Archived Newsletters

TWINS Special problems of twinship

Although they are by far the most common of multiple births, twins still excite a great deal of wonder from parents and outsiders alike. What are the special problems of twinship and how should they be dealt with?

Q What is the difference between identical and non­identical twins?

A On a biological level, identical twins are the result of a single fertilized egg cell dividing into two identical cells which then separate and develop independently. Since both twins are derived from one sperm and one egg, they are genetically identical. Non-identical twins, on the other hand, are no more genetically similar than ordinary brothers and sisters. They develop from two different ova and have separate placentas.

Q Is it true that Siamese twins are actually identical twins, and that they can be separated by surgery?

A Yes, it is. In rare instances, identical twins can be born joined together, usually at the hip, chest or abdomen. Naturally they will be of the same sex, but may look radically different from each other. Sometimes they can be separated by surgery, but if they share a vital organ surgery will usually not be done.

Q I've read that if one member of a pair of twins dies at birth his or her twin feels incomplete for the rest of his life. Is this true?

A Yes. There have been reported cases where the dead twin had a lasting influence on the live twin, who lived with a dramatic sense of loss. In some instances this feeling of loss was diverted into a fantasy life which involved the dead twin, and this often influenced the pattern of the live twin's future relationships.

Q Is it possible for identical twins to look so alike that you can't tell them apart?

A Yes. A celebrated case was that of the 'Toni Twins' - identical twins who appeared in a series of advertisements in the 1950s. They underwent a series of tests twenty years later, and it was found that not only did they still look identical, but their fingerprints were the same, blood pressure readings were the same-even the cholesterol levels in their bodies were identical!

Fraternal twins

In a normal pregnancy only one ovum or egg is fertilized. However, if two ova are fertilized at the same time, fraternal or non-identical twins will be born. These twins may be of the same or different sexes, and can be as dissimilar to each other as any pair of siblings. This is because they grow from two separate egg cells fertilized at the same time.

The tendency to give birth to fraternal twins is inherited, especially through the mother's side. They tend to miss every other generation so that children of dizygotic twins are more likely to bear twins than to be born twins themselves. These twins also appear more frequently after the second pregnancy and if the mother becomes pregnant later in life. Research has shown that mothers aged 35-40 are three times likelier to have fraternal twins than mothers under 20.

Identical twins

In rare cases, if one ovum is fertilized, as in a normal pregnancy, but the resulting embryo divides at a very early stage and produces two embryos, monozygotic or identical twins will be born. Since these twins would originally have formed from the same ovum and sperm, identical twins will have the same genetic make­up; they will be of the same sex and have the same blood group, same build and the same physical characteristics.

Occasionally some pairs of twins have the same characteristics in reverse: for example, the hair of one twin may part on the right, while the other's hair part naturally on the left. These twins come from a common egg cell that did not divide until it had developed left- and right-sided characteristics.

Psychology of twins

The psychological development of twins is a fruitful area of scientific research - in fact, studying pairs of identical twins has led to valuable insights into distin­guishing constitutional characteristics from those that are acquired. More often than not, twins are quite different psychologically. Even monozygotic or identical twins raised in the same environment may have very different personalities. However, if one twin has schizophrenia, the other twin - especially if he is an identical one - runs a higher risk of developing the same condition.

 Very often, however, the bond between a pair of twins transcends any physical similarities. There are hundreds of 5tories, for example, of one twin feeling great pain when his or her twin has been hurt - even when they were miles apart. There are also accounts of one member of a pair of identical twins going through all the symptoms of childbirth when her sister was in labour. In fact, on a more basic level identical twin babies can show disconcerting psychological similarities. Often when one twin is reprimanded the other will act as if he or she is guilty as well. They will be happy at the same time, sad at the same time, bored in the same situations. In fact it is this constant process of identification with each other on the basis of their similarity of emotional experience which keeps identical twins 'identical' in spite of differences acquired in later life.

Twins and individuality

Some parents emphasize the twinship of their children by treating them as if they had no individuality: dressing them alike, giving them the same presents, or treating them as if they were one unit rather than two possibly very different individuals. This isn't very surprising ­the whole world is fascinated by twins, makes a fuss of them and likes them to look and dress alike. In some respects this could be dangerous: by throwing twins on to each other exclusively, the tendency of one twin to copy the other or become dependent on him or her increases. This may overstress the twins' normal identification with each other and thus produce a team relationship which may estrange them from their surroundings. Emotional disturbances may develop, especially if for some reason the twins have to be separated.

Even so, parents should not be afraid to dress their twins alike or to enjoy the attention the twins get because of their similarity - provided that it's kept in perspective. Twins. in fact, can develop great strength of personality from being twins, a capacity for playing together independently of their parents.

Feeding twins can be a problem. The majority of parents have found that it is essential to try to get the twins on to a schedule as soon as possible, and to feed both babies at once or one right after the other, or else they will be feeding all day and all night. Breast feeding is entirely feasible: as soon as the babies can nurse they can be put to breast together, either lying across their mother's arms or in her lap, one on top of the other, with heads at opposite sides.

Problems with twins

The mortality rate of twins in the womb is higher than that of single foetuses. This is because life in the uterus for the twins tends to be more difficult and twin preg­nancies are often associated with complications. Twins are also more prone to growth retardation and there is a higher rate of mental subnormality and congenital problems. Identical twins may run a higher risk of such diseases as leukaemia.


The odds against twins reaching 100 years of age are a staggering 700 million to one, but these American twins - pictured together at the turn of the century and celebrating their centennial birthday - have defied those odds!

Twinship taken to a happy extreme: these two pairs of twins met at a party, were married at a double wedding and lead virtually identical lives.

Non-identical (fracternal) twins result from two separate eggs that are fertilized at the same time by two separate sperm. Each twin develops its own placenta. Identical twins result when a single egg is fertilized and later divides. These twins usually share the same placenta unless the cells separate at an early stage of development.



Taken from The Marshall Cavendish A  to Z GUIDE IN WEEKLY PARTS,  DOCTOR’S ANSWERS: PART 90, TWINS, Page 2481 to 2483.


(All photos in the  script have been left out).

Back Back to top