Diagnostic Testing for Maternal-Fetal Medicine
Modern prenatal diagnosis is a collaborative effort, often involving specialists from a number of different areas of medicine. At the Fetal-Maternal Center, you will have access to specialists from virtually every field of maternal, fetal, genetic, neonatal and surgical care.
We may recommend one or more tests or procedures to help care for you and your baby. Some of these include:
Three-Dimensional (3D) Ultrasound
One of the first steps in your evaluation is a complete ultrasound examination by a Maternal-Fetal Medicine specialist. Ultrasound uses sound waves to create an image on a television screen for your doctor and you to see. It is very important to know the number of fetuses, fetal size, weight and gestational age, location of the placenta, appearance of the cervix, amount of amniotic fluid and any abnormalities of the uterus or ovaries.
We will look closely at your baby's heart, face, brain, stomach, spine, kidneys, bladder, arms, legs, hands, feet, umbilical cord and gender. Ultrasound also allows us to examine the baby's liver, spleen, adrenal glands, intestines and lungs along with blood flow in various blood vessels. Specialized three-dimensional (3D) and four-dimensional (4D) imaging is used as well. Depending upon the complexity, the examination may take up to an hour. Usually, you will be able to watch the entire examination on a separate television screen.
If a problem is suspected, your doctor will explain the findings to you and make specific recommendations. Further tests might be needed, such as amniocentesis, blood tests or magnetic resonance imaging (MRI). You may need to see a specialist in cardiology, cardiovascular surgery, general surgery, plastic surgery, orthopedic surgery, urology, genetics, neonatology or fetal surgery. During your visit with us, our care coordinator will work with you to arrange all additional tests and appointments that might be required.
Inside the uterus, amniotic fluid surrounds and protects your baby. The main source of amniotic fluid is fetal urine. By analyzing a small sample of amniotic fluid, we can learn many things. For example, amniotic fluid studies can detect conditions such as Down syndrome, trisomy 18, trisomy 13 and other genetic abnormalities. Your doctor and genetic counselor will explain the conditions that can and cannot be detected using amniotic fluid.
Amniotic fluid is removed from the uterus by a procedure called amniocentesis. Your doctor will use ultrasound to identify an appropriate pocket of amniotic fluid inside the uterus. Then, under sterile conditions, a very fine needle will be inserted into the amniotic fluid and about 20 milliliters (four teaspoons) of amniotic fluid will be removed with a syringe. The needle is then removed. The procedure usually lasts about 30 seconds and your doctor will use ultrasound throughout the procedure to ensure safety. The amniotic fluid is then sent to the lab for testing.
In most cases, you will be able to resume your normal activities the next day. The 20 milliliters of amniotic fluid that are removed account for no more than two to four percent of the total fluid in the uterus and your baby will replenish it within a day. If your blood type is Rh negative, we will recommend that you have a RhoGam injection before leaving the office.
Chorionic Villus Sampling
Chorionic villus sampling (CVS) is a prenatal test that involves taking a small sample of tissue from the placenta, a structure in the uterus that provides blood and nutrients from the mother to the fetus, to test for chromosome abnormalities, such as Down syndrome and many others, and certain other genetic problems. Before having the test done, your genetic counselor and doctor will explain the conditions that can and cannot be detected using this test.
The chorionic villi are tiny projections of placental tissue that look like fingers and contain the same genetic material as the fetus. Testing may be available for other genetic disorders, depending on the family history and availability of lab testing at the time of the procedure.
CVS is usually performed at about 11 weeks of pregnancy. Unlike amniocentesis (another type of prenatal test), CVS does not provide information on neural tube defects, such as spina bifida. For this reason, women who undergo CVS also need a follow-up blood test called a maternal serum alpha-fetoprotein (AFP) level between 16 to 18 weeks of their pregnancy to screen for neural tube defects. It is also a good idea for them to have a detailed ultrasound at about 18 weeks to look at the spine of the fetus in particular for the same reason.
In our center, transcervical CVS is performed. This is a procedure in which a catheter is inserted through the cervix into the placenta to obtain the tissue sample. Removing the small amount of tissue does not affect the fetus's ability to get the blood supply it needs from the placenta.
A fetal echocardiogram is a very detailed evaluation of your baby's heart by a specialist in fetal echocardiography who is trained to use ultrasound to study the structure of your baby's heart.
Sometimes routine ultrasounds detect abnormal fetal heart rhythms, fetal heart abnormalities or abnormalities of another major organ system. If one of these abnormalities or other risk factors is detected, your physician may recommend a fetal echocardiogram. Pregnant women who are at increased risk of giving birth to a baby with congenital heart disease should have a detailed fetal echocardiogram performed by a physician who is specially trained in fetal cardiac evaluation.
The detection of a heart defect increases the risk of finding other malformations in the child. A detailed ultrasound of the rest of the fetus is necessary. Also, amniocentesis to test the chromosomes may be recommended.
Echocardiograms present no known risks to the mother or the fetus.
Fetal Magnetic Resonance Imaging (MRI)
In some cases, additional imaging studies are needed to help clarify the ultrasound findings. A fetal MRI (magnetic resonance imaging) scan is a special exam to look inside your body without using X-rays. Radio waves, a magnet and a computer are used to create two-dimensional (2D) or three-dimensional (3D) images of your body and your baby. If your doctor believes that a fetal MRI will provide additional useful information, our care coordinator will make arrangements for you to have the study performed at Children's Hospital Los Angeles.
