Prenatal Diagnosis Center Screenings

First Trimester Screening

11 - 14 Week Fetal Exam

20 - 22 Week Fetal Exam

Amniocentisis

Prenatal Ultrasound

 

First Trimester Screening

is a test consisting of an ultrasound examination and a blood test which can provide you with a risk estimate of having a child with Down syndrome and other chromosome abnormalities that is more accurate than Maternal AGE alone. 

The information posted below is an overview of the First Trimester nuchal translucency test. It is not intended to be a comprehensive review of all pertinent information. Your genetic counselor will explain the testing procedure in much more detail and answer all your questions.


1. What can First Trimester screening tell me about my pregnancy?
The screening determines what is the probability that the baby might have Down syndrome, or trisomy 13. This probability, or chance, is based on three criteria: your age, information obtained on a sonogram (ultrasound), and bloodwork. Your genetic counselor will discuss the results in more detail and answer all your questions.

2. How is First Trimester Screening performed?
This screening requires a sonogram and maternal blood work performed between 11 1/7 – 13 6/7 weeks of pregnancy. The sonogram will confirm how far along your pregnancy is. In addition, a measurement of the collection of fluid at the back of the baby's neck, called the nuchal translucency (NT), will be taken. Several other observations will be made including the presence of the nasal bone (see photo to the left), bladder length and the number of vessels in the umbilical cord. A maternal blood sample is also offered and used to analyze two chemicals called free beta-human chorionic gonadotropin (hCG) and pregnancy associated plasma protein-A (PAPP-A), which are found in the blood of all pregnant women. In some pregnancies when the baby has Down syndrome or trisomy 18, there is extra fluid behind the baby's neck and the hCG and PAPP-A results are higher or lower than average. Combining your age-related risk with the NT measurement and blood work provides you with a revised risk figure for Down syndrome and a risk figure for trisomy 18.

3. How accurate is First Trimester Screening?
Because this is a screening test, a positive result (showing an increased risk) does not mean that your baby has a problem, only that further diagnostic tests are options for you to consider. Also, a negative or normal result (one that shows a decreased risk) does not mean that the baby will not have Down syndrome or trisomy 18. The First Trimester screen detects about 95% of pregnancies in which the baby has Down syndrome or trisomy 18. A nuchal translucency sonogram can be performed without measuring hCG and PAPP-A; however, the detection rate of Down syndrome and trisomy 18 is reduced to about 85%. Finally, this screen is not designed to provide information about the possibility of other chromosome conditions, nor about many other genetic syndromes, genetic disorders, birth defects, or causes of mental retardation.

4. Should I still have the second trimester screening (triple or quad screen)?
The second trimester maternal serum screening test, also known as the "triple screen" or "quad screen", is performed between 16-22 weeks. Both of these screens measure chemicals in the mother's blood. Like the First Trimester screening, results from a second trimester "triple screen" or "quad screen" can be used to statistically adjust a woman's age-related risk for Down syndrome and trisomy 18. In addition, the AFP portion of the screencan identify pregnancies at an increased risk for open neural tube defects such as spina bifida, which First Trimester screening does not include. While these screens are certainly used as  additional screening options after having the First Trimester screening, interpretation of the results of the second test in light of the first is complex. Currently most laboratories do not combine results from First Trimester and second trimester screening into one overall adjusted risk figure.

5. What is the cost of First Trimester Screening?
The screening involves a charge for the ultrasound examination and the blood test. The blood test, may not be covered by your insurance and you may want to check with your insurance company to see if your specific plan will cover the cost of it. If they do not cover it, we maybe able to arrange a special discount. As with any service, if your insurance company requires pre-authorization, you are responsible for obtaining it from your OB or primary care physician prior to the appointment.

6. How will I receive my First Trimester Screening results?
The results based on Mothers age, the previous genetic history and the ultrasound will be discussed immediately after the examination. If you also have the blood test, the composite results will usually be available in 3-5 days.

We will receive these results from NTD Laboratories and will contact you and your primary physician with your results.

