Ultrasound at 12 weeks of gestation: fetal size and other features

At the 12th week of pregnancy, the first scheduled ultrasound is most often performed. It will be accompanied by additional research, including laboratory tests. During this period, doctors and future parents can get a lot of interesting information about the baby's health. How is the diagnosis at this stage of carrying a child and what are the parameters of the baby, we will tell in this material.

Objectives of the survey

Ultrasound examination at the end of the third month of pregnancy is an integral part of screening aimed at identifying the likelihood of possible genetic pathologies. Together with a blood test of a pregnant woman, this method of research provides informative data that allow you to calculate individual risks of the birth of a child with developmental defects.

A prenatal screening test is usually scheduled on one of the days in the period from 11 to 13 weeks. 12 weeks is the most optimal period for diagnosis, since on it the information content of all the indicators of interest to the doctor at this stage is as high as possible.

Ultrasound at this time allows:

to identify markers that indirectly indicate the likelihood of a child having Edwards, Turner, Down syndromes, Cornelia de Lange disease, Patau syndrome, neural tube abnormalities that lead to pathologies of brain development;
check the gestational age, determine the expected date of birth;
find out the features of a particular pregnancy - whether it is multiple or common, complicated or not;
find out how the fetus feels, evaluate its vital activity, size, compare them with the developmental norms inherent in a given period;
identify problems with the reproductive health of the mother, if any, - eliminate the threat of miscarriage, detachment of the ovum and other pathological conditions.

Method and preparation

Ultrasonography at 12 weeks is often referred to as a genetic ultrasound. The attitude towards him is appropriate. With excitement and trepidation, expectant mothers are waiting for the day of examination, since the word "screening" scares and raises a lot of fears. Anxiety is unnecessary, experts say, after all, this ultrasound has no peculiarities, in comparison with similar diagnostics at other periods. Everything will be simple, familiar and painless.

The results of ultrasound at this time can be negatively affected by the accumulation of intestinal gases, which "push back" the pelvic organs, squeeze them. Therefore, a couple of days before the screening test, you should not eat cabbage, legumes, carbonated water. A few hours before going to the doctor it is worth taking "Simethicone" or "Espumisan". These medications will help eliminate traces of intestinal gas and prepare for the examination.

An ultrasound scan at 12 weeks is done on the same day with a laboratory blood sampling from a vein, which is necessary to establish the level of hormones and proteins responsible for the normal development of the baby and the correct flow of gestation. On the results of this analysis, which is carried out by biochemical research food, bad habits of the mother, for example, smoking, can affect.

To get more reliable results, 2-3 days before the examination, doctors do not recommend a woman to eat fatty foods, smoked and fried foods with a lot of spices, as well as sweets.

On the day of the examination, you should come to the consultation on an empty stomach. Before undergoing this ultrasound, a woman is weighed, measures her height, informs the attending physician all the data about her previous illnesses, about her previous pregnancies and childbirth.

Ultrasound scanning at this time is carried out mainly by the transvaginal method, which is popularly called "internal ultrasound". There is no need to fill the bladder, the doctor can access the view through the vaginal wall, bypassing the bladder area. 12 weeks are considered the borderline period at which doctors can begin to use the transabdominal method for diagnostics - an external ultrasound, when the sensor is driven only over the woman's abdomen, receiving a picture through the anterior abdominal wall.

The choice of the method remains with the doctor., and many things can affect him, including the physique of the expectant mother herself. If a woman is overweight, there is a noticeable fat layer on her abdomen, then it is most likely that the doctor will choose the vaginal examination method. Skinny patients are more likely to undergo an abdominal ultrasound at this time. In some cases, the doctor can use both methods.

What can you find out?

At this time, the baby becomes very similar to a small person, he has arms and legs. The embryo's tail has completely fallen off. Fingers have separated on the hands and feet, the pads of the fingers are acquiring individual features this week - a unique pattern that is a print.

All internal organs of the crumbs are fully formed, many of them (kidneys, liver, intestines, pituitary gland, heart) have already begun to function. The fruit itself already weighs about 14-15 grams, its average growth is from 45 to 80 mm. The kid is very active, he has already learned how to use the handles, he can play with them with the umbilical cord or suck his finger. If an ultrasound diagnostician "catches" him during these activities, he will definitely show the expectant mother what her grown-up baby is capable of.

The baby has already formed the external genitals, and therefore, with a favorable location of the child, the doctor may already try to determine his gender. If twins or triplets live in the mother's tummy, the doctor will be able to examine and evaluate the parameters of each of the babies.

Not all of the above can be seen at 12 weeks using ultrasound, because not every consultation has a modern scanner with high resolution and detail.

But any apparatus at this time will show how the fetus is moving, the mother will be able to hear his heart beating, the size of the fetus can also be easily determined.

During the procedure, the doctor necessarily examines the probability of genetic pathologies by their characteristic markers (visual indications). In addition, he will give an opinion on the state of health of the mother and tell you what to do if there is a threat of miscarriage, although at this time, if it was, it usually disappears, the condition of the mother and the fetus is normalized, and the toxicosis begins to recede.

