When do you see twins on an ultrasound? Norms and terms of development, photo

2024 Author: Priscilla Miln | [email protected]. Last modified: 2023-12-16 00:21

Many women dream of having twins. This is such happiness: your child will never be alone, he will have someone to play with and chat with in the evening before going to bed. Seeing the cherished two strips on the test, many of them run to the doctor, cherishing the hope of hearing the cherished words. And the gynecologist hesitates and waits for something. When do you see twins on an ultrasound? And is everything so clear with multiple pregnancy?

fraternal twins

The phenomenon of twins still has no clear scientific interpretation. Of course, the mechanism for the birth of twins has already been well studied, but scientists still do not understand the factors that affect the development of multiple pregnancy without medical intervention.

In the case of heterozygous twins, a woman ovulates not one, but two eggs that fertilize two sperm. Doctors tend to attribute this to hormonal disruptions in the expectant mother's body, which can be triggered by hormonal contraceptives, stress or stimulation.

In someIn cases, the hereditary factor also plays a role: about 10% of women have a genetic predisposition to double ovulation. However, the reasons for it 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 ordinary brothers and sisters. Such twins can be seen on ultrasound when both embryos are already fixed in the uterus. Terms 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 one sperm. Everything goes according to plan until, under the influence of factors unknown to science, the zygote divides 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 pattern of these twins are still different. If the cell starts dividing late, or a genetic failure occurs during this process, then the probability of the birth of Siamese twins is high.

Such twins will not be immediately visible on ultrasound. However, by the first screening at 11-13 weeks, there is a high probability of finding two babies.

Where did the second one come from?

Ideally, the first ultrasound for a woman is done immediately after contacting the antenatal clinic: 1, 5-2 weeks after the delay of menstruation or at 5-6 obstetric weeks.

Thisnot a full-fledged screening, but a diagnostic procedure that allows you to determine the presence of an embryo in the uterine cavity. This early diagnosis helps rule out an ectopic pregnancy.

And now the first ultrasound shows one fixed egg, and the reassured and satisfied expectant mother sets off to get used to her new status. And the more her surprise will be when, after about a month and a half, at the first screening, the uzist will congratulate her on a multiple pregnancy. Where does the second baby come from?

Each woman's body is individual, and the week in which twins are seen on ultrasound depends entirely on the characteristics of the mother. The second embryo at the time of the first study may not yet reach the uterine cavity. After all, sometimes fertilization does not occur on the same day, but in world history there are cases when fraternal twins 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 either has not yet begun to divide, or its division is so small that no, even the most qualified, doctor can yet determine the presence of two babies.

Where did the other one go?

Most doctors, when asked when twins are seen on ultrasound, will name terms from 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 is this happening?

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 atearly terms, the cell may resolve or simply remain in the uterine cavity until delivery. In this case, on subsequent ultrasounds, the doctor will find a fetal egg, which does not pose any threat to either the mother or the second child.

Second Screening Surprise

However, the 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 the doctor can't see two babies before?

The presence of embryos in the uterus is determined by several signs: heartbeat, the presence of two amniotic sacs filled with amniotic fluid, and two placentas. Are twins immediately visible on an ultrasound?

Yes and no. When each of the children has its own placenta and bladder, and this is usually a variant of fraternal twins, it is not difficult to determine their presence.

With identical twins, development can go two different ways. Both babies have one placenta for two, but they can be located in one or two amniotic sacs.

If children are in the same bubble, then their visualization in the early stages is extremely difficult. Therefore, monochorionic monoamniotic twins are usually the 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 provinces, is assigned the first diagnostic ultrasound. Usually, doctors limit themselves to blood tests and manual examinations. Here are some indirectsigns by which the gynecologist may suspect twins and prescribe an additional examination:

• extremely high levels of hCG and ACE;
• severe anemia;
• womb size not appropriate for gestational age;
• early movements;
• presence of pathological toxicosis and fatigue;
• fast weight gain.

However, multiple pregnancy is not always accompanied by some special phenomena. Many women continue to feel good even when twins or twins are seen on an ultrasound.

Norms and terms of development

While expectant mothers are wondering if twins can be seen on ultrasound, doctors and scientists are conducting research, systematizing data and finding out how to determine the developmental pathologies of children from multiple pregnancies in the early stages.

Due to the presence of two children in the uterine cavity, visualization is often difficult. Despite modern equipment that allows for research in 4D format, when twins are clearly visible on ultrasound, determining the size, sex and weight of each individual fetus sometimes causes problems even for an experienced specialist.

Today, the norms for the development 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 miscarriage.
• At 12-13 weeks the embryos should be 60mm and weigh 8-9g
• By the second screening (17-18 weeks) weight of each twinshould be around 350 g. At the same time, the size and estimated weight of the babies may differ from each other by 10-50 g. At this time, the limbs and internal organs should already be clearly differentiated.
• By 32 weeks, babies should gain about 1.8-2 kg.

Sex determination in multiple pregnancies can be difficult if the babies are hiding one behind the other or are facing each other. At what time is the pathology of development visible on the ultrasound of twins? The second screening is a kind of staging post: if during it the doctor does not find any birth defects, then with a 90% probability, no problems in the development of children will be identified until they are born.

Genetic analysis

It has been established that the risk of genetic pathologies during pregnancy with twins is almost three times higher than with a singleton. And the likelihood of neural tube damage is five times more likely if there are more than one baby in the womb.

That is why, with any suspicion of illness or pathology of the fetus, a woman can be sent for genetic analysis. The first step is a blood screening. Now there is a 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 this procedure, only in 26 cases it was actually confirmed.

Amniocentesis can show a more complete picture: taking amniotic fluid or blood from the umbilical cord through a puncture in the abdomen. Geneticists are obligedoffer the expectant mother this option, but before agreeing, you should remember that the procedure is extremely traumatic and often leads to termination of pregnancy.

Twice as many surveys

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.

Expectant mothers of two children have the right to go on maternity leave two weeks earlier than their girlfriends who are pregnant with one baby. Such women are under the careful supervision of doctors. For example, in addition to the three standard screenings, they may be assigned an additional ultrasound.

Doctors pay special attention to the condition of a woman's cardiovascular system, early diagnosis of preeclampsia and detection of diabetes in pregnant women. Also, the expectant mother needs to take a vitamin-mineral complex and iron supplements.

Even with an uncomplicated multiple pregnancy, experts recommend going to the hospital three weeks before the due date, and in the case of triplets - 4 weeks before.

Easy pregnancy and childbirth for you!