Generality
Twin birth is the way in which two or more children are born, at the end of a multiple (or multi- fetal ) pregnancy .
Depending on the health conditions of the future mother and the twins, the birth can be carried out naturally or by caesarean section .
Generally, vaginal birth is possible when the pregnancy has come to an end without significant problems and the presentation of the first of the children is cephalic.
If these conditions are not present or there are more than two twins, a caesarean section is scheduled.
What's this
Twin birth: definition
As the word itself suggests, the twin birth consists in the birth, natural or cesarean, of one or more twins . This event occurs at the end of a multiple pregnancy, between 32 and 38 weeks .
Twin birth: preliminary overview
- Multiple pregnancies are diagnosed by routine ultrasound at week 18-20 . As a rule, the twin birth involves the birth of two children . The cases of multiple births are, however, more rare.
- Twins can be of two types:
- Monozygotes ( monovular twins): they are formed by the fertilization of a single oocyte by a single spermatozoon ; before reaching the uterus, the product of conception separates into two or more independent parts, but each able to give rise to a complete individual. The monozygotic twins resemble each other so much that, in general, it is difficult to distinguish them. Their genetic heritage is identical. The number of amnios and chorion depends on the moment in which the separation took place, so the pregnancy of monozygotic twins can be bicorial or monochorionic .
- Dizygotes ( biovular twins): it occurs by the fertilization of two oocytes by two spermatozoa . In this case, the unborn children can look alike or be different, just like all the other brothers and sisters. Dizygotic twins develop into two distinct chorionic envelopes ( twins twin pregnancy ).
How it happens
During gestation, the specialist visits and the health conditions of the future mother allow us to establish when it is possible to give birth naturally or if it is necessary to resort to a cesarean .
The travail of a twin birth does not differ from that of a single birth and, until the birth of the first child, everything proceeds in the same way.
In the case of natural twin births, therefore, the FIRST TWIN is born as if it were alone.
The expulsion of the SECOND TWIN occurs in ways that depend on its position:
- If the second twin is cephalic, that is it has the head turned towards the birth canal and the vaginal exit, it descends into the mother's pelvis along the pelvis, as happens in a normal natural birth.
- If the presentation is breech, the gynecologist looks for the feet and the baby is let out (note: before this maneuver the administration of oxytocin, the hormone that induces contractions, is suspended to leave the necessary space). Compared to a normal breech birth, the second twin has less difficulty in being born, as the first twin has already "paved the way".
- If the child appears crosswise, in an attempt to bring him to a position more favorable to the twin birth, an obstetrical maneuver of turning and extraction is performed.
Sometimes, the expulsion of the second twin is difficult or impossible: in these cases it is necessary to resort to cesarean.
Course of the Twin Childbirth
- Dilation : in the twin birth, the dilation phase, during which the inferior segment and the neck of the uterus widen until reaching a diameter that allows the passage of the fetus, is unique .
- Expulsion : it depends on the number of the fetuses, so it can be twofold if the twins are two, triple when they are three and so on. Once the first child is born, before the second child is expelled, an interval of 15-30 minutes occurs, during which the uterus adapts its size to the reduced volume of its contents (represented by the second twin). After this phase, the contractions can begin to act on the second child, to determine its birth. It should be noted that twins are generally smaller, so the expulsive phase will probably be simpler than that of a 4 kg child.
- Secondary : once the twins have been expelled, the secondment usually occurs, that is the last phase of the birth that occurs approximately in the quarter of an hour after birth. In the twin birth, this process is generally unique : the placenta (s) of the various fetuses are expelled all together, with the corresponding ovular membranes. In some cases of twin biovular pregnancy, it may happen that after the first fetus the corresponding appendages are expelled (in other words, the various phenomena follow one another exactly as in normal delivery).
Natural Twin birth
Natural twin birth requires a series of special conditions in order to take place:
- At the time of delivery, the presentation of both unborn babies must be cephalic (ie with the head turned towards the vagina, ready to go out). Natural childbirth can also be considered when at least one of the twins has this " upside down " position.
- The health conditions of the pregnant woman must be good, that is, the future mother must not have any kind of disorders at the end of the twin pregnancy.
- The pelvis must be large enough and the expectant mother must cooperate with the thrusts .
If even one of these conditions does not occur, and an episiotomy is not enough to assist the twin birth, the medical team will opt for the caesarean section.
Cesarean Twin birth
The use of cesarean section is indicated to simplify the birth of children, if there are situations that could complicate the natural twin birth, such as:
- Both unborn children are in a breech position (ie with their feet facing the birth canal);
- Pregnancy is multi-seeded (from 3 children upwards );
- One of the two (or more) twins has a growth delay or a large weight difference (note: in the case of monozygotic twins, if a child weighs 25% less than the other, the cesarean twin birth is indicated because there is the risk of fetal fetal transfusion);
- The placenta is prior, that is inserted in front of the neck of the uterus. When the placenta is in front of the fetal presentation, it can cause serious bleeding, when the dilation begins in view of the twin birth and after the birth of the children.
Unlike natural childbirth, caesarean section is programmed by the medical team, generally around the 37th week of pregnancy, if there are no problems that lead to anticipation. Therefore, the expectant mother does not expect to spontaneously enter labor.
A recent scientific study, however, has shown that, in the case of twin pregnancy, a cesarean is no longer effective in terms of reducing the risk of neonatal death compared to an induced vaginal birth.