7. What if the screening shows an increased risk for one of the conditions?
If the screening results indicate that your baby is at an increased risk for either Down syndrome or trisomy 18, this does NOT mean that your baby necessarily has one of these conditions. A genetic counselor is available to go over your result and to discuss additional testing options such as chorionic villus sampling (CVS) and amniocentesis. CVS and amniocentesis are diagnostic tests that can tell you with greater than 99% accuracy whether or not a baby has a chromosome abnormality, such as Down syndrome or trisomy 18. Also, extra fluid behind the baby's neck (a larger than expected nuchal translucency) is known to be associated with other birth defects like congenital heart defects, skeletal defects and other genetic syndromes.

8. How do I schedule an appointment for First Trimester Screening?
Your obstetrician's office can give you more information about scheduling this screen at our office. You may also call us directly at 434-220-8620.Please make sure to check with your insurance company regarding coverage for this exam. As with any sonogram, you will not need to have a full bladder.

 

11-14 Week Fetal Exam

Why have a scan at 11-14 weeks?

Nuchal Translucency:
Currently the most accurate non invasive test for detecting Down syndrome during pregnancy is the measurement of the nuchal translucency with ultrasound between 11-14 weeks of pregnancy. (See First Trimester Screening)

What is the Nuchal Translucency?
The nuchal translucency is a collection of fluid beneath the fetal skin in the region of the fetal neck and is present in all fetuses in early pregnancy. The fluid collection is however increased in many fetuses with Down syndrome and some other chromosomal abnormalities. It is called a "translucency" because on ultrasound it appears as a black space beneath the fetal skin. It is this black space that you will see measured during the ultrasound scan.

If the Nuchal Translucency is increased what happens next? If the nuchal translucency is increased then you will be offered a test called amniocentesis. This test involves removing fluid from around the baby and examining the baby's chromosomes. In some circumstances an urgent report is requested and if sufficient cells are present in the sample the results may be processed as early as 2-3 days using a technique called FISH analyis. The complete analysis (long term culture) takes 7 to 10 days.

How is the Ultrasound Performed?
Most often, the exam can be performed trans-abdominally. If the resolution is poor or the fetus is not in position for an accurate measurement, a vaginal ultrasound may have to be done.  With this approach greater detail is obtained of the fetal anatomy.

What happens if the chromosome test (Amniocentesis) is normal?
For patients where there was an increased nuchal translucency and later a normal amniocentesis result, there is still a slight increased risk of a structural abnormality in the baby (6%, compared to the background risk of 2-3%); eg a congenital heart defect. For this reason a detailed ultrasound examination of the fetal anatomy is required and can be done from 18-20 weeks. A specialized exam of the fetal heart (echocardiography) is also performed at 22 weeks. For most patients the anatomy is normal and the pregnancy progresses uneventfully.

What happens to the increased nuchal translucency with advancing pregnancy?
In the majority of patients this disappears and is not visible at the routine 22 week ultrasound. This explains why it is important that the scan be performed around 11-14 weeks. This is a narrow window of opportunity to screen the baby for chromosome abnormalities.

What is the risk of the scan?
A transvaginal and transabdominal ultrasound examination is a safe investigation at all stages of pregnancy.

What else can the 11-14 week ultrasound scan show?
A scan at 11-14 weeks provides an opportunity to assess the anatomy of the baby. At this early stage of pregnancy it is now possible to determine many structural abnormalities previously only visible at 22 weeks. During the examination many parts the fetal anatomy will be pointed out to you. It is also an opportunity to determine the number of babies present and the baby's heart rate.

 

Routine 20-22 Week Ultrasound & Examination (22 week ultrasound)

This examination is expected to detect the majority of major fetal malformations. It is important to appreciate however that such an examination does not detect all abnormalities. Many congenital heart abnormalities are complex and escape diagnosis at the 22 weeks ultrasound examination. Also in many instances the view of the fetus may he hampered by the it's position at the time of examination. Also, the tissue interposed between the ultrasound probe and the baby absorbs the ultrasound waves, so if a particular patient is overweight the fatty tissue of the abdominal wall may make visualization of the fetus difficult. In these circumstances the patient may be rescheduled for further assessment of the fetus later in pregnancy when the fetus is slightly larger.

