First scan of pregnancy

What Every Mom-To-Be Needs to Know

Moms-to-be typically look forward to ultrasounds during pregnancy more than any other prenatal appointment. It’s easy to see why! It’s fun to get a sneak peek of your bundle of joy while your OBGYN looks for specific growth and development markers. Many women look forward to learning their baby’s sex as soon as possible and wait impatiently for their 20-week ultrasound. Others want to be surprised. Whether or not you intend to learn about your baby’s sex ASAP, it’s important to keep all your ultrasound appointments.

An ultrasound, also known as a sonogram, is typically performed by an ultrasound technician or sometimes by an OBGYN. It uses sound waves to create an image of the organs inside your body. (These sound waves are not harmful to you or your baby.) Ultrasounds during pregnancy help doctors diagnose many diseases and conditions, even those not related to pregnancy.

This article will cover why and how ultrasounds are used during your pregnancy, how many ultrasounds to expect while you’re pregnant, and what your OBGYN may be looking for at each ultrasound.

Most pregnant women typically only get two ultrasounds, one at the beginning of pregnancy and one about halfway through. Other women may have three or more ultrasounds done depending on a number of factors.

Your First Ultrasound

Your first ultrasound is called the “dating” or “viability” ultrasound. It’s typically done between 7 and 8 weeks to verify your due date, to look for a fetal heartbeat, and to measure the length of the baby from “crown to rump.”  At this ultrasound, you’ll also learn whether you’re having one baby, pregnant with twins, or more! You may even get to see or hear your baby’s heartbeat during this appointment.

If you have irregular periods, or didn’t have a period after coming off birth control, this ultrasound will be especially helpful in determining a more accurate due date. Your due date is important because it helps your doctor know whether your baby’s development is on track each month.

We’ll perform this ultrasound at our Madison Women’s Health clinic.

What to Expect at Your First Ultrasound

When you’re just 7 or 8 weeks pregnant, your fetus is only about two centimeters long. In order to get a close enough view of your uterus and fetus, the dating ultrasound is done transvaginally. This means the ultrasound is done internally, literally “through the vagina.”  A transvaginal ultrasound can be a little uncomfortable, but it is not painful. Most would say it feels less invasive than a gynecological exam that uses a speculum.

To perform this ultrasound, your OBGYN or ultrasound tech will gently insert a narrow ultrasound wand just inside your vagina. The transvaginal ultrasound wand is also called a transducer. It’s about three centimeters around, a little larger than a tampon. It will be covered by a condom and lubricant. The wand will not reach your cervix and is safe for your baby.

You may be asked to arrive at your first ultrasound with a full bladder. Having a fuller bladder helps to put your uterus in a better position for the ultrasound.

What Your Doctor is Looking for at Your First Ultrasound

• Viability of pregnancy
• Fetal heartbeat
• Fetal size
• Single or multiple pregnancy

Genetic Screening Ultrasound

If you choose to have prenatal genetic testing done, you’ll have your next ultrasound at 12 to 13 weeks gestation. This ultrasound is also called nuchal translucency screening. It’s offered to everyone and is covered by most insurance plans. This genetic screening ultrasound is optional.

During this ultrasound, your doctor will look for indicators of chromosomal disorders. Chromosomal disorders mean that the baby received an extra chromosome at conception and could have moderate to extreme physical or mental challenges. These disorders include:

• Trisomy 21, known as Down Syndrome
• Trisomy 13
• Trisomy 18

Read more about carrier screening and prenatal genetic testing. Also check out the article about at-home genetic testing kits.

What Your Doctor is Looking for at the Genetic Screening Ultrasound

This ultrasound will be an anatomical scan. Your doctor will look to see if all four limbs are present. They will also look for basic structures in the brain, the stomach, the bladder, the nasal bone, and last but not least, something called nuchal translucency. Nuchal translucency is a fluid sack at the back of the baby’s neck that is filled with lymphatic fluid. There are correlations between the size of that sack of fluid and the likelihood that the fetus could be affected by a major chromosomal disorder.

After the ultrasound has been performed, your OBGYN will interpret the results and share the information with you. You may also meet with a genetic counselor who could recommend having additional tests done to verify the ultrasound results.

