Fraternal twins have different life spans. Multiple pregnancy: how did it happen? What is the probability of having fraternal twins?

The occurrence of twins accounts for about 1.5% of all newborns. Modern medicine still can't say for sure why this happens. It is known that a hereditary factor plays a role, for example, 31 women out of 300 had multiple pregnancies in their relatives. In addition, the likelihood increases after discontinuation of hormonal contraceptives that have been taken for a long time.

What are twins like?

Twins can be identical or fraternal. When, at the very first stage of pregnancy, a fertilized egg is divided into two or more parts, each of which is formed as an independent organism, identical twins, or monozygotic, are born.

They are always the same sex, very similar in appearance, have the same set of genes, and often suffer from the same diseases at the same time.

Fraternal twins, or fraternal twins, as they are popularly called, develop from not one, but two eggs that mature simultaneously in the ovary(s), and each of them is fertilized by different sperm. Such children are different, like ordinary brothers and sisters born in different time. The genetic structure of such children is completely different.

They may have different blood types and genders, facial features and character. The main difference between fraternal and identical twins is that their genetic similarity is 40-60%, that is, like ordinary brothers and sisters.

There are also widely known cases of so-called Siamese twins. This phenomenon was first noted in Siam (Thailand) at the end of the 19th century. Siamese twins develop from one egg that begins dividing into more later. As a result, the division is incomplete.

Causes of multiple births

In addition to hereditary predisposition and hormonal drugs There are several other factors that increase the chances of having multiple children:

• Identical twins can be born due to increased production of a hormone that stimulates the maturation and development of eggs;
• Women aged 35 to 39 also have an increased chance of having twins. This is explained by the fact that before menopause there is a kind of hormonal surge, therefore late pregnancies quite often multiple;
• It is impossible not to mention IVF - in vitro fertilization. According to statistics, it is not uncommon for women after IVF to have several children at a time. This phenomenon is caused by the use of drugs for the treatment of infertility.

Diagnosis of multiple pregnancy

This fact can be established already in the first trimester: the size of the uterus significantly exceeds the norm for a singleton. By the end of the third month this becomes even more noticeable. This assumption can be confirmed using ultrasound. It also happens that the first time two fertilized eggs were discovered, but at the next planned examination only one. This happens when one of them dies.

Using ultrasound, specialists must determine the identity of the fetuses - identical or fraternal twins, as well as chorionicity (the number of placentas). The study should be carried out up to a maximum of 14 weeks, since based on the data obtained, the supervising doctor draws up a pregnancy management plan.

Also, the timely detection of complications characteristic of monochorionic twins depends on this information. For example, feto-fetal transfusion syndrome may occur. In addition, you will need to choose a delivery option.

The results of the trigeminal test are not taken into account. The development and condition of the fetus is judged by the indicators of alpha-fetoprotein, human chorionic gonadotropin and placental lactogen. These data make it possible to identify defects and chromosomal pathologies. But with multiple births, regardless of the number of placentas, much more of these substances are produced.

Multiple pregnancy: features of the course

This phenomenon requires increased attention, since a woman’s body is designed to bear and feed one baby. Therefore, even during pregnancy, twins fall into the so-called biological risk group. In the first trimester, there is a high probability that one of the fertilized eggs will die.

Due to an increase in erythropoiesis in the second half of pregnancy, iron reserves may be depleted, which provokes anemia. To monitor the condition of the woman and the fetus, blood smears are examined.

In a woman, the diaphragm shifts significantly, the work of the heart and lungs becomes difficult, increased fatigue and shortness of breath are observed, frequent urge to urination and constipation. Toxicosis and varicose veins also often occur.

In this case, the threat of premature birth or miscarriage may develop in the second and third trimester.

The main reason is excessive stretching of the uterine muscles due to the large volume, which provokes labor. Therefore, women with twins are often prescribed medications to relax the uterus.