Finally in certain circumstances fetal abnormalities may not be evident on ultrasound despite adequate views. This may be explained by the natural history of the condition where the abnormality only becomes evident in later pregnancy or where there are in fact no structural changes in the baby (eg. cerebral palsy, biochemical abnormalities genetic disorders and some chromosomal abnormalities)

In the state of Virginia a routine ultrasound examination is offered to most patients between 20 and 22 weeks, and is loosely referred to as the "22 week ultrasound". The purpose of this examination is to:

  • To determine the viability of the pregnancy.
  • To determine the number of gestational sacs ie. singleton, twins , triplets and higher multiples.
  • To determine the gestational age of the pregnancy. Several measurements are taken of the baby including the head size, the abdominal circumference and the femur and humerus lengths.
  • Examine the baby for ultrasound findings suggestive of chromosomal abnormalities. For Down Syndrome such findings include absence of the nasal bone, thickened skin on the back of the neck, calcifications within the heart, dilation of the kidneys, abnormally bright bowel, and short arms and legs, Heart Defects and Upper Intestinal Obstruction..
  • To assess the overall fetal anatomy. This involves a detailed examination of the fetal head ,brain, face, lips, heart, stomach, lungs, abdominal wall, kidneys, bladder, spine arms, legs, hands, and feet. Several landmarks within individual organ systems are noted and recorded on video film for archiving. Only upon request is fetal gender disclosed (assuming it can be seen).
  • Assessment of the position of the placenta.
  • Assessment of the amniotic fluid volume.
  • Assessment of the pelvic anatomy and the cervix.

 

 

Amniocentesis

What is Amniocentesis?
Amniocentesis is a procedure which involves passing a fine needle through the maternal abdomen and the uterine wall into the amniotic fluid around the fetus in order to obtain a sample of the amniotic fluid. From this fluid, fetal cells are harvested, cultured and treated to reveal their chromosomes. While an amniocentesis can be performed at any stage in pregnancy, it is usually performed between 14-16 weeks. The volume of fluid aspirated is about 1/6th of that present around the fetus and this is naturally replaced over the next 24 hours.

Who may be offered Amniocentesis?
Amniocentesis is generally offered to patients who a) are 35yrs and over at the estimated date of delivery, b) to women who have previously had a child with a chromosomal abnormality, c) patients who themselves have a chromosomal abnormality or other rare metabolic or genetic abnormalities and d) occasionally to mothers who are extremely anxious regarding the possibility of a chromosomal abnormality in their baby.

How is it performed?
An ultrasound examination is first performed to a) confirm the dates, b) to determine the position of the placenta (afterbirth), and c) assess the baby for ultrasound signs of chromosomal abnormality such as Down Syndrome. A point on the abdominal wall is selected by the operator using ultrasound. It is then cleaned with an antiseptic. The amniocentesis needle is then guided into the amniotic fluid (the fluid surrounding the baby) by tracking it's course on the ultrasound screen. It takes about 30 seconds to draw up the straw colored fluid.

What are the risks of the test?
The principle hazard of the procedure is the risk of introducing infection into the pregnancy which may result in miscarriage. This complication occurs in only 1/500 tests performed. The warning signs of miscarriage include regular crampy period-like pains with fresh red bleeding which occur in the first 24-48 hours after the test. A small fluid leak is a rare problem with much less likelihood of progressing to pregnancy loss, this usually settles of its own accord. Because the procedure is performed with ultrasound guidance, fetal injury with the needle is extremely rare.

What happens to the specimen taken?
A 15-22ml sample of fluid is aspirated and dispatched to the laboratory. The baby's cells are extracted from the fluid and placed in a culture medium in a warm incubator. In 7-10 days when sufficient cells have grown, they are treated so the chromosomes are revealed. The chromosomes are examined under the microscope with ultraviolet light. Each individual chromosome pair (of which there are 23) are examined in detail. The laboratory scientist will examine the cells for an extra chromosome no. 21 (Down syndrome) and for any abnormality in the other 22 pairs of chromosomes.

What is to be expected after the test?
Most patients will experience a few crampy pains or some mild crampy abdominal discomfort after the test. This is due to irritation of the uterus by the amniocentesis needle.  If the pains worsen then contact your doctor. Some spotting after the test is also not unusual, but should this progress to fresh red bleeding then contact your doctor. Many patients will experience no symptoms after the test. Take it easy for the rest of the day although there is no need for bed rest. It is probably a good idea for someone to take you home after the test. You may resume normal activity about 24-48 hours after the test.