Keep in mind that ultrasound screenings for other genetic disorders or anatomic abnormalities become more accurate further into the pregnancy.

We’ll perform this ultrasound at the Madison Women’s Health clinic.

Should you Get a Genetic Screening Ultrasound?

There’s no right or wrong answer to this question. Ultimately, the decision is up to you. Here are some good questions to ask yourself as you decide whether to have the genetic screening:

• Is there a family history of these genetic birth disorders?
• Would I terminate my pregnancy if there was a risk of Downs Syndrome, Trisomy 13, Trisomy 18, or other genetic disorder?
• Would knowing about my pregnancy’s risk of genetic defect make it easier to emotionally or physically prepare for a baby with a birth defect?
• Would it be easier for me to cope with and enjoy pregnancy if I focus on the more likely positive outcome rather than the chance of birth defects?

Whether you choose to have genetic screening done at this time is entirely your decision. Some women prefer to have as much information as possible as early as possible, while other women do not. If you’re still uncertain, you can discuss the pros and cons with your OBGYN.

Basic Anatomy Scan Ultrasound

This is the ultrasound that people look forward to the most! The full anatomy ultrasound is typically performed at about 20 weeks, or 5 months. As the name implies, this ultrasound will look at all the baby’s organ systems to make sure they’re present, are a normal size and shape, and are in the right location.

What to Expect at a Full Anatomy Scan Ultrasound

The full anatomy scan is a transabdominal ultrasound. It uses a transducer that looks a lot like a store checkout scanner. The ultrasound technician will put warm ultrasound gel on your stomach and then slide the transducer in the gel around your stomach. The gel helps the sound waves travel through your skin.

Tip: Come to your appointment with a relatively full bladder. This will make it easier for your ultrasound technician to get better images of your baby.

Because there are so many things to look for, this ultrasound will take at least 45 minutes—if your little one cooperates! If you’ve got an extra squirmy baby who is “camera shy,” it could take a few hours to get all the images that we need. Don’t worry, we have a lot of tricks to encourage your baby to change positions—everything from asking you to lay on one side and then the other, emptying your bladder or filling it, maybe even walking around. We’ll do whatever it takes to get the images we need to track your baby’s growth and development.

What Your OBGYN is Looking for at a Full Anatomy Scan

During the full anatomy, 20-week ultrasound, you can find out if your baby is male or female. If you want the sex to be a surprise, be sure to tell your technician know ahead of time so they don’t accidentally let it slip. When the scan is complete, Meriter will even send you a link to view some fun photos of your baby!

Your ultrasound technician will capture a large number images and measurements:

• limbs: arms, legs, feet, hands
• torso: chest, heart, kidneys, stomach, bladder, diaphragm, genitals
• head and face
• spine
• umbilical cord
• amount of amniotic fluid
• location, size, and shape of your placenta
• length of your cervix

After your ultrasound technician has captured all these images and measurements, your OBGYN will review the pictures and look for abnormalities such as congenital heart defects or cleft lip or palate. They’ll discuss their findings with you and help you understand what you’re looking at in the different images.

If everything looks normal and there are no other issues during your pregnancy, the next time you’ll see your baby is when he or she is in your arms! In the meantime, you can enjoy those 2D or 3D photos of your baby!

This ultrasound will be performed at UnityPoint Health – Meriter Hospital Center for Perinatal Care.

“Extra” Ultrasounds

Sometimes, women need additional ultrasounds during pregnancy. Your OBGYN may ask you to come in for additional ultrasounds to check your:

• Cervical length: if your cervix is shorter than expected, you may need to have your cervix checked regularly to be sure it stays closed so that you can maintain your pregnancy. If the cervix continues to shorten or thin, you may need a cerclage to help strengthen it until it’s time to deliver your baby. Cervical length ultrasounds occur at 16, 18, 20 and 22 weeks and are done transvaginally.
• Placental location and size: if your placenta is too small, if it is in an abnormal location or if it is an abnormal shape, then we will need to monitor it and the growth of your baby with regular ultrasounds. Your placenta is responsible for passing blood and nutrients to your baby, so it’s important thrat it is growing correctly.