To reduce the risk of premature birth, the condition of the cervix is ​​monitored. If it shortens, stitches are placed or a pessary is installed.

Carrying twins is often accompanied by incorrect position and presentation of the fetuses, for example, pelvic, transverse. This factor is decisive in choosing the method of delivery.

To monitor the condition and development of the fetus, dynamic fetometry and Dopplerometry are used. It is worth noting that twins may grow differently, for example, one may be developmentally delayed.

Women with multiple pregnancies are also more likely to suffer from urinary tract infections. This is due to a violation of the normal outflow of urine and the position internal organs due to a significantly enlarged uterus. Such expectant mothers require more careful clinical and laboratory monitoring.

The weight of a pregnant woman is also not ignored. The difference is that in a singleton pregnancy the norm is 9-15 kg, but in the case of twins, body weight can increase by another 20 kg. A woman's diet should be balanced, but not high in calories. If edema occurs, the amount of fluid per day is reduced to 1.5 liters.

Childbirth process

A woman with twins is sent to the maternity hospital several weeks before the expected date of birth. As a rule, birth occurs at 36-37 weeks. The most favorable period for twins is considered to be 36-38 weeks, for triplets - 34-36.

The birth process itself can occur naturally. A cesarean section is not always prescribed for multiple births. However, some complications may arise in the process: untimely release of water, loss of part of the umbilical cord, or the arms/legs of the fetus.

The birth of several children during one pregnancy is a mystery that has not been completely solved even in the modern age of high technology. About one woman in a hundred gives birth to twins. The risk of multiple pregnancy increases several times if there are already twins in the family.

Causes of multiple pregnancy

Why a woman gives birth to two instead of one child, and in rare cases even more, scientists do not know for sure. The trigger that causes the body to produce two eggs or to separate one incorrectly has never been identified.

Doctors give the following reasons occurrence of multiple pregnancy:

Monozygotic pregnancy

A monozygotic pregnancy, which produces identical twins, occurs when one egg is fertilized by one sperm, but its development fails and two embryos begin to develop. The factors that influence this division of the egg after fertilization have not been established. The timing is also unknown. when two organisms emerge from one cell. During the research, it was found that multiple pregnancies from one egg occur due to the division of the zygote.

Signs of identical twins:

There are several options for the development of monozygotic pregnancy:

1. The zygote divides in the first days after conception. Because of this, embryos each form their own amniotic sac and placenta. At the diagnostic stage, this form is often confused with fraternal twins.
2. The zygote divides in the first week of conception. In this case, both embryos receive their amnions, but they still have a common placenta. This can cause one child to be suppressed by another even in the womb.
3. Separation occurs after a week. These are very rare cases. With this course, the embryos are in one fruit sac. This is considered dangerous: during pregnancy and childbirth, identical twins can become entangled in each other's umbilical cords or cause injury to each other.
4. Separation occurs after two weeks. Two weeks after conception, the formation of the embryo begins. Separation at this stage results in conjoined embryos or conjoined twins. Most of them are not viable and have developmental defects. As a rule, they die during development in the womb or at birth.

Heterozygous pregnancy

Heterozygous or fraternal babies appear if two embryos are simultaneously conceived in two different eggs. This type of pregnancy occurs most often. The formation of two eggs at once in one menstrual cycle can occur due to external and internal factors: when taking hormonal drugs, during IVF and with a hereditary predisposition.

Signs of heterozygous pregnancy:

The probability of pregnancy is quite high: one in a hundred. When heterozygous, conception occurs in two eggs, which are released from two ovaries at the same time. Such embryos have their own amniotic sacs, placenta and umbilical cord. Fraternal twins develop separately and have virtually no influence on each other.

Monozygotic polar pregnancy

Polar monozygotic twins are extremely rare. In this case, pregnancy occurs due to fertilization of the egg and its polar body. At conception, two sperm enter the cell at once. The rarity of the occurrence of such monozygotic twins is due to the fact that the embryos die in the early stages in most cases.

