Many women dream of giving birth to twins. This is such happiness: your child will never be alone, he will have someone to play with and chat in the evening before going to bed. Having seen the treasured two strips on the test, many of them run to the doctor, cherishing the hope of hearing the treasured words. But the gynecologist is slow and waiting for something. When does an ultrasound show twins? And is everything so simple with multiple pregnancy?
Opposite twins
The phenomenon of twins still does not have a clear scientific interpretation. Of course, the mechanism of the birth of twins has already been well studied, but the factors that influence the development of multiple pregnancy without medical intervention are not yet understood by scientists.
In the case of the appearance of heterozygous twins, a woman ovulates not one, but two eggs, which fertilize two sperm. Doctors tend to explain this with hormonal disruptions in the body of the expectant mother, which can be triggered by the use of hormonal contraceptives, stress or stimulation.
In some cases, a hereditary factor also plays a role: about 10% of women have a genetic predisposition to double ovulation. However, its reasons have not yet been clarified.
In the case of such a pregnancy in a woman, babies have a different set of genes and chromosomes, can be of different sexes and are no more similar than regular brothers and sisters. Such twins on ultrasound can be seen when both embryos are already fixed in the uterus. Dates vary from 5 to 8 weeks.
Homozygous twins
There is another mechanism for the appearance of twins. It happens that a woman ovulates one egg and fertilizes her with one sperm. Everything goes according to plan, until under the influence of factors unknown to science, the zygote is not divided into two, each of which turns into an embryo.
The result of this process is the birth of identical or identical twins. Children in this case have the same set of genes, they are of the same sex and are usually very similar. Interestingly, the fingerprints and retinal patterns of such twins are still different. If the cell begins to divide late, or during this process a genetic malfunction occurs, then the probability of the birth of Siamese twins is high.
Such twins on ultrasound will not be immediately visible. However, by the first screening of 11-13 weeks, there is a high probability of finding two babies.
Where did the second come from?
Ideally, the first ultrasound of a woman is done immediately after applying to the antenatal clinic: 1.5-2 weeks after the delay of menstruation or at 5-6 obstetric weeks.
This is not a full screening, but a diagnostic procedure to determine the presence of a fetus in the uterine cavity. Such an early diagnosis eliminates an ectopic pregnancy.
And so the first ultrasound shows one fixed egg, and the calmed and satisfied expectant mother sets off to get used to her new status. And the more she will be surprised when after about a month and a half at the first screening the uzist doctor congratulates her on a multiple pregnancy. Where does the second baby come from?
Each female body is individual, and what week the twins are seen on an ultrasound scan entirely depends on the characteristics of the mother. The second embryo at the time of the first study may still not reach the uterine cavity. Indeed, sometimes fertilization occurs not on the same day, but in world history there are cases when the twin brothers were born to a woman from two different men.
In the case of homozygous twins, the explanation is even simpler: by 5 weeks, the zygote has either not yet begun to divide, or its division is so small that no, even the most qualified, doctor can still determine the presence of two babies.
Where did the second go?
The majority of doctors, when asked when to see twins on an ultrasound scan, will name a period of 5 to 10 weeks. But not every one of them is in a hurry to please a woman with a message about a multiple pregnancy. Why it happens?
It often happens that one of the embryos does not develop, and it can be absorbed by the placenta or the second twin. If development stops in the early stages, the cell may dissolve or simply remain in the uterine cavity until delivery. In this case, the doctor will find a fetal egg at subsequent ultrasounds, which does not pose any threat to either the mother or the second child.
Surprise Second Screening
However, a message about the presence of a second child can wait for a woman at the second screening, at about 16-20 weeks. How is it that a doctor cannot see two children before?
The presence of embryos in the uterus is established according to several signs: a heartbeat, the presence of two amniotic membranes filled with amniotic fluid, as well as two placentas. Can I see the twins on an ultrasound scan right away?
