Level II ultrasound

Level II Scan

also known as

Anatomy, Anomaly or Targeted scan

ULTRASOUND EXAMINATIONS
baby inside



  

Level II - anomaly, targeted or dating scan

  
At the second trimester scan they check that your baby is developing normally, they assess the gestational age by measuring the crown-rump length and will also look for any major problems. This is a routine ultrasound examination performed at 18 to 20 weeks of gestation.

During the examination, the fetus is seen by abdominal ultrasound. The fetus is now large enough for an accurate survey of the fetal anatomy. With multiple pregnancies, they can be firmly diagnosed and dates and growth can also be assessed. Placental position is also determined. Further scans may be necessary if abnormalities are suspected.

Most parents look forward to their scans because it gives them an early glimpse of their baby. Most, will probably be given a printout of their baby by the sonographer as a keepsake, it is important to remember the main purpose of the scan.

The ultrasound scan, is not to provide the first photo for your baby album, or to find out your baby's sex. It is to check that your baby is growing and developing normally.


What is Level II  |  What is examined at this scan?  |  Triple test, Blood Tests
 
  Examples of ultrasonography you may see used during your pregnancy.


  
Ultrasound information :-    Who, Why, When?
What happens during an ultrasound examination?
Can the scan show the gender of my baby?
 




  

What is the Level II ultrasound?

  
ultrasoundIts origins are in the early days of ultrasound where a more detailed ultrasound examination was performed to explain the abnormal results of a screening blood test, called the Triple Test or MSAFP Blood Test. To explain some of those results, a 'Level II' study was performed.

Physicians still use the term 'Level II' because it is a convenient short-hand way of communicating to and among pregnant women, even though the purpose of the 'Level II' has changed.

A scan is performed at 18 to 20 weeks when the fetus is large enough for an accurate survey of the fetal anatomy, and when dates and growth can also be assessed. After your baby's heartbeat is checked, the main purpose of this scan is to check your baby's anatomy for normality. A thorough examination of your baby's brain, heart, spine, kidneys, organs and limbs will be undertaken. The placenta will be checked for its position, and measurements of your baby will be performed to ensure it is growing normally. Further scans may be necessary if abnormalities are suspected.

Level II scans are also known by other names like, dating, anomaly or targeted scan.
 

  

What is examined at this scan?

  
This is a detailed scan during which each part of the fetal body is examined. After checking your baby's heartbeat a thorough examination of your baby's brain, heart, spine, kidneys, organs and limbs will be undertaken. The placenta will be checked for its position and measurements of your baby will be performed to ensure it is growing normally.

CRLThe following measurements are usually made:

The Crown-rump length (CRL)

The length of the embryo on the longest axis constitutes the crown-rump length. This is among the best documented parameters to date the embryo, with accuracy of +/- 3 to 5 days. As a rough rule of thumb, the CRL + 6.5 = Menstrual Age in Weeks. An important point to note is that when the due date has been set by an accurately measured CRL, it should not be changed by a subsequent scan.

For example, if another scan done 6 or 8 weeks later says that one should have a new due date which is further away, one should not normally change the date but should rather interpret the finding as that the baby is not growing at the expected rate.

BPDThe Biparietal diameter (BPD) and head circumference (HC)

The diameter between the 2 sides of the head. This is measured after 13 weeks. It increases from about 2.4 cm at 13 weeks to about 9.5 cm at term. Different babies of the same weight can have different head size, therefore dating in the later part of pregnancy is generally considered unreliable. Dating using the BPD should be done as early as is feasible.

femurThe Femur length (FL)

The femur, or thigh bone, is the white structure located near the top of the image. Its length is measured from one end to the other [white +]. Measurement of the longest bone in the body reflects the longitudinal growth of the fetus. Its usefulness is similar to the BPD. It increases from about 1.5 cm at 14 weeks to about 7.8 cm at term. Similar to the BPD, dating using the FL should be done as early as is feasible.

Abdominal circumferenceThe Abdominal circumference (AC)

The abdominal circumference is shown by the white dots surrounding the structure in the middle of the image. The stomach is the black area located top left of the circle. The single most important measurement to make in late pregnancy. It reflects more of fetal size and weight rather than age. Measurements are useful in monitoring growth of the fetus.
AC measurements should not be used for dating a fetus.

Fetus Estimated Weight and Due Date

The weight of the fetus at any gestation can also be estimated with some accuracy using polynomial equations containing the BPD, FL, and AC. computer softwares and lookup charts are readily available. For example, a BPD of 90mm and an AC of 310m will give a weight estimate of 2.7 kg (6lb).

It is common to make at least 2 measurements to estimate gestational age. In most cases, BPD, Head Circumference or Femur length are used. Since all of these measurements are strongly related to gestational age, it is not usually important how they are combined. Most modern ultrasound machines include computerized biometric analysis programs used to easily calculate your Estimated Due Date or EDD or EDC.

Measurement Standards  |  Measurement = Weeks Gestation Calculator

Charts: Crown-Rump Length  |  BPD - OFD - HC
Femur and Humerus  |  Abdominal circumference  |  Fetal Weight


fetus spineSpine and abdominal wall
The sonographer will check your baby's spine in both the long view and in cross section, moving through the neck and shoulders to the pelvis. He is making sure that all the vertebrae are in alignment, that the skin covers the spine at the back and the baby's abdominal wall covers all the internal organs at the front.