Fetal-fetal transfusion syndrome
In the case of monozygotic twins, there is a risk of fetal-fetal transfusion, that is, the blood vessels feed one of the children to the detriment of the other, which grows less and runs more risks at the time of delivery.
Twin birth: how many weeks?
Normally, the twin birth occurs between 32 and 38 weeks of gestation, due to the greater enlargement of the uterus. More in detail, in the bicorial pregnancy (ie with two distinct placentas), the ideal term is fixed at 37 weeks, while in the monochorionic one (more rare) at 36 .
If labor does not occur by the 38th week, a caesarean will tend to be scheduled or birth will be given within this period.
How long is a Twin Birth?
Usually, only a few minutes elapse between the birth of the first and that of the second fetus, unless complications occur. Indicatively, the time interval between the expulsion of a twin and the other does not exceed 15 minutes, although it can vary from a few minutes to about three quarters of an hour, depending on the time required to engage in the channel of childbirth.
The twin birth runs less rapidly than the single one. The reason for the superior duration is attributable to the overdistension of the muscular fibers of the uterus, secondary to the greater content represented by the twins, for which the contractions are less valid.
During the twin birth, this phenomenon can be accentuated up to the end of labor pains; this condition is called uterine inertia .
Another situation that can affect the duration of twin birth is the abnormal presentation of twins:
- In the case of the first unborn child, this may depend on the second fetus, which may hinder its proper engagement within the uterus;
- In the case of the second twin, on the other hand, it must be kept in mind that, after the expulsion of the first twin, it suddenly finds itself in a very large cavity, so it can easily assume abnormal positions.
Besides affecting the phase of expulsion of the twin birth, these conditions can predispose to prolapse of the umbilical cord or traumas of one of the two fetuses .
Risks and complications
Before the twin birth
Multi-fetal (or multiple) pregnancies increase the risk of:
- Intrauterine growth delay;
- Premature labor;
- Placental detachment;
- Congenital malformations.
The perinatal morbidity and mortality of fetuses is related to the risk that various complications may occur, such as:
- Asphyxiation;
- Prematurity;
- Prolapse of the umbilical cord;
- Abnormal presentations;
- Polyhydramnios;
- Gestosis.
During the Twin Birth
Compared to a single birth, the birth of two or more twins presents greater difficulties and risks, both for the expectant mother and for the unborn.
Among the situations that can complicate twin births are:
- Crimping by the other fetus : a serious occurrence of twin birth is the simultaneous commitment of the two fetuses or, indeed, the clogging of one of the fetuses by the other. This situation is fortunately rare and usually occurs in the monoamniotic uniovascular pregnancy. The consequence is the arrest of childbirth and the inevitable death of at least one of the twins (that is, of the fetus that has suffered the bumping).
- Placenta previa : this condition complicates the twin birth, as it hinders the expulsion of the fetuses. In this case, in fact, the placenta implants, in correspondence of the inferior segment of the body of the uterus, so that it comes to be in front of the fetus at the moment of birth.
Even during the period of secondment, the risks are greater than with single births. In particular, it is possible that the uterine muscle fibers, which are overdosed during pregnancy, are not able to ensure a sufficiently strong contraction to compress the blood vessels that remained open after the detachment of the placenta. In this case, we speak of uterine atony .
Other complications that may occur during twin birth include:
- Incomplete detachment of the placenta (s) : it occurs fairly often and represents a serious danger for the maintenance of the physiological hemostasis.
- Haemorrhage : the amount of blood lost may be greater than that occurring during a single birth, due to hyper relension of the uterus.
- Endothelial asphyxia of the second twin: in some cases, the considerable retraction which meets the wall of the uterus after the expulsion of the first fetus can hinder the flow of blood per second; at other times, this event may even determine the detachment of the placenta before the expulsion of the fetus. The result can be a serious insufficiency of the blood supply to the unborn child. For this reason, if the presentation with respect to the birth canal is unfavorable, a period longer than 15 minutes is not allowed for the expulsion of the second fetus and an emergency cesarean is implemented.
After the Twin Childbirth
As for the pregnant woman, due to the traumatizing action of the various obstetric interventions that may be necessary and the possible complications listed above, the prognosis in the twin birth is less favorable than in the single one.
After the birth of the twins, the main maternal complications are uterine atony due to hyperdistension, urinary infections and postpartum hemorrhage . To prevent the latter occurrence, immediately after the birth of the second twin, doctors increase the dose of oxytocin administered to the woman, to favor the contraction of the uterus and block excessive blood loss. Moreover, in the delivery room, a supply of blood is always available for the possible need to carry out a rapid transfusion.
Some advice
- For the future mother, the twin birth can be a particularly "intense" event both from a physical and psychological point of view. In order to face the birth of their children peacefully, it is useful to attend a prepared course . For the expectant mother, being well prepared on what will happen at the time of the twin birth can help to alleviate worries. Likewise, the interview with your gynecologist helps the expectant mother to have certain and essential information, to give birth to children safely.
- Except in cases where it is contraindicated, the patient may request an epidural .
- Thanks to ultrasound monitoring, the diagnosis of a twin pregnancy is not difficult. To carry out the birth, it is advisable for the expectant mother to contact a hospital where she can find the most appropriate assistance.
