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Pregnancy Bliss | Reproductive Health Hub

Continued from previous page

Is there anything of clinical importance in establishing the kind of twins that one is carrying?

Yes. Those twins with separate placentas (all non-identical twins and 30 per cent of identical twins) always fare best. They have the least number of complications.

Identical twins sharing a placenta have a potential of developing complications that never occur with those having separate placentas. These can be quite serious for both twins. Twins sharing a gestational sac fare worst and up to 50 per cent of these may be lost. Fortunately, these are the least common, accounting for about 1 per cent of identical twins and less than 0.3 per cent of all twins.

What are the problems unique to twins sharing a placenta?

Of most importance is the so-called "twin-to twin transfusion syndrome". This results from the fact that the twins may share some vessels and this may lead to one twin losing its blood to the other. Both the recipient (who is overloaded) and the donor (who is drained) are at peril. If this complication occurs early in pregnancy (before 20 weeks of gestation), the outlook for both is very bleak. The first to die is usually the recipient. When this problem manifests itself late in pregnancy, the situation can be salvaged but preterm delivery cannot be avoided.

What are the other problems associated with identical twins?

Twins sharing the same sac are prone to cord accidents, resulting from tangling of the cords. This accounts for the increased death rate of these twins. Birth defects are more common with identical twins and they are more prone to growMonochorionic (identical) twins (A.Rh)th restriction in the womb when compared to non-identical twins

Are there any other problems associated with twins in general?

Any multiple pregnancy, by virtue of this fact alone, is at increased risk of practically every potential pregnancy complication when compared to a singleton pregnancy.

Premature delivery is certainly commoner with twins or higher-order pregnancies. Only between 50 and 70 per cent of twin pregnancies reach term (37 weeks), compared to about 90 per cent of singleton pregnancies.

Prematurity is the single most common cause of morbidity and mortality among these babies. Perinatal death statistics show that up to 10 per cent of all twins are lost. This is several times the death rate among singletons.

Note: Perinatal deaths include those babies lost through stillbirth and those who die within a few days of delivery.

Even the rate of spontaneous miscarriage is several times higher than for singletons.

Complications such as  pre-eclampsia, anaemia and bleeding in pregnancy are also significantly more common.

What does a "vanishing twin" mean?

It is a well established fact that only a proportion of twins starting off as such actually continue as twins to delivery. If all twin pregnancies were identified early enough by ultrasound scan (at six to ten weeks), it is estimated that one twin will subsequently be lost in between 30 and 50 per cent of all.

Twins delivered therefore represent only a proportion of pregnancies that started as such and a substantial proportion of babies born as singletons started off as twins. The other twin, by implication, vanished. The twin that is lost, usually with such minimal symptoms and at such a very early stage of the pregnancy that the mother hardly notices, is known as a 'vanishing twin'. page

A pair of identical twins in the first trimester. These two are sharing a placenta but are in two separate sacs. The dividing membrane is too thin to visualise in this scan image.

Probability Fertility drugs Identical Vanishing twin TTTS Twin delivery Fetus in fetu Twin death