Yes and no. When each of the children has its own placenta and bladder, and this, as a rule, is a variant of different twins, it is not difficult to determine their presence.
With identical twins, development can go in two different ways. Both children have one placenta for two, but they can be located in both one and two amniotic membranes.
If the children are in the same bubble, then their visualization in the early stages is extremely difficult. Therefore, monochorionic monoamniotic twins are, as a rule, a big surprise of the second screening.
Other indirect signs of multiple pregnancy
Due to the imperfection of the medical system, not every pregnant woman, especially in the province, is assigned the first diagnostic ultrasound. Usually, doctors are limited to a blood test and a manual examination. Here are a number of indirect signs by which the gynecologist may suspect the twins and appoint an additional examination:
- extremely high levels of hCG and ACE;
- severe anemia;
- the size of the uterus that does not match the gestational age;
- early movements;
- the presence of pathological toxicosis and fatigue;
- fast weight gain.
However, a multiple pregnancy is far from always accompanied by some special phenomena. Many women continue to feel good, even when twins or twins are seen on an ultrasound scan.
Norms and terms of development
While future mothers are wondering whether twins can be seen on an ultrasound, doctors and scientists conduct research, systematize the data and find out how to determine the pathologies of the development of children from multiple pregnancy in the early stages.
Due to the presence of two children in the uterine cavity, visualization is often difficult. Despite the modern equipment that allows conducting research in 4D format, when twins on ultrasound are clearly visible, determining the size, gender and weight of each individual fetus sometimes causes problems even for an experienced specialist.
To date, the development standards of twins are as follows:
- The size of children at 11 weeks should be at least 43-48 mm. If one of them does not correspond to its embryonic age, you can suspect a missed pregnancy.
- At 12-13 weeks, embryos should reach a size of 60 mm and a weight of 8-9 g.
- By the second screening (17-18 weeks), the weight of each twin child should be around 350 g. The size and estimated weight of the babies may differ by 10-50 g. At this time, the limbs and internal organs should be clearly differentiated .
- By week 32, children should gain about 1.8-2 kg.
Sex determination during multiple pregnancy can be difficult if the babies are hiding one after another or are facing each other. How long does an ultrasound scan of twins show developmental pathologies? The second screening is a kind of transshipment point: if during it the doctor does not detect any birth defects, then with a 90% probability no problems in the development of children until their birth will already be identified.
Genetic analysis
It has been established that the risk of genetic pathologies during pregnancy with twins is almost three times higher than with singleton. And the probability of lesion of the neural tube is five times more likely if there are not one, but several babies in the womb.
That is why with any suspicion of a disease or pathology of the fetus, a woman can be sent for genetic analysis. The first thing prescribed is blood screening. There is now serious debate among doctors about the viability of this study. According to the latest data, out of 1765 children who were diagnosed with Down syndrome according to such a procedure, only in 26 cases it really was confirmed.
Amniocentesis can show a more complete picture: amniotic fluid or blood sampling from the umbilical cord through a puncture in the abdomen. Genetics are required to offer the expectant mother such an option, however, before agreeing, it should be remembered that the procedure is extremely traumatic and often leads to termination of pregnancy.
Twice as many examinations
Pregnancy is always a big burden on the mother's body, and in the case of multiple pregnancy, it is also double. That is why such babies are often born prematurely and at first are weaker than their peers from singleton pregnancies.
The future mothers of two children have the right to go on maternity leave two weeks earlier than their friends who are pregnant with one baby. Such women are under the close supervision of doctors. For example, in addition to three standard screenings, they may be assigned an additional ultrasound.
Doctors pay special attention to the condition of the woman's cardiovascular system, early diagnosis of gestosis and the detection of diabetes in pregnant women. Also, the expectant mother needs to take a vitamin-mineral complex and iron preparations.
Even with an uncomplicated course of multiple pregnancy, experts recommend that you go to the hospital three weeks before the PDD, and in the case of triplets - 4 weeks.
Easy pregnancy and childbirth!