilical cords might tangle and cut off their blood supply. These twins are checked even more closely.
Medical professionals often recommend that these twins are born earlier than other types of twins. Medical professionals use ultrasound to work out how many placentas twins have. The earlier the ultrasound, the more accurately it can say how many placentas there are.
It gets harder to work out later in pregnancy. After the birth, the placentas should be looked at to confirm or determine what type of twins they are. Same-sex twins with separate placentas can be fraternal or identical. To find out whether twins are identical or fraternal, you can ask for a genetic test after your babies are born. This is called a zygosity test. Identical twins are more likely than fraternal twins to get the same illness.
Research suggests that most cases of MZ twinning are not caused by genetic factors. However, a few families with a larger-than-expected number of MZ twins have been reported, which indicates that genetics may play a role. It is possible that genes involved in sticking cells together cell adhesion may contribute to MZ twinning, although this hypothesis has not been confirmed.
Most of the time, the cause of MZ twinning is unknown. Dizygotic DZ twins, also called fraternal twins, occur when two egg cells are each fertilized by a different sperm cell in the same menstrual cycle.
DZ twins are about twice as common as MZ twins, and they are much more likely to run in families. Compared with the general population, women with a mother or sister who have had DZ twins are about twice as likely to have DZ twins themselves. DZ twinning is thought to be a result of hyperovulation, which is the release of more than one egg in a single menstrual cycle. To explain how DZ twinning can run in families, researchers have looked for genetic factors that increase the chance of hyperovulation.
However, studies examining the contributions of specific genes have had mixed and conflicting results. Few specific genes in humans have been definitively linked with hyperovulation or an increased probability of DZ twinning.
Assisted reproductive technologies such as in vitro fertilization IVF are also associated with an increased frequency of DZ twins.
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