Decoding the results

It is impossible to judge whether a child has the likelihood of genetic pathologies, many of which are fatal, and the rest simply do not leave a chance for healing the little one, by the conclusion of an ultrasound scan at 12 weeks alone. Therefore, doctors are engaged in decoding the screening, comparing what the doctor saw on the scanner monitor and what the results of a biochemical study of the pregnant woman's blood showed.

Therefore, it is not worth expecting that after an ultrasound it will become known whether the baby is healthy. We'll have to wait until the lab tests are ready. After visiting the ultrasound diagnostics room, the woman will be given a study protocol, in which, using numbers and letter abbreviations, they will “encrypt” basic information about the development of pregnancy. Let's look together at what such abbreviations mean and what rates are characteristic of this week of gestation.

At the very beginning of the protocol, it is described in what way the study was carried out, and also the date of the first day of the last menstruation is indicated - it is on this that the obstetric term and date of birth are calculated. The following is a general picture of what the doctor saw. The number of fetuses in the uterus is indicated with a mandatory indication of whether they are viable, whether they have signs of heartbeat.

An important value that makes it possible to judge the duration of pregnancy and the pace of development of the baby is the size from the crown to the tip of the coccyx, the so-called coccygeal-parietal size, or CTE. This week its average values are presented below.

Table of CTE standards for the period of 11-12 weeks and 12-13 weeks:

The following describes fetal heartbeat. The abbreviation HR (heart rate) is supplemented by a number. It is this that indicates the speed with which the baby's heart beats. At this time, the average value of 162 beats per minute is considered normal. Any value between 150 and 175 beats should not be questionable.

If the doctor does not like the frequency, he believes that the heart of the crumbs is beating slowly, unevenly, irregularly, too often, he will definitely report it. If this has not been said, you should not "wind" yourself over trifles.

Next, the doctor moves on to the main part, for which screening is carried out - the study of markers of chromosomal pathologies. There are only two such signs on ultrasound in this period - the thickness of the collar space (TVP) and the nasal bones (it is good if they are visualized, even better if they can be measured).

The space between the skin and the muscular skeleton on the back of the neck in children with various genetic diseases noticeably thickens due to the accumulation of fluid in this area. For example, babies with Down syndrome tend to have a shortened neck.

TVP as an indicator is informative only for this period, after 14 weeks it is not determined and can no longer tell about anything. The nasal bones in children with a number of genetic pathologies are flattened, and therefore in a child with severe developmental abnormalities, they may be very small, or may be absent altogether. This marker can also indicate probable problems.

Collar thickness and nasal bone length at 12 weeks:

In a separate column description of the anatomy of the embryo (fetus). There will be no numbers, but only the signs "+" or "-", which means that the fetus has this organ or is absent. The doctor can also indicate "norm", "no peculiarities", "examined" or enter data on the identified pathology.

To fill out this part of the study protocol, the bones of the cranial vault, the main structures of the brain ("butterfly"), the spine, a 4-chamber section of the heart, the baby's abdominal wall, stomach, bladder, fetal stomach, intestines are examined for a 12-week period. Separately, the number of limbs is counted, if there are two hands and the same number of legs, the doctor will indicate that they have been examined and are normal.

Determined chorionic position - a young placenta that barely had time to form. It is determined on which wall of the uterus the "child's place" is fixed. Usually this is the posterior wall, but the presence of the chorion on the anterior wall should not frighten at all. The distance from the internal os to the chorion is measured and, based on this indicator, it is established whether the placentation is sufficient, low or there is presentation.

Necessarily measured the thickness of the placenta. Its abnormal growth can also indicate either fetal infection or genetic pathologies. Normal indicators for this period are from 14.5 to 15.5 mm.

An ultrasound diagnostician necessarily evaluates the condition of the uterus, appendages, ovaries, measures the length of the cervix and indicates if everything is normal, if there is a risk of termination of pregnancy.

Sex determination is not included in the mandatory screening parameters. If a woman wants to ask this question to the doctor, she will have to pay at the rate of the antenatal clinic for the provision of paid services (within 500 rubles). However, no doctor can guarantee the accuracy of sex determination at this time. There is too great a risk of confusing the genitals with the umbilical cord or limbs, not seeing or not distinguishing a boy from a girl, since they are still very similar.

Experienced doctors are able to see the gender. The accuracy of "prediction" in the first trimester is from 75 to 80%. More accurately, you can see the gender on the next scheduled ultrasound examination at 18-20 weeks.

Possible problems

As part of an ultrasound scan at 12 weeks, some inconsistencies and problems may be identified. The most common situations:

CTE is less than normal. The reasons for this deviation may lie in a later ovulation, that is, the fetus is younger than the doctor and the pregnant woman herself think. In this case, another ultrasound is prescribed, after 1.5-2 weeks. A significant deviation of this value from the existing average standards may indicate developmental problems, which may be the result of bad habits, malnutrition of a pregnant woman, as well as a deficiency of the hormone progesterone in her body. With a decrease in the coccygeal-parietal size, congenital pathologies of a genetic nature are not excluded. In this situation, more research is needed.