You may need growth ultrasounds if you have:

• hypertension
• diabetes
• high BMI (body mass index) going into pregnancy
• preeclampsia
• indicators that your placenta or uterus is not growing appropriately

Sometimes, growth ultrasounds are needed to check that your baby’s growth is continuing along the growth curve. They’re done at 28, 32, and 36 weeks. One way doctors estimate whether your baby is growing as expected is by measuring your fundal height. Fundal height is the number of centimeters from your pubic bone to the top of your uterus. This measurement typically increases about 1 cm each week. If your uterus has not grown appropriately in the last month, your OBGYN will surmise that your baby is also not growing and will want to perform monthly growth ultrasounds.

What to Expect at a Growth Ultrasound

These ultrasounds take less time than the full basic anatomy ultrasound because there are fewer measurements required. The ultrasound technician will measure the baby’s head circumference, bi-parietal diameter, abdominal circumference, and femur length.

What Your OBGYN is Looking for at Growth Ultrasounds

Your OBGYN is looking to see if your baby is staying on its growth curve. We will also use the measurements to estimate your baby’s weight. A large or extra large baby isn’t typically concerning. An extra-small baby or a baby who does not grow according to their growth curve could mean that the baby is not getting enough nourishment through the placenta and may need to be delivered early.

2D, 3D, and 4D Ultrasounds

2D ultrasounds are the black and white images that you’re probably used to seeing. To an untrained eye, they can look pretty fuzzy or obscure. However, they give the best definition of the structures of your growing peanut and are considered the “gold standard” of diagnostic imaging.

3D images are especially popular among parents-to-be who want to enjoy those cute baby pictures even before the baby is born! These pictures show facial features and look much more baby-like than the kind of obscure 2D images. 3D ultrasounds have usefulness beyond the cuteness factor, however! In the case of abnormalities of the spine or palate, 3D ultrasounds can help your OBGYN get a better idea of the severity.

4D images are like a 3D image, but show the baby moving around. They’re like getting to see a live action video of your little one. These are less commonly done because they don’t actually help with diagnoses. Depending on which perinatal center you go to, you might receive a link to view your ultrasound images or videos online.

While there are some stand-alone ultrasound centers offering to tell you your baby’s sex early on or to give you keepsake 3D or 4D images, these aren’t necessary and are rarely covered by insurance. You’ll find out everything you need to know during your appointments at the perinatal center — and those appointments will be covered by your insurance.

The best place to have an ultrasound performed is always at a clinic, where you will have access to a physician who has been trained in interpreting the images. At Madison Women’s Health, we’re happy to print off pictures for you to put in your baby’s scrapbook — or anywhere else you’d like to display those “coming soon” photos.

Final Thoughts

Ultrasounds during pregnancy are a fascinating way to get a glimpse of your developing baby. Don’t be afraid to ask your OBGYN for more details about genetic screening as you determine whether that is something you want done. And make sure you’ve set aside a good amount of time for your ultrasounds — especially the all-important full anatomy scan!

—

Dr. Beth Wiedel has been providing healthcare to women in Madison since 2002 and is a founding partner of Madison Women’s Health.   She shares the vision of all the partners of being a strong healthcare advocate for her patients, emphasizing compassion and communication throughout her practice.

12-week scan - NHS

If you're pregnant in England you'll be offered an ultrasound scan at around 10 to 14 weeks of pregnancy. This is called the dating scan. It's used to see how far along in your pregnancy you are and check your baby's development. The scan may also be part of a screening test for Down's syndrome.

Your midwife or doctor will book you a dating scan appointment. It will usually take place at your local hospital ultrasound department. Most scans are carried out by sonographers.

You may need to have a full bladder for this scan, as this makes the ultrasound image clearer. You can ask your midwife or doctor before the scan if this is the case. The dating scan usually takes about 20 minutes.

