Birth of two or more children at once in our time is not uncommon. Multiple pregnancies happen more often every year. Twins and triplets no longer cause such a storm of emotions, as before. However, their birth is still not fully understood phenomenon. So, what is a multiple pregnancy: twins, twins - the topic of discussion for today.
In multiple pregnancies, two or more fetuses develop simultaneously in the uterus. Depending on their number, later they are born: twins, triplets, quarters and so on. The most common form of multiple pregnancy in a person is a single-egg pregnancy. It can arise from a single fertilized egg and from one spermatozoon. Growing up in such a pregnancy, twins, as you know, are absolutely identical. They are always of the same sex and have the same genetic code.
Multiple pregnancy can also be the result of fertilization of two separate eggs with two separate spermatozoa. As a result, two fetuses develop, which can be of one or different sex, and their genetic codes are not identical. But still, they, like in the first case, are also called twins. They are to each other brothers and sisters in the same degree as brothers and sisters from two separate pregnancies.
Multiple pregnancy in facts and numbers
It is assumed that the fertilization at which twins are born is a pure accident. This fact has no influence on heredity or any internal or external factors. Their number is relatively constant and is about 0.4% of the total number of births. According to some researchers, for every 80 births there is one birth of twins.
However, in the course of many years of research, certain patterns were revealed. So, the conception of twins depends on many factors. The most important are: heredity, race, environment, the age of the mother and her degree of fertility, as well as the hormonal level.
The lowest percentage of multiple pregnancies is observed in eastern countries, the highest in African, and the average in Caucasians. In China, this figure ranges from 0.33 to 0.4%, and in Western Nigeria is approaching 4.5%. In Caucasians, the percentage of birth of twins in relation to the total number of births is from 0.9 to 1.4%.
The frequency of multiple pregnancies strongly depends on the age of the mother. The lowest percentage (0.3%) was found in women under the age of 20 and over 40, and the highest (1.2-1.8%) at the age of 31-39. The likelihood of the birth of twins also increases with the number of births. It was found that the possibility of multiple pregnancy is greatest in the third or subsequent delivery.
Mothers of twins are most often unmarried women, women with excess weight, and also those who have late started to lead a sexual life. The formation of multiple pregnancy is more likely with the greatest number of sexual intercourse. Most often, twins are born from pregnancies that began in the summer months. It also depends on the month of the birth of the mother - among women born in the period from January to May, more often there is a multiple pregnancy.
In general, it is believed that multiple pregnancies tend to repeat. It was estimated that after the birth of twins the probability of multiple pregnancy increases by 3-10 times! There is also the probability of hereditary predisposition. That is, there are more chances to give birth to twins in those in whose families there were cases of multiple pregnancies.
Since the beginning of the 1970s, there has been a marked increase in the number of cases of multiple pregnancies in the world. The causes of this phenomenon are believed to be an ever wider and more effective use of methods of artificial insemination and hormonal infertility treatment. The methods of artificial reproduction led to a situation in which the developed countries increased the birth rate of twins by 50%. All this is the result of medical intervention.
The Dangers of Multiple Pregnancy
Odnoyaytsovye twins are usually smaller in size, more often have congenital malformations and more often die in the womb than dysentery. Adverse conditions for intrauterine development, malnutrition, frequent umbilical cord loops, as well as a large number of premature births significantly worsen the prognosis of multiple pregnancies.
Studies of vascular compounds showed the presence of unusual arteriovenous malformations (vascular anastomoses), mainly in identical twins. These compounds can cause embryonic-fetal transfusion, which leads to disability or fetal death.
The more fruits in the uterus, the greater the amount of circulating blood, hypertension, swelling, enlargement of the heart, liver, kidneys. As a result, polyhydramnios can develop. The size of the fetus decreases, it pales, its growth stops. This condition is characterized by anemia, less blood circulation, dehydration. In this situation, both fetuses are at an increased risk of heart defects. Interruptions in the placental circulation can lead to damage or impairment of fetal nutrition (one or all).
Complications of the mother
Gestosis and eclampsia occur three times more often with multiple pregnancies than with normal pregnancy. In 75% of cases, multiple pregnancy ends in premature birth. The systolic state of the uterus is weak and disjointed. Placenta previa is most likely. In this case, the size of the placenta with multiple pregnancies is much higher than in normal pregnancy. This creates a danger of internal bleeding and seizures. As a result of rupture of the amniotic membrane of the first fetus or strong contractions of the uterus after the birth of the first twin, premature detachment of the placenta often occurs. The uterus is overextended during pregnancy, often without the ability to constantly contract after childbirth. And although postpartum atony is a common phenomenon, with multiple pregnancies this can cause severe bleeding.
Complications of the fetus (one or more)
Prenatal complications occur much more often than with usual pregnancy. This may be due to umbilical compression of the brain, eating disorders or congenital malformations. The greatest risk of neck compression of the umbilical cord is observed in the case of mononuclear twins with a single amniotic cavity. Almost twice as many odnoyaytsovyh twins and twins die during pregnancy and immediately before childbirth. The risk to the fetus is higher, relative to their total number.
Environmental complications are the most common cause of fetal death in multiple pregnancies. Early birth at least one month before the term is the result of the premature release of the baby from amniotic fluid and premature contractile activity of the uterus.
Factors that increase the level of mortality and fetal malformations depend on their location. This affects the general circulation of blood and the risk of surgical intervention. The prolapse of the umbilical cord takes place at a multiple pregnancy 5 times more often than with the usual one. The cause of cessation of breathing and death of the fetus may be, for example, clamping his head in the wrong position before childbirth. A special case is the so-called complications of Siamese twins, in which birth by a natural way is simply impossible.
Postpartum complications - the survival of newborns in multiple pregnancies depends on both the type of obstetric complications and the condition of the fetus, care for the newborn and many other factors.
What are the chances?
The best result is when both fetuses are in the "head down" position, at which birth can naturally occur.
Maternal morbidity in multiple pregnancies is 4-8 times higher than in normal pregnancy. Maternal mortality increased only slightly. If the child was born alive, the best criterion for survival is the gestational age. In most cases, the prognosis for twins or triplets weighing more than 2500 g is better than for single fruits of the same birth weight. This follows from the fact that the fruits of multiple pregnancies are more mature.
The second of the twins, as a rule, is in greater danger than the first. It is often smaller in size and has cardiovascular disorders and perinatal injuries that can cause it more harm.
Same or not?
With multiple pregnancies, twins, twins, triplets and so on can be very difficult to distinguish. There are often situations where parents of identical twins can not distinguish their own children. In the case of the birth of twins, about 10% of parents recognize the fact that they are not able to name a child by name, since they have just confused who is who.
The similarity of twins in the sense of close communication is sometimes the cause of many internal dilemmas associated with a complete lack of sense of individuality. Mark Twain in his autobiography says that after the loss of his twin brother, he was often tormented by the question: "Which one of us is actually alive: he or I."
Siamese twins
Siamese twins, even in our time, are still a biologically unexplored phenomenon. For an unknown reason, two fetuses grow together even before birth with different parts of the body. The first successful division of Siamese twins occurred in Thailand in 1951 and this operation was performed when the twins were two years old. Thailand was known then as Siam. Hence such twins, fused with each other, and began to be called "Siamese." Today, with the participation of diagnostic equipment, it can be concluded that not only some parts and organs are common in twins, but also very close vascular connections between them. Sometimes, fortunately, Siamese twins can be divided. However, medicine still knows very little about this phenomenon.