MULTIPLE PREGNANCIES

The human female usually  has only  a single baby  in each pregnancy, but sometimes,  one pregnancy in ninety is a twin pregnancy,  a triplet or  quadruplets. There are two ways in which a multiple pregnancy can occur. Either two or more eggs are released  from the ovary at one time and each egg is fertilized by a different spermatozoon  or the single fertilized egg may completely divide at the stage of the blastocyst and then two individuals develop with different placentas.

The  first kind of twins are fraternal twins who are  no  closer to each  in characteristics than any brother or sister. The second  kind are indentical twins and are mirror images of each other. Fraternal twins make up 75% of all twin pregnancies while identical twins make up 25%.
Twins  are frequent in africa and Asia  countries and this is due to the higher proportion of fraternal twins as identical  twins occur equally often whatever the race or age of the mother . Among Caucasians and Europeans , fraternal twins occur more frequently in families  with a history of twins, in older women, among women who have  had several children previously and  after injections of drugs which induce  ovulation.
Each twin is always lighter  than a  single baby at the  same stage of  pregnancy although the combined  weight of the  twins is greater than that of a single baby. Because of this, twins  tend to be  underweight at birth.  As well, the size of the twins can vary very considerably.  The difference between them is greater when  they are identical twins, as one is greedy and takes the greater part of the nourishment which arrives through the placenta. Inside the womb, the twins lie side by side. In late pregnancy,  it has been shown that  in 45% of cases, both lie with their heads over the mother's pelvis,  in 25% the leading twin has its head down and the other twin is a breech. In 10%, the breach leads and in 10%, both  are breeches.
The doctor may suspect twins when he finds that the uterus is larger than  normal caculated from the date of the last period. There are other causes for the undue enlargement  of the womb but twins is the most  common cause. It is possible the doctor will be able to feel both babies but this is unusual before the 28th week of pregnancy by which time the expectant mother herself suspect that she is carrying twins. If the doctor is uncertain, he will  arrange for an ultrasound picture which will show the two babies and their position in the uterus.
A multiple pregnancy is a little more risky than a  single pregnancy but provided the expectant mother goes regularly for antenatal care,  the risk is small. A raised blood pressure and anaemia are common. In  late  pregnancy, twins usually impose more discomfort on the expectant mother than does a single baby. Her abdomen feels heavier, she has more backache and swelling of the ankles and legs is quiet common. It has also been found that twin pregnancies tend to end  prematuredly and about one-quarter of twin babies are delivered by the 36th week. This premature rate can be reduced considerably with good antenatal care and if the mother rest for  a good deal of the time from the 32nd week. She does not  need to be in hospital if she can rest at  home unless she develops a raised blood pressure.
Contrary to popular belief,  labour in a twin pregnancy  does not last longer than in a single pregnancy although the delivery  may have to be aided by a doctor.  The knowledge that a woman has a  multiple pregnancy may have a psychological effect on the  woman and on her partner. Also,  after the 20th week of pregnancy, a woman bearing twins has a higher chance of developing complications  which require admission to hospital. If she already has a child or children, her absence from home may require that relatives provide help. After the birth, the demands of caring for two babies may also affect their sexual relationship. However, this need not happen if these issues  are thought about during pregnancy and arrangements made to reduce  the stress.