Find out more about what happens during a pregnancy ultrasound scan

Credit:

Nic Cleave / Alamy Stock Photo https://www. alamy.com/stock-photo-12-twelve-week-ultrasound-scan-antenatal-photo-of-unborn-foetus-baby-18962836.html?pv=1&stamp=2&imageid=E0A8E3FE-D4B6-4EF5-9687-24C92C3FEA0F&p=74035&n=0&orientation=0&pn=1&searchtype=0&IsFromSearch=1&srch=foo%3dbar%26st%3d0%26pn%3d1%26ps%3d100%26sortby%3d2%26resultview%3dsortbyPopular%26npgs%3d0%26qt%3dB2RR84%26qt_raw%3dB2RR84%26lic%3d3%26mr%3d0%26pr%3d0%26ot%3d0%26creative%3d%26ag%3d0%26hc%3d0%26pc%3d%26blackwhite%3d%26cutout%3d%26tbar%3d1%26et%3d0x000000000000000000000%26vp%3d0%26loc%3d0%26imgt%3d0%26dtfr%3d%26dtto%3d%26size%3d0xFF%26archive%3d1%26groupid%3d%26pseudoid%3d788068%26a%3d%26cdid%3d%26cdsrt%3d%26name%3d%26qn%3d%26apalib%3d%26apalic%3d%26lightbox%3d%26gname%3d%26gtype%3d%26xstx%3d0%26simid%3d%26saveQry%3d%26editorial%3d1%26nu%3d%26t%3d%26edoptin%3d%26customgeoip%3d%26cap%3d1%26cbstore%3d1%26vd%3d0%26lb%3d%26fi%3d2%26edrf%3d0%26ispremium%3d1%26flip%3d0%26pl%3d

What is the purpose of the dating scan?

The purpose of the dating scan is to check:

• how many weeks pregnant you are and work out your due date (the estimated date of delivery, or EDD)
• whether you're expecting more than 1 baby
• that the baby is growing in the right place
• your baby's development

This scan can detect some health conditions, such as spina bifida.

Does screening for Down's syndrome happen at the dating scan?

This depends on whether you have agreed to have the screening and when the scan takes place. Screening for Down's syndrome will happen at the dating scan if:

• you have agreed to have screening for the condition
• the scan takes place between 10 and 14 weeks of pregnancy

The screening test for Down's syndrome used at this stage of pregnancy is called the combined test. It involves a blood test and measuring the fluid at the back of the baby's neck (nuchal translucency) with an ultrasound scan. This is sometimes called a nuchal translucency scan.

The nuchal translucency measurement can be taken during the dating scan. If you have agreed to have screening for Down's syndrome, the dating scan and the screening will usually happen at the same time.

Find out more about the screening for Down's syndrome, Edwards' syndrome and Patau's syndrome

You will not be offered the combined screening test if your dating scan happens after 14 weeks. Instead, you'll be offered another blood test between 14 and 20 weeks of pregnancy to screen for your chance of having a baby with Down's syndrome. This test is not quite as accurate as the combined test.

Find out more about: 

• the 20-week scan
• ultrasound scans in pregnancy
• GOV.UK: screening tests for you and your baby

Page last reviewed: 18 December 2020
Next review due: 18 December 2023

Prenatal ultrasound screening in the 1st trimester of pregnancy

Early prenatal screening is done in the first trimester. The purpose of the examination is to identify the risks of chromosomal abnormalities in the fetus, as well as to determine the risks of developing preeclampsia (a complication of pregnancy), fetal growth retardation, and premature birth.

What is early screening and why

Screening in early pregnancy is a set of studies consisting of:

• ultrasound diagnostic procedures;
• biochemical blood test.

Purpose of early screening:

• detect or rule out gross malformations;
• determine the risk group by the presence of chromosomal abnormalities.

The risk for chromosomal abnormalities is calculated for Down, Edwards and Patau syndromes. Chromosomal diseases are incurable and lead to severe developmental disorders of the fetus. Therefore, it is very important to diagnose such problems as early as possible. nine0003

When is the 1st trimester screening

Combined screening of the first trimester is carried out at 11-14 weeks of pregnancy (11 + 0 days - 13 + 6 days, where the important point is: the coccyx-parietal size of the fetus should be at least 45 mm and not more than 84 mm). The best time is the 12th week - the "golden mean". Since a biochemical blood test is more informative at 10-11 weeks compared to 13 weeks, and an ultrasound study is more clear and informative at 12-13 weeks, since the baby is larger and more mature. nine0003

What are the indications for early screening

Early prenatal screening is a routine examination, so all expectant mothers should pass it on time. It can be difficult to determine it on your own, so you need to register for pregnancy as early as possible. During the appointment, the obstetrician-gynecologist will determine the duration of your pregnancy, according to which the best time is selected to undergo the first ultrasound screening.