The MRI scanner is a large square machine with a hole in the middle, resembling a square donut. During the MRI scan, you will be positioned on your back on a sliding table. The table will slide your entire body, feet first, into the scanner, which is like a tunnel open on both ends.
To the best of our knowledge, MRI is not believed to be hazardous to the fetus. Nevertheless, an MRI will be recommended only if your doctor believes it will provide additional information that will help us care for you and your baby.
Often, women see a genetic counselor before having an ultrasound examination and other services at our center. Genetic counselors are health professionals with specialized graduate degrees and experience in the areas of medical genetics and counseling.
They work as members of a health care team with the geneticist, perinatologist and others, providing information and support to families who have members with birth defects or genetic disorders and to families who may be at risk for a variety of inherited conditions. They identify families at risk, investigate the problem present in the family, interpret information about the disorder, analyze inheritance patterns and risks of recurrence and review available options with the family.
Genetic counselors frequently speak with patients about complex scientific and emotional topics. Usually the issues involve genetic conditions or birth defects or possibilities of those things occurring. The reason you are seeing the counselor and the perinatologist will usually be the main subject of counseling. For example, a common reason to come to our center is for advanced maternal age, defined as being 35 years old or older at the time the baby is expected. Often, the genetic counselor acts as an interpreter for the medical information and as a support person if the information turns out to be stressful.
Your genetic counselor asks extensive questions about your family history, as this is the way we understand inheritance patterns. It might be helpful for you to use the opportunity of a pending genetic counseling visit to research the health and medical conditions of extended relatives. Genetic counselors also provide supportive counseling to families, serve as patient advocates and refer individuals and families to support services.
When the patient has a very complex problem, such as an abnormal ultrasound result, or when a patient needs to be medically evaluated because she has a suspected genetic disorder herself, a clinical geneticist will see the patient. A clinical geneticist is a doctor who specializes in genetics. The geneticist also supervises the genetic counselors and reviews the counseling they provide for quality assurance.
A Specialized Ultrasound Examination is similar to a standard ultrasound exam, but with a higher level of detail and attention paid to the baby's anatomy. A Specialized Ultrasound allows the physician to look at the fetus from head to toe, checking for any irregularities in structure and anatomy, while assessing the baby's growth and environment, including the placenta, umbilical cord and the amniotic fluid. The scanner, or ultrasound machine, allows the physician to visualize the fetus in real time by supplying a continuous picture derived from the measurement and interpretation of high frequency sound waves bounced off internal structures. The type of image depends upon the density of the structure, from bone to fluid. These sound waves cannot be heard by anyone, including the fetus. The sound waves are emitted from a transducer placed on the abdomen. The ultrasound beams project a picture on a screen, from which the anatomy is viewed and measurements can be taken.
A Specialized Ultrasound utilizes sophisticated imaging equipment and technology, offering a range of options and views for the most complete evaluation possible. There are many reasons that a specialized ultrasound might be recommended, including a questionable finding on a standard ultrasound exam, family history of a problem that might be detected by ultrasound, maternal age, medical conditions such as diabetes, or a test result from routine blood work that requires further evaluation. Ultrasound examinations are performed by a perinatologist with expertise and experience in ultrasonography as well as training and certification in maternal and fetal medicine, including diagnosis and management of problems that might be encountered. Having a specialized ultrasound does not mean that there is necessarily anything wrong. It is a means to get more information and to be assured that all is well, or if not, that the proper care is available to ensure the best outcome.
What Is Looked at in a Specialized Ultrasound?
A specialized ultrasound begins with an overall view of the fetus, including position, placental location and measurements of the head, abdomen and extremities. These measurements are helpful in establishing gestational age and evaluating growth and development. Next, detailed examination of the fetal anatomy includes multiple views of the organs and structures, often utilizing three-dimensional (3D) or four-dimensional (4D) imaging technology, Doppler velocimetry, color-flow Doppler and color power angiography. Function is assessed as well as structure. A specialized ultrasound includes evaluation of the fetal skeletal system, circulatory system, spine, brain, face, heart, lungs, diaphragm, liver, stomach, adrenal glands, kidneys, intestines, bladder, gender, extremities, umbilical cord, placenta and amniotic fluid as well as the uterus and surrounding organs.
What to Expect
You will be asked to recline on an exam table, on your back to start, with your abdomen exposed. There is generally no need to undress, as moving clothing out of the way is sufficient to allow the transducer the access needed. There may be a wait between the time you are placed in the room and the time the physician arrives. The physician will place some gel on your abdomen. The gel is needed for the transducer to make the best contact with your skin, and to transmit the sound waves. The lights will be turned out, and a video screen will be available for you to view the ultrasound as it progresses. Structures will be pointed out, and views of your baby's face, hands and feet will be seen. You may be asked to turn on your side if that improves visualization. In some instances, a transvaginal ultrasound may be necessary to obtain the most accurate views of the baby, the placenta or the cervix. A specialized ultrasound may take as long as 30 to 60 minutes. Be sure to tell the staff if you need anything during that time.