Signs of polar monozygotic twins:

• children are quite similar, but may have some differences in appearance;
• characters may be the same, but aspirations, hobbies, and ideals differ;
• Children may have different blood types;
• V future life children feel closeness and are good friends.

Features of the course of multiple pregnancy

During a multiple pregnancy, a woman has a greater risk than when carrying one child.

The following possible pathologies exist when carrying several embryos:

1. Impaired blood flow during monozygotic pregnancy, when one of the twins may experience hypoxia due to lack of blood.
2. Absence of one or more organs or body parts in one of the twins.
3. Death of one of the fruits.
4. Chromosomal disorders.
5. Developmental pathologies.

Multiple pregnancies must be carried out under the supervision of a gynecologist. A week before the expected birth, the expectant mother is placed in the maternity ward. If the number of children is no more than two and they do not have pathologies, natural delivery is allowed; in other cases, a caesarean section is performed.

Pregnancy with twins carries not only joy, but also enormous responsibility, because carrying two babies at once, twins or twins, is a serious burden on the body of the expectant mother. Today such a situation is not so rare. In approximately 0.7-1.5% of cases, twin pregnancies are noted. In case of multiple pregnancy, a woman needs Special attention by medical personnel due to possible complications. Only doctors can take into account the peculiarities of twin pregnancy and properly monitor the patient’s condition.

What is twin pregnancy?

This is the name of one of the types of multiple pregnancies (MP), when not one, but two fetuses develop in a woman’s sac. There may be more of them - triplets, quadruplets, etc. When carrying two fetuses, early diagnosis is very important so that in the future the woman’s condition will be under the strict supervision of a doctor. Based on the number of fertilized eggs, multiple births can be identical or fraternal. In the first case, the children are called twins, and in the second, twins.

Fraternal twins

This type of twin pregnancy is more common, in about 70% of cases. It occurs when two eggs mature in a woman’s body at the same time (in the ovary or ovaries), which are then fertilized by different sperm during one or two sexual acts, provided that no more than a week has passed between them. In this case, two isolated embryos are formed. These twins are called dizygotic or fraternal, and popularly called fraternal twins. They have only general similarities, like between brothers and sisters. Children rarely have the same sex; more often they are born different.

Such a twin pregnancy can only be bichorionic biamniotic (otherwise known as diamniotic dichorionic). It is characterized by the fact that:

• Each baby has its own sac with amniotic fluid (fetal bladder);
• each fetus has its own chorion (hereinafter referred to as the placenta);
• Dizygotic twins have 2 sets of membranes that surround the amniotic sac (the inner layer of the amnion and the outer layer of the chorion).

Identical twins

If a non-identical pregnancy with twins can only be bichorionic biamniotic, then an identical (monozygotic) pregnancy has several types depending on the time when the egg divided. This happens after fertilization. The following types of monozygotic MB are distinguished:

1. Monozygous bichorionic biamniotic. Occurs in approximately 1/3 of cases. The division of the egg occurs as it moves through the tube to the uterus. This is the period during the first three days after fertilization.
2. Monozygotic monochorionic biamniotic. Occurs when the egg divides from 3 to 8 days after conception. In this case, 2 embryos are formed: each has its own amnion (fetal bladder), but they have a common chorion. This type of connection is typical for every 360 case. Because they share the same placenta, such twins are at risk.
3. Monozygotic monochorionic monoamniotic. Occurs in every 2400 cases. Separation occurs 8-13 days after conception. In this situation, the embryos share a common amniotic sac (amnion) and a common placenta (chorion). Such a twin pregnancy is considered the most unfavorable. Monoamniotic twins are at risk of death due to possible tangling of the umbilical cords during the growth of the babies.
4. Siamese twins. Appear when separation occurs later than the 13th day after conception. Children can fuse their tailbones, skull bones, lumbar spine or chest.

