Jay Goldberg (Obstetrician/Gynecologist, Cedars-Sinai Medical Center) gives expert video advice on: What are "prenatal diagnostic tests"?; Am I required to have prenatal diagnostic tests while I am pregnant?; What are the chances of having a child with a birth defect? and more...
What are "prenatal diagnostic tests"?
Well there's a lot of testing that's done throughout a pregnancy. We typically have a generic panel of blood that we draw when a patient comes into the office and they're newly pregnant. They include things like checking for anaemia, checking a thyroid value, checking for hepatitis, HIV, syphilis, and rubella, which is German measles. It's always important to know your blood type, whether you're RH-positive or RH-negative. Nowadays, most offices are adding additional genetic screenings; for the Askanazi Jewish population there's a host of things. For most ethnically diverse groups, we're actually offering cystic fibrosis testing. Fragile X is a chromosomal abnormality with the X chromosome; it is frequently being tested now. In the African-American population we test for sickle-cell. In the Greek and some Asian populations we check for thalassaemia. So, there are a host of tests that will be consulted with your physician when you first arrive at the office. Throughout the pregnancy there are also other tests that will be performed. Some are invasive, dependent on screening test results that you have or on your age. Some are screening tests that are offered to everybody but of course they're optional. Then we test later in the pregnancy for certain vaginal cultures, we test for gestational diabetes which is diabetes unique to pregnancy. Each doctor will have a different game plan but there's a standard of care in the community that will be adhered to.
Am I required to have prenatal diagnostic tests while I am pregnant?
To my knowledge, none of these tests are mandatory. These are all optional tests. Now, there are definite tests that you would want to have performed. You would want to know if you're a hepatitis carrier, or HIV carrier. You'd want to know your blood type, because these things can help your pregnancy. If we were to find out you were HIV positive, we would then obviously treat you and safely try and deliver a baby who may be free of HIV. If you have an Rh-negative blood type, then you might need medication administered at some point during the pregnancy that would decrease the risk of there being complications with this pregnancy or future pregnancies. So, testing is optional, but should be discussed with your physician so you understand what you're refusing if you're refusing something.
What are the chances of having a child with a birth defect?
Well the chances of having a child with a birth defect varies from population to population based on your genetics, based on your age. So for specific statistics it is best to probably find out exactly when you're pregnant, how old you are and maybe some genetic counseling and then consult your physician.
What is an "ultrasound exam"?
An ultrasound is simply a probe or a device handheld by either a physician or a technician. It either can be placed in the vagina; called a vaginal ultrasound; or on the abdomen; called an abdominal ultrasound. It emits sound waves that bounce back to a receiver that then produces an image on the monitor, the screen; and it will bounce back bright, for hard things like bone, or metal; and it'll bounce back dark for fluid; like a cyst on the ovary, or fluid in the amniotic sac. Grey tends to be tissue, like the uterus or an ovary and so, with experience, a technician or an obstetrician can do an ultrasound, perform an ultrasound, and is able to emit images that they can then tell you how far along your pregnancy you are, fluid around the baby, complications with cysts or fibroids, many other hosts of things.
When is an ultrasound exam given during pregnancy?
Most doctors perform about three ultrasounds in the course of the pregnancy. The first ultrasound exam is typically done in the initial visit where the doctor will measure the baby's length to determine how far along in the pregnancy you are. Typically about the midpoint in the pregnancy, around 20 weeks, another ultrasound exam is preformed, often by a periontologist but not always, where they will look at the baby from head to toe and determine if the baby's anatomy is developing structurally normally. And then sometimes a physician will perform an ultrasound exam toward the end of the pregnancy to give an estimate of the baby's foetal weight or possibly to check the fluid around the baby, check for movements and position and breathing and all these sorts of things. Now that's a typical situation, but many doctors perform ultrasound exams throughout the pregnancy. Or, if you're having complications, like you were involved in a motor vehicle accident or the baby is not moving as much, then the doctor may opt to do an ultrasound exam to make sure everything is okay.
What are the risks of an ultrasound exam?
There are no known risks to an ultrasound exam. It's simply soundwaves that are being pushed into the uterus and emitted backwards. So there are no known risks. There are some controversial studies that have come out but none that have been solidified, none that have been truly believed to cause problems. So at this point, my answer is there's no known risks to an ultrasound.
What is an "amniocentesis"?
An Amniocentesis is an invasive test in which a long needle is placed into the abdominal cavity with ultrasound guidance some one will be performing an ultrasound allowing the person performing the test to see where there're going. The goal is to have the needle enter the amniotic sac, where there's a pocket of fluid, not a danger to the baby. Then remove approximately 1 to 2 CCs or milliliters of this fluid that can be then sent and analyzed for various things like the chromosomes of the baby or the baby's while risk of having neural tube defect.
When would an amniocentesis be given during pregnancy?
Typically an amniocentesis is given between about 16 and 18 weeks. Now, that's not a hard number or hard time schedule, because if an abnormality was detected at 22 weeks, an amniocentesis can be preformed at 22 weeks. An amniocentesis is also performed later in the pregnancy to document the baby's lung maturity. The true definition of amniocentesis is the entry of a needle into the abdominal sac. It can be performed later in the pregnancy. If a woman is threatening delivery but the doctor is concerned that she may be too premature, you can determine with an amniocentesis if the lungs of the baby are more likely to be mature or ready to breathe on their own, and then deliver this patient safely before her due date.
When should I consider additional prenatal tests?
You should consult your physician, because based on your ethnicity, and based on your religious affiliation, these things are going to possibly affect what prenatal tests are offered to you. So there are some standard tests that are offered throughout a pregnancy, but there are some additional ones that are offered based on who you are, and that's where you need to consult your physician in regards to prenatal tests.
What do I do if my prenatal test results are abnormal?
If your prenatal test results are abnormal, you definitely need to discuss the results with your physician. And hopefully your physician will discuss your abnormal prenatal test results with you before you start consulting the Internet. I think that there are a lot of things that can be abnormal on prenatal