What ultrasound shows in early screening

• Number of fruits.
• Signs of gross malformations of the fetus.
• Markers of chromosomal abnormalities.
• Place of attachment of the placenta.
• Quantity and quality of amniotic fluid.
• Blood flow in the mother's uterine arteries.
• The length of the cervix.
• Whether there are neoplasms in the uterus and ovaries (such as tumors, cysts).
• The sex of the baby in the first trimester is not yet precisely determined, but the sex can be assumed. nine0010

An ultrasound doctor performs fetometry and examines the anatomy of the fetus. The doctor measures the CTE, the thickness of the collar space, the circumference of the head and abdomen, the pulsation index in the venous duct, evaluates the nasal bone and "intracranial" space. The obtained indicators are compared with the normative ones. As a result, the exact gestational age is determined (with an error of two to three days), the proportionality of the development of the fetus, the presence or absence of gross malformations, the presence or absence of node-markers of chromosomal pathology in the fetus. nine0003

Also, the first ultrasound screening during pregnancy is done in order to determine the state of the child's organs and systems, which have already developed well and can be viewed during screening. The features of the anatomical structure and function of the heart, stomach and other organs of the digestive tract, bladder, kidneys, limbs and cranium, spine, and nervous system are assessed.

What you can find out with a biochemical test

Expectant mother donates blood to assess the following indicators:

• concentration of free β-hCG subunit (human chorionic gonadotropin)
• the concentration of protein A associated with pregnancy (PAPP-A).

Based on the concentration of these indicators, the doctor makes the first conclusions about the risk of chromosomal abnormalities in the fetus.

The accuracy of biochemical analysis is about 65%.

Accuracy of combined screening (taking into account ultrasound markers and indicators of biochemical analysis) is up to 90%.

What to do if screening results are not very good

The study is carried out at an early stage specifically in order to distribute women into risk groups who require additional examination to clarify the diagnosis.

In the Fetal Medicine Center, you can get not only early prenatal screening of the 1st trimester, but also a genetics consultation and an additional examination.

After a thorough diagnosis, the doctor at the consultation will explain its results to the parents and tell about all the options for further action. nine0003

How to prepare for early prenatal screening

For 4-5 days before the ultrasound, it is recommended to exclude from the diet products that cause gas formation (carbonated drinks, sweets, legumes, etc.). It is also desirable to exclude sexual intercourse 2-3 days before the study.

Screening for congenital fetal diseases during pregnancy

Category: Reminders for the population .

Screening during pregnancy is a complex of examinations, which includes ultrasound and biochemical analysis of venous blood for hormones. As a rule, screening is carried out three times - in the first, second and third trimester.

Early detection of pathologies is very important. This makes it possible to start treating genetic diseases as early as possible and, if not completely cure them, then at least stop the symptoms as much as possible. If the doctor notices any abnormalities during the examination, the pregnancy is monitored especially carefully, which makes it possible to prevent the development of complications or premature birth. If the detected pathologies turn out to be too severe and incompatible with life, the doctor will refer the patient to terminate the pregnancy for medical reasons. nine0003

Pregnancy screening is harmless for both mother and baby. This is a fairly accurate study, although it should be clearly understood that it does not give a 100% guarantee. The accuracy of screening depends on many factors - the professionalism of the researchers, the woman's compliance with the rules for preparing for the examination, and other factors.