7. How long before I know the results?
Depending on the rate of cell growth in the incubator results are available in 10-12 days. You will be contacted by phone with the result and a written report will also be mailed directly to your doctor.

8. Are the results accurate?
A chromosome result is one of the most reliable medical tests which has an accuracy in the order of 99.9%.

What do I do following the procedure?
It is recommended that you have someone with you to drive you home. You should rest for approximately 48 hours after the procedure as you may experience some mild period type abdominal pains. For any other problems you should communicate with your own doctor.

Diagrammatic representation of an amniocentesis.

The patient's head is to the left and the legs to the right.

The needle is advanced into the largest pocket of fluid and 15-22 ml aspirated. It takes 5-10 minutes to set up the procedure and 1-2 minutes to aspirate the fluid. Sometimes the fetus may move in the way of the needle but this does not it cause any harm.

 

Pelvic or Gynecologic Ultrasound

Are there other than pregnancy reasons for women to have an ultrasound?

Ultrasound examinations can help determine the causes of pelvic pain, abnormal bleeding, or other menstrual problems. Ultrasound images can also help to identify palpable masses such as ovarian cystsand uterine fibroids, as well as ovarian or uterinecancers. Sonohysterography (saline infusion sonography) is a relatively new procedure in which sterile saline is injected into the uterus while atransvaginal sonogram is performed. The purpose is to distend the uterine cavity (endometrial cavity) to look for polyps, fibroids, or cancer, especially in patients with abnormal uterine bleeding. Other indications include evaluation of the uterine cavity looking for uterine anomalies (abnormal uterine shapes since birth) or scars. The saline outlines the lesion and allows for easy visualization and measurement. Some physicians also use sonohysterography for patients with infertility. Saline and air are injected into the uterus and the physician looks for air bubbles passing through the fallopian tubes, which would indicate patency of the fallopian tubes.

How should I prepare for the procedure?

A full bladder helps with visualization of the uterus, ovaries and bladder wall. For transvaginalexaminations, no bladder filling is required.

What does the equipment look like?

The equipment consists of a transducer and a monitoring system. The transducer is a small, hand-held device that resembles a microphone. The radiologist orsonographer spreads a lubricating gel on the patient’s lower abdomen, where the uterus and ovaries are located, and then presses this device firmly against the skin. Transvaginal ultrasound uses a wand-like device that is covered, lubricated and inserted into the vaginal canal.

The ultrasound image is immediately visible on a nearby screen that looks much like a computer or television monitor. The radiologist or sonographer watches this screen during an examination and captures representative images for storage. Often, the patient is able to see the monitor as well.

An example of the ultrasound equipment that may be used is shown at the top of this page.

How does the procedure work?

Ultrasound imaging is based on the same principles as the sonar used by bats, ships at sea, and anglers with fish detectors. As a controlled sound wave bounces against objects, its reflected waves can be used to identify how far away the object is, how large it is, its shape and its internal consistency (fluid, solid or mixed).

The ultrasound transducer functions as both a loudspeaker (to transmit the sounds) and a microphone (to record them). When the transducer is pressed against the skin, it directs a stream of inaudible, high-frequency sound waves into the body. As the sound waves echo back from the body’s fluids and tissues, the sensitive microphone in the transducer records the strength and character of the reflected waves. With Doppler ultrasound, the microphone captures and records tiny changes in the sound wave's pitch and direction. These signature waves are instantly measured and displayed by a computer, which in turn creates a real-time dynamic picture on the monitor. The live images of the examination can be recorded on videotape or on a disk. In addition, still frames of the moving picture are usually "frozen" to capture a series of images. These "frozen" images are used to obtain measurements and to document the essential positions of the examination.

Doppler ultrasonography is an application of diagnostic ultrasound to detect moving blood cells in vessels and measure their direction and speed of movement. The Doppler effect is used to evaluate movement by measuring changes in the frequency of the echoes reflected from moving structures.

How is the procedure performed?