Causes of multiple pregnancy

The main reasons for the birth of twins are the maturation of several eggs at once in one uterus or the division of the zygote into two parts after fertilization. Particular factors for the occurrence of multiple pregnancy are:

1. Genetic predisposition. Heredity has a high degree of influence. When spouses in a relationship have had twins, they are also more likely to have twins.
2. Age. During premenopause (up to 35 years) not every menstrual cycle ovulation occurs. They alternate with ovulatory ones, when a surge of hormones occurs. If ovulation occurs after this, then 2 or more eggs mature.
3. Hormonal contraception. The abolition of such drugs leads to the activation of the synthesis of one’s own hormones, which leads to the maturation of several eggs.
4. In vitro fertilization (IVF). Thanks to modern reproductive technologies, in case of infertility, conception can be artificially stimulated. A woman is given up to 4 eggs, which increases the likelihood of twins.
5. Birth of twins from a previous pregnancy. If a woman is pregnant again, she has a greater chance of having twins.

Signs of twin pregnancy

A woman may suspect she is pregnant with twins as early as early stage. The test shows a positive result the first time. This unusual condition is also determined by the following signs:

1. Toxicosis in twins. It starts earlier and lasts longer, until about 16-17 weeks. The woman's health is more difficult. Toxicosis is accompanied by vomiting and increased fatigue.
2. Rapid weight gain expectant mother. Body weight increases much faster from the first weeks, which is why a woman needs to strictly monitor her diet.
3. Belly with twins. Due to the growth of two babies at once, it begins to increase earlier. By the 12th week, the size of the uterus almost reaches the navel (with a singleton it only protrudes slightly above the womb). Due to the close presentation of the fetuses, the woman feels movement earlier.
4. Preeclampsia and anemia. In case of multiple pregnancy, these conditions are diagnosed in half of the cases. This is due to an increase in the volume of circulating blood and plasma. To prevent anemia, iron supplements are prescribed.
5. Swelling and shortness of breath. Due to the high load on all organs, it is difficult to carry twins without complications. Displacement of the diaphragm disrupts the functioning of the lungs, causing shortness of breath, swelling, and fatigue. Due to the heavy load, the risk of varicose veins is high.

How is twin pregnancy diagnosed?

There are several methods and signs that help identify multiple births. The doctor can determine it already during a gynecological examination, but in addition the woman is prescribed several procedures:

1. Blood analysis. It is necessary to determine the presence of human chorionic gonadotropin. This hormone is secreted by the placenta.
2. Ultrasonography. This method more informative only from the 8th week of gestation. Ultrasound in the early stages does not always detect twins, because one fetus can hide behind the other.

When examined by a gynecologist in the early stages

During the initial examination, the doctor may note several signs of multiple pregnancy. The gynecologist palpates the soft uterus - in this case, he notes the discrepancy between its size and the delay in menstruation. Other signs that the doctor notes if multiple births are suspected:

• beating of 2 hearts during diagnosis by the Doppler system;
• inflated AFP blood test results;
• discrepancy between the size of the head and the volume of the abdomen;
• too rapid weight gain;
• persistent constipation;
• severe swelling of the legs;
• excessive fatigue of a woman;
• severe toxicosis and gestosis in the early stages;
• high blood pressure.

HCG indicators in a blood test

An hCG test can confirm the doctor’s hypothesis. This indicator has specific values ​​for each week. If after analysis it turns out that the hCG level is too high for a certain stage of pregnancy, then this may indicate multiple pregnancy. But this sign is indirect. High level HCG is characteristic of certain abnormalities in fetal development and ectopic pregnancy. In addition, this method cannot determine how many fetuses are in the uterus, whether they have one amniotic sac and placenta or several.

Ultrasound diagnostics

The first ultrasound is possible at 4-5 weeks, literally immediately after a missed period. It does not guarantee confirmation of multiple pregnancy, because one child can hide behind another, but in most cases it confirms the doctor’s assumptions. Further routine ultrasounds help the doctor determine how many placentas there are, the presence of a septum (one or two amnions), the location and heartbeat of the fetuses, signs of developmental delays, and fusion between twins.

