How can twins be identical

In a very small number of identical twins, splitting might happen even later. In this case, both twins share an inner sac , called the amnion, in addition to sharing a placenta. The technical name for this is monoamniotic twins. For example, a twin who receives less blood from a shared placenta might weigh less at birth. Sharing a placenta means that twins share a blood supply during pregnancy. 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. Share this post:. Share on facebook Facebook. Share on twitter Twitter. Share on linkedin LinkedIn.

Share on email Email. Similar Post. Multiple Births. Multiples Pregnancy: Twins, Triplets and More A multiples pregnancy means having twins, triplets or multiples. After a menstrual period, rising levels of the hormone oestrogen help to thicken the lining of the womb the endometrium and release an egg from one of the ovaries ovulation.

If the egg is fertilised on its journey down the fallopian tube, it lodges in the thickened womb lining, starts dividing and evolves into an embryo.

This occurs because the fertilised egg divides in two while it is still a tiny collection of cells. The self-contained halves then develop into two babies, with exactly the same genetic information.

The biological mechanisms that prompt the single fertilised egg to split in two remain a mystery. Approximately one quarter of identical twins are mirror images of each other, which means the right side of one child matches the left side of their twin. These babies will be no more alike than siblings born at separate times.

The babies can be either the same sex or different sexes, with the odds roughly equal for each. It is proposed that the egg splits in two, and each half is then fertilised by a different sperm.

This theory is an attempt to explain why some fraternal twins look identical. Gestation for twins The normal length of gestation for a single baby is around 40 weeks. However, gestation for twins, either identical or fraternal, is usually around 38 weeks.

Since twins are usually premature, they are more likely to have lower birth weights. Prematurity is associated with increased risk of a number of disorders, including jaundice. Giving birth to twins Childbirth can give rise to complications when just one baby is present, so twins present extra potential for difficulties. It is advised that women carrying twins give birth in hospital, rather than at home.

The babies can be delivered vaginally, but caesarean section delivery may be considered a better alternative in some circumstances. Ages and Stages. Healthy Living. Safety and Prevention. Family Life. Health Issues.

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