For the transabdominal approach, a clear gel is applied to the lower abdomen to help the transducer make secure contact with the skin. The sound waves produced by the transducer cannot penetrate air, so the gel helps to eliminate air pockets between the transducer and the skin. The sonographerthen presses the transducer firmly against the skin and sweeps it back and forth to image the pelvic organs. Below is an example of a transabdominal transducer.

Transvaginal ultrasound involves the insertion of the transducer into thevagina after the patient empties her bladder and is performed very much like a gynecologic exam. The tip of the transducer is smaller than the standardspeculum used when performing a Pap test. A protective cover is placed over the transducer, lubricated with a small amount of gel, and then inserted into the vagina. Only two to three inches of the transducer end are inserted into the vagina. The images are obtained from different orientations to get the best views of the uterus and ovaries. Doppler sonography can be performed through the transvaginal transducer, which is the same transducer used during sonohysterography. Below is an example of a transvaginal transducer (probe). Transvaginal ultrasound is usually performed with the patient lying on her back and with her feet in stirrups as during a gynecologic exam.

Each method has its advantages. The transabdominal approach offers an expanded view of the entire pelvis, showing where one internal structure is in relation to another. Since the transducer is brought closer to the area being examined in the transvaginal and transrectal approaches, improved visualization may be achieved. Thus, it can be helpful in locating the embryonic heartbeat in an early pregnancy, evaluating the uterine texture, or measuring a cyst in an ovary. Your physician will decide whether one or a combination of approaches is best for your particular case.

What will I experience during the procedure?

Ultrasound imaging of the pelvis should be painless. With transabdominalultrasound, you will lie on your back on an examining table. The sonographerwill spread some gel on your skin and then press the transducer firmly against your body, moving it until the desired images are captured. There may be varying degrees of discomfort from pressure as the transducer is moved over your abdomen, especially if you are required to have a full bladder.

With transvaginal ultrasound, although the examination is often performed to look for a cause of pelvic pain, the sonogram itself should not be painful or significantly increase your discomfort. A vaginal sonogram is usually more comfortable than a manual gynecologic examination.

Almost all examinations take less than 30 minutes.

What are the benefits vs. risks?

Benefits:

  • Ultrasound imaging is a noninvasive (no needles or injections, in most cases), usually painless examination.
  • Pelvic ultrasound can help to identify and evaluate a variety of urinary and reproductive system disorders in both sexes, without even the minimal risks associated with x-rayexposure.
  • Ultrasound provides real-time imaging, making it a good tool for guiding minimallyinvasive procedures, such as needle biopsies.

Risks:

What are the limitations of Pelvic Ultrasound Imaging?

Ultrasound waves are reflected by air or gas. Therefore, ultrasound is not an ideal imaging exam for the bowel. Barium exams and CT scanning may be the methods of choice for bowel-related problems.

Ultrasound has difficulty penetrating bone and can only see the outer surface of bony structures and not what lies within and beyond. For visualizing bone or internal structure of certain joints, other imaging modalities, such as MRI(magnetic resonance imaging), may be selected.


 

 


Who should consider prenatal testing and genetic counseling?

  • You are pregnant and will be 35 years of age or older on your due date.
  • You are pregnant with an abnormal expanded AFP blood test. (Quad Test)
  • You have had an ultrasound of your fetus showing a possible birth defect.
  • You have already had a child or close relative with a birth defect or genetic disease.
  • You and your partner are carriers of a recessively inherited disease such as Tay-Sachs, sickle cell anemia, cystic fibrosis or thalassemia.
  • You are a carrier of an X linked disease such as Fragile X, hemophilia or muscular dystrophy.
  • You and your partner are closely related to each other (such as first cousins).
  • You have been exposed to medications, X-rays or other agents during your pregnancy that may be harmful to the developing fetus.

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Doctors

Siva Thiagarajah , MD
Medical Director of PDC
Fotini Vavelidis, MS, CGC
Genetic Counselor
>>About our Staff

What We Do

High Risk pregnancy management
Ultrasound

Genetic Counseling
Early screening for abnormalities

Contact

Appointments: 434-220- 8620
Fax: 434-220-8625
info@prenataldiagnosiscenter.com

600 Peter Jefferson Pkwy Suite 190
Charlottesville, VA 22911