First pregnancy screening

The first screening during pregnancy is carried out between the 11th and 13th weeks. It makes no sense to undergo this examination earlier - before the 11th week of pregnancy, many indicators are practically indeterminate. nine0003

The study includes two medical tests - an ultrasound and a blood test.

ultrasound

With the help of ultrasound, the doctor determines the exact gestational age, evaluates the baby's physique, its dimensions (head circumference, limb length, height), the work of the heart muscle, the symmetry of the brain, the volume of amniotic fluid, the structure and size of the placenta, as well as the condition and tone of the uterus. For each of these parameters, there are normal indicators with which the doctor will compare the results. For an 11-13 week pregnancy, these rates are:

• KTP (coccygeal-parietal size, that is, the length of the fetus from the crown to the tailbone) is 43–65 mm. If this figure is more than normal, then the child will be large. A downward deviation indicates slow development (the reason for this state of affairs is often a hormonal imbalance or infectious diseases suffered by the expectant mother), genetic pathologies or fetal death (in this case, the heart will not be auscultated). However, this may also be due to a banal mistake in determining the timing of pregnancy. nine0010
• BDP (biparietal size, that is, the distance from the temple to the temple) - 17-24 mm. A high BDP means a large fetus, but only on the condition that all other indicators say the same. Otherwise, we can talk about a herniated brain or hydrocephalus. Low BDP indicates slow brain development.
• TVP (collar space thickness) - 1.6–1.7 mm. Deviation from this norm (TVP above 3 mm) is considered a sign of some severe chromosomal pathologies - Down syndrome, Edwards syndrome, etc. However, one should not panic ahead of time - no one will make such a serious diagnosis only on the basis of TVP. To confirm, you need to take a blood test for hormones and take a biopsy of the outer dense shell of the embryo for further research. nine0010

The length of the nasal bone is 2–4.2 mm. Too small a nose bone can indicate pathology or simply that the baby's nose will be snub-nosed. HR (heart rate) - 140-160 beats per minute. A small (up to 40 beats per minute) deviation in one direction or another is considered a variant of the norm.

The size of the chorion, amnion and yolk sac. The chorion is the outer shell of the fetus, which will eventually become the placenta. If it is located on the lower wall of the uterus, they speak of chorion previa. This is a potentially dangerous situation, fraught with miscarriage, and in this case, bed rest is recommended for the pregnant woman. nine0003

The amnion is the inner membrane that holds the amniotic fluid. The normal volume of amniotic fluid at 11–13 weeks is 50–100 ml.

The yolk sac is an embryonic organ that, in the first weeks of a fetus's life, plays the role of some internal organs that will be formed later. By the time of the first screening, the yolk sac should practically disappear (then the examination form will indicate “not visualized”). If its size is about 6 mm, then the fetus may have certain pathologies. nine0003

Cervix. Normally, its length by the time of the first screening is 35–40 mm. A shorter cervix means a risk of preterm labor.

Ultrasound is performed in two ways - transabdominal, in which the sensor of the ultrasound machine is located on the abdomen, and transvaginal, in which it is inserted into the vagina. Transvaginal ultrasound provides more complete and accurate information, but it is usually performed only in the first trimester. This method is usually used when examining overweight women, since the fat layer in the abdomen does not allow the fetus and uterus to be examined in detail. nine0003

It is necessary to properly prepare for an ultrasound. Before a transabdominal ultrasound, it is advised to drink about a liter of water so that the bladder is full at the time of the examination - then the uterus will shift slightly towards the abdomen and the picture will be clearer. With transvaginal ultrasound, the degree of fullness of the bladder does not matter, however, before the examination, it is better to go to the toilet - it will be more comfortable. Before the examination, you need to take a shower or freshen up with wet wipes. The accumulation of gases can distort the results of ultrasound, no matter what method it is carried out. Therefore, expectant mothers suffering from flatulence are advised the day before the examination to take remedies for flatulence and not eat anything that produces gas. nine0003

Blood test

Biochemical screening, also called a dual test, is done to determine the level of two hormones (hence the name) - free b-hCG and PAPP-A.

• b-hCG (human chorionic gonadotropin) begins to be produced from the first days of pregnancy. Its amount gradually increases until about the 9th week, and then begins to gradually decrease. On average, for a period of 11–13 weeks, 50,000–55,000 mIU / ml is considered the norm. An elevated level of hCG may indicate a multiple pregnancy, or, in the worst case, genetic pathologies of the fetus or the presence of diabetes in the mother. Reduced hCG is typical of miscarriage, ectopic pregnancy, fetal death, or certain malformations (Patau syndrome and Edwards syndrome). nine0010
• PAPP-A is an A-plasma protein. The content rate for a period of 11–13 weeks is 0.79–6.01 mU / l. Low PAPP-A is a sign of chromosomal pathologies such as Down syndrome and Edwards syndrome, fetal death and miscarriage, fetal malnutrition (underweight) and preeclampsia.
• A high PAPP-A is a sign of multiple pregnancies, large fetuses, or a low placenta.

In order for the blood test to give the most accurate information, it must be taken on an empty stomach, at least 8 hours after the last meal. 2-3 days before the analysis, you should refrain from fried, fatty, spicy, smoked foods, chocolate, nuts, seafood. It is also recommended not to have sexual intercourse. All this is not so significant, but it can affect the result in one way or another. nine0003

Second pregnancy screening

The second screening during pregnancy is carried out at 16-20 weeks. Like the first one, it consists of the same two stages - ultrasound and blood test.

ultrasound

This time, the doctor determines not only the size, but also the position of the fetus and its bone structure, the condition of the internal organs and the place of attachment of the umbilical cord, as well as the volume of amniotic fluid. Here are the approximate main indicators of the norm for a period of 16-20 weeks:

• BPR - 26–56 mm.
• DBK (length of the femur) - 13-38 mm.
• DPC (length of the humerus) - 13-36 mm.
• OG (head circumference) - 112-186 mm.

IAF (amniotic fluid index, that is, the volume of amniotic fluid) - 73-230 mm. Oligohydramnios can adversely affect the condition of the child's bone structure and the development of his nervous system.

Localization of the placenta. There is some risk only when the placenta is located on the anterior wall of the uterus - with such localization, detachment of the placenta is possible. nine0003

Umbilical cord. One of the most important parameters is the place of attachment of the umbilical cord. Marginal, split or sheath attachment is fraught with fetal hypoxia and difficulties during childbirth, often it becomes an indication for caesarean section. The umbilical cord is fed through 2 arteries and 1 vein, although sometimes only one artery is available. This can cause fetal hypoxia, heart disease, disorders in the child’s cardiovascular system, and cause a baby’s low body weight. However, if all other analyzes and examinations do not show deviations from the norm, you should not worry. nine0003

Cervix. The length of the cervix at this time should be 40–45 mm. A short cervix means a threatened miscarriage.

Visualization. Unsatisfactory visualization can be caused both by the peculiarities of the position of the fetus or the excess weight of the expectant mother, and by edema or hypertonicity of the uterus.

Blood test

As during the first screening, during the second, a blood test for b-hCG is taken, the level of free estriol and AFP is also checked. Here are the norms for their content at the 16th-20th weeks of pregnancy:

• b-hCG - 4.67-5-27 ng / ml.
• Free estriol is a hormone whose level can be used to judge the state of the placenta. The norm is 1.17–3.8 ng / ml. Elevated estriol is characteristic of multiple pregnancy or a large fetus. Reduced - for threatened miscarriage, placental insufficiency, anencephaly and Down's syndrome.
• AFP is a protein that is produced in the gastrointestinal tract of the fetus. Norm - 15-27 U / ml. A slightly lower AFP may mean that the gestational age was determined incorrectly (slightly underestimated). If the AFP is very low, the cause may be Edwards or Down syndrome, the threat of miscarriage or fetal death. High AFP is characteristic of neural tube pathologies, esophageal atresia, Meckel's syndrome. High AFP is also possible in women who have had an infectious disease during pregnancy. nine0010

Third pregnancy screening

The third screening during pregnancy is carried out at the 30th-43rd week. Based on the results of this screening, the doctor decides on the need for a caesarean section or the possibility of a natural birth. The basis of the third screening is the same ultrasound. Sometimes dopplerography is prescribed - a study of the work of blood vessels. Here are the approximate norms for a given gestational age:

ultrasound

The thickness of the placenta is 23.9–43.8. Too thin placenta is not a particularly dangerous deviation from the norm. The reason may be the miniature physique of a woman, her infectious diseases, hypertension.

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