Development of twins by week of pregnancy

Women pregnant with twins are at increased risk, so they need special monitoring from doctors. To do this, you have to visit the antenatal clinic more often: every 14 days until 28 weeks, and then every 7-10 days. The gynecologist pays special attention to the woman’s weight during each examination. By the time of birth, a woman in labor should gain no more than 15 kg. Every extra kilogram increases the risk of complications during fetal development. In each trimester of pregnancy with twins, you can distinguish characteristics, which are always noted by the doctor.

1-10 week

Early on, a woman’s body begins to react to a twin pregnancy. This is manifested by swelling of the mammary glands and an increase in hCG levels. By the 8th week, embryos can already be detected on ultrasound - their size reaches 3 cm. The symptoms are the same as those characteristic of multiple pregnancy, but toxicosis appears earlier. By 10-11 weeks, future babies are approaching the end of embryonic development:

• their length is about 4.5 cm;
• hearts are formed;
• the weight of the embryos is about 5 g;
• the voice-forming apparatus begins to form;
• The faces are visible, the heads are very large.

10-20 week

During this period there is fast growth both fetuses, due to which the uterus greatly increases in size and leaves the pelvic area. This condition requires a woman to wear special clothes for expectant mothers. At week 16, during an ultrasound, you can already distinguish the sex of the babies and roughly calculate their weight. Other features of the development of twins at this stage:

• babies can clench their hands into fists, they show facial expressions, but they sleep almost all the time;
• children react to sounds;
• the rudiments of the organs of the digestive and excretory system appear, the intestines begin to work;
• baby can swallow a certain amount amniotic fluid and remove waste products through the bladder;
• from the 16th week, the baby’s movements are felt, from the 20th week it is already felt very clearly;
• The body length of babies is about 17 cm, and their body weight is 200 g.

20-30 week

At the next stage, women experience a significant acceleration of metabolism, and stretch marks appear due to the rapidly growing uterus. The struggle of babies in the womb for the correct position leads to constant tremors. The woman's back begins to hurt again. Inconvenience is caused by increased urination, increased fatigue, lower back pain and severe swelling. Other features of fetal development according to the twin pregnancy calendar:

• by week 25, fetal growth is 30 cm and weight is about 700 g;

• By appearance babies are already more like newborns; an ultrasound may reveal that one is larger than the other;
• by 28 weeks, babies are already viable and in case of premature birth they have more high chance survive compared to premature babies;
• by week 30, growth is about 35 cm, and the formation of the body is almost completely completed.

30-40 week

This stage is one of the most important. In the final trimester, the bone skeleton is formed in babies, the pancreas develops, and iron and calcium accumulate. The head and body become approximately the same size, so children look proportional. A large belly makes it difficult for a woman to sleep. In this case, it is recommended to lie on your left side; it is better to purchase a pregnancy pillow for this.

During this period, a woman should limit physical activity, devote more time to rest. At week 36, the woman in labor is scheduled to be hospitalized. Babies during this period are considered fully term:

• the sucking apparatus has been formed;
• height reaches 45-50 cm;
• weight is about 2.2-3 kg.

Features of carrying twins

The process of bearing twins depends not only on the type of multiple pregnancy, but also on the woman’s medical history. Many factors are taken into account here - whether the patient is giving birth for the first time or for the second time, what method of delivery took place last time. Separately, it is worth noting pregnancy after artificial insemination, i.e. IVF when the possibility of multiple births is high. Each case has its own characteristics of carrying twins.

After caesarean section

If the previous birth took place via cesarean section, the next one may have serious complications. Here we can distinguish two scenarios:

1. If there is a defective scar on the uterus, doctors may insist on artificial termination of pregnancy. Even if twins develop normally, it is still dangerous.
2. If, after a cesarean section, a woman has a scar on her uterus, then gestation is extended to 30 weeks. Then surgical delivery occurs. This is necessary to exclude possible uterine rupture and other negative consequences.