Kidneys and bladder
The two kidneys are either side of the spine, below the stomach and are usually quite hard to see. If the baby's bladder is full, it's easy to see as a black bubble in the pelvis.

fetal heartHeart and stomach
They will look at the heart. The top two chambers, or 'atria', and the bottom two chambers, or 'ventricles', should be equal in size and the valves should open and close with each heartbeat. They will then look beneath the diaphragm to see the stomach, under the heart on the left side. Your baby swallows some of the amniotic fluid that it lies in; this can be seen in the stomach as a black bubble.

Long bones, hands and feet
ultrasound arm ultrasound handultrasound footThe long bones of the arms and legs, also the position of hands and feet are examined; the fingers and toes are looked at.



Placenta, umbilical cord and amniotic fluid
The placenta may be on the front or the back wall of your womb, usually near the top (or fundus) so may be described as 'fundal' on your scan report. Many are described as 'low' because they reach down to or cover the neck of the womb (cervix). If your placenta is low, another scan will be arranged in the third trimester, by which time most placenta will have moved away from the cervix.

It is possible to count the three vessels in the umbilical cord but this may not be done routinely. There should be enough amniotic fluid surrounding the baby to allow it to move freely at this stage.

Embryonic Heart Rate (EHR)
Since the advent of sonography, and specifically endovaginal sonography, a window on the developing human embryo and fetus has been opened that was not available before.

It is known that the normal embryonic heart rate (EHR) accelerates until the 9th menstrual week. The heart rate in the early pregnancy has a characteristic acceleration phase, peak rate of 175 B/M (+/-20, 2SD) at approximately 9.2 weeks, followed by a deceleration until approximately 15-17 weeks. After the deceleration phase the heart rate then becomes relatively constant after 16 weeks at about 145 B/M (+/-25), with a very slight negative slope, until term.

  1. The heart rate accelerates at 3.3 B/M during the first month of beating from around the start of the 5th LMP week until 9.2 weeks.
  2. The above acceleration is approximately 10 B/M every 3 days.
  3. The acceleration rate is approximately 100 B/M during the first month of beating.
  4. If the embryonic age calculated from the EHR is >7 days less than the age by CRL, there appears to be an increased likelihood of first trimester failure or anomalies.
    This difference in age is calculated as: CRL age - EHR age = 7 or more days.
Factors that can interfere with your EHR test and the accuracy of the results include:
  • Nicotine (such as from cigarette smoking) and large amounts of caffeine (such as from several cups of strong coffee), which can falsely raise your baby's heart rate and produce inaccurate test results.
  • Extra noises such as your heartbeat or your stomach rumbling.
  • If your baby is sleeping during a nonstress test.
  • Fetal movement during the test. If your baby is moving a lot, it may be difficult to correctly position the external montioring device.
  • Being overweight, or pregnant with multiple babies. In these cases it may be difficult to correctly position the external monitoring device.
 

  

Second Trimester biochemistry (blood test)
Cordocentesis Triple Screen or Quad Screen

  
Also known as:   Triple test, AFP Maternal, msAFP, Quad Screen, 4-marker screen
A blood test which is carried out between 15 and 20 weeks of pregnancy.
The tests measure various 'markers' in your blood:
    Triple Screen:
  • AFP (alpha-fetoprotein)
  • hCG (human chorionic gonadotropin)
  • uE3 (unconjugated estriol)
    Quadruple Screen:
  • same as above with the addition of inhibin A
To assess the risk of carrying a fetus with abnormalities, such as Down syndrome (trisomy 21), Edward's syndrome (trisomy 18), and open neural tube defects during the second trimester.
 




  

How many scans should I have?

 
As a practical matter, ultrasound scanning has proven to be so popular with patients and also their obstetricians, that almost everyone receiving regular prenatal care ends up with at least one scan anyway. The total number of scans will vary depending on whether a previous scan has detected certain abnormalities that require follow-up assessment.

There is no hard and fast rule for the number of scans you should have during pregnancy.

In some countries, sonograms are performed just twice during pregnancy. Once at 16 - 18 weeks to assess fetal abnormalities, and again at 32 - 34 weeks to assess age and well-being.

It is now recommended that all pregnant women have a dating scan in the first trimester - ideally at 10 to 13 weeks of pregnancy - to confirm your dates. This is especially important if you are going to have any screening tests for Down's syndrome, as knowing the exact dates makes sure your result is accurate. Most hospitals offer a scan in the second trimester at about 20 weeks (the anomaly scan) to check that your baby is developing normally.
 

  

Related articles

  
Week by week scan pictures:   First Trimester   |   Fetus Growth Measurement Charts

Examples of ultrasonography you may see used during your pregnancy.
 

  

Week By Week Pregnancy Progress Calendar

 
First Trimester
Week 1   Week 2   Week 3   Week 4   Week 5   Week 6   Week 7  
Week 8   Week 9   Week 10   Week 11   Week 12   Week 13
Second Trimester
Week 14   Week 15   Week 16   Week 17   Week 18   Week 19   Week 20  
Week 21   Week 22   Week 23   Week 24   Week 25   Week 26
Third Trimester
Week 27   Week 28   Week 29   Week 30   Week 31   Week 32   Week 33  
Week 34   Week 35   Week 36   Week 37   Week 38   Week 39   Week 40
 




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