No or less nasal bones. The absence of nasal bones (aplasia) or their small size increase the risks of developing a baby with chromosomal abnormalities, however, the accuracy of ultrasound as a diagnostic method does not always allow one to judge the presence of pathology. The doctor may not see the spout due to outdated low-resolution hardware. In addition, a small nose can be a hereditary personality trait if one of the parents has a small "button" nose.

The results of a biochemical blood test, as well as a control ultrasound scan in a few weeks, will help to understand the reason.

TVP is more than normal. A slight excess of this value should not cause alarm. Experts consider it “critical” to exceed the size of the collar zone by 6-8 mm above the upper limit. In this case, the woman is referred for a consultation with a genetics specialist, additional invasive methods are prescribed - chorionic biopsy or amniocentesis, in order to identify pathology or refute suspicions with an accuracy of 99.9%. A significant excess of the parameter should be supported by changes in blood formulas, in particular, a high level of hCG and a reduced level of PAPP-A protein.

Low placentation, presentation. Of course, these conditions are quite dangerous from the point of view of the possibility of losing a pregnancy, but the predictions in most cases are positive, because the uterus grows every day, and along with the stretching of the walls of the uterus, the placenta also rises (at 12 weeks - the chorion). The woman is prescribed a sparing mode of labor, with presentation, bed rest can be shown. A woman is prescribed drugs that have a positive effect on vascular permeability (Actovegin, Curantil), as well as vitamin complexes developed specifically for expectant mothers.

Threatened interruption, retrochorial hematoma. With such problems of bearing, the results of ultrasound at this time only confirm the alarming symptoms that a woman experiences - it can be bloody or bloody discharge, as well as pain in the lower abdomen and in the lumbar region. In this case, the decision on treatment is made by an obstetrician-gynecologist, who either sends a woman to a hospital to maintain pregnancy, or gives recommendations for treatment at home, if the hematoma (detachment of the ovum) is not extensive.

In general, the forecasts are quite positive, and with all the doctor's prescriptions and careful attitude to themselves, 95% of women manage to maintain a pregnancy and give birth to a healthy and beautiful baby on time.

Research accuracy

In the final part of the protocol, during a screening ultrasound, a woman can read that the results of the study do not guarantee the birth of a healthy child. The question arises - why then undergo screening if there is no clarity? The fact is that ultrasound is not considered an absolutely accurate method, the error and correction "for error" is from 10 to 15%.Thus, the accuracy of ultrasound at this time is about 90%... When determining the sex of a baby at 12 weeks, the accuracy is lower - 75-80%.

Ultrasound diagnostics at this time does not aim to establish specific diagnoses for mom or baby. Diagnostics only contributes to an overall assessment of the risks of a given woman having a sick toddler, and also allows you to monitor the pace of development of a tiny person. Apart from the results of blood biochemistry, the conclusion of an ultrasound scan is not considered and cannot speak of the presence of a sick baby in a woman.

Common questions

Both before and after the examination procedure, a large number of pregnant women have many questions. The answers to the most common ones are presented below:

Sex by heart rate. Popular rumor ascribes a rarer heartbeat to male fetuses than to girls. It is believed that future little princesses have their hearts beating often, “fearfully”, while in boys, the rhythm of the heart is measured, clear. From the point of view of medicine, it is impossible to argue that different sexes have different heart rates. This indicator is not divided by gender. However, experienced obstetricians in ancient times, when ultrasound was not available, this was how the sex of the unborn child was determined, however, they were mistaken in about 50% of cases.

Some differences in the tone and rhythm of heartbeats do occur, but at the very late stages of pregnancy. At 12 weeks, it is not worth judging the child's sex by the speed of the little heart.

3D ultrasound. The three-dimensional image, more familiar to the non-professional gaze of the patient, attracts and attracts every expectant mother. I'd like to look at my baby "in all its glory." But 12 weeks is too little time for such a study. The optimal time for 3D ultrasound is considered to be from 20 weeks and more. But even on a regular ultrasound scan, which takes place in the first trimester, you can ask to give pictures of a baby that no longer looks like a pea pod or an incomprehensible spot, but already quite humanly.

Ultrasound pictures. These pictures can rightfully be considered the first photograph of your child. If the picture is successful, then in the picture you can see the profile of the baby, his arms, neck, tummy and head, legs and even the umbilical cord. Most of the questions arise on the recognition of sexual characteristics in such "photos". With boys, everything is a little easier, while the slightly swollen external genitals of a girl are very easy to mistake for a boy.

If the doctor assumes that you have a girl, ask him to take a "photo" in this projection. If the location of the fruit allows this, then there will be less doubt.

Twins... In the ultrasound picture of twins, one baby is always visible better than the other. It is uncommon, but it is possible that one baby is hiding behind another, and the doctor may mistakenly conclude that a woman is carrying only one fetus. A close examination of the heartbeats should indicate that two hearts are beating. And subsequent ultrasound examinations show grown twins or twins for sure.