Pregnancy with twins after IVF

In this case, twins are explained by the fact that of the embryos that the doctor implants into the uterine cavity, two can implant into the uterine layer at once, and not just one. They attach and successfully continue development. In rare cases and only at the request of the woman, specialists artificially remove implanted embryos. In some cases, this may be necessary for health reasons. According to statistics, twins are born in 30% of IVF cases. The high percentage is explained by the fact that several embryos are implanted into a woman to increase her chances of becoming pregnant.

Delivery during multiple pregnancy

Carrying twins differs in terms and characteristics of the course. In this case, doctors pay special attention to the woman’s health, inviting them to appointments more often. People are admitted to the hospital for a certain period before the scheduled date of birth. By this point, the babies are fully formed, even though their weight and height are slightly below normal. If necessary, they are immediately sent to intensive care.

When can twins be born?

A peculiarity of multiple pregnancy is that women rarely reach the usual period of 38-42 weeks. Patients carrying twins often give birth at about 36 weeks. For this reason, women are hospitalized at least 14 days before the expected date of birth. In general, the favorable period for the birth of twins is 36-38 weeks. The peculiarity is that twins have a longer adaptation period than one baby. For this reason, even at birth ahead of schedule they can breathe on their own.

Natural childbirth

Delivery tactics are determined taking into account several factors. The doctor takes into account the position and presentation of the fetuses, especially the first baby. No less important are the regularity and intensity of contractions, the presence of water and intrauterine hypoxia of twins, the age of the woman in labor and possible gynecological diseases. Natural childbirth is used if:

• both fetuses are presented with their heads;
• the condition of the babies and mother is satisfactory;
• labor activity is regular.

Natural childbirth in most cases proceeds normally without any abnormalities, but can sometimes be accompanied by some complications:

• weak labor due to a distended uterus;
• premature rupture of amniotic fluid or placental abruption after the birth of the first fetus;
• fetal hypoxia;
• bleeding;
• prolapse of the umbilical cord.

Indications for abdominal delivery

In case of multiple pregnancy, doctors often do not take risks and resort to abdominal delivery, i.e. caesarean section. The undeniable indications for elective surgery are:

• extragenital diseases;
• unprepared birth canal for childbirth after 38 weeks;
• age of the first-time mother;
• pelvic or transverse position of the first fetus;
• complications during pregnancy with twins;
• severe gestosis;
• excessive distension of the uterus;
• large babies;
• polyhydramnios.

Possible risks and complications

Carrying twins is a serious challenge for a woman. The risk of complications in such patients is higher compared to a singleton pregnancy. Possible consequences classified depending on the time of appearance. They can be:

• intrauterine;
• perinatal;
• postpartum.

Specific intrauterine complications

• reverse arterial perfusion;
• threat of miscarriage;
• fusion of children (Siamese twins);
• a chromosomal disease in one of the babies;
• feto-fetal blood transfusion syndrome;
• congenital “deformity” of one of the babies;
• anembryony – the phenomenon of the death of one of the twins;
• antenatal death of one fetus.

Perinatal

Complications with multiple pregnancy may occur during delivery. Mortality rates are high here - about 5 times higher compared to carrying a single fetus. Other serious complications during the perinatal period are:

• hypoxia of one or two fetuses;
• slow dilatation of the cervix;
• anomaly of labor;
• premature placental abruption (especially for the second baby);
• bleeding during separation of the placenta.

Postpartum risks for mother and twins

Due to the high risk of complications, twin pregnancy is considered a borderline state between normal and pathological. Even after childbirth, mother and babies are at risk. A woman is at high risk of bleeding, inflammation of the uterine cavity (endometritis), or slow contraction of the uterus (subinvolution). The woman in labor is observed for another 2 hours after birth. If necessary, uterine contractions are administered.

Multiple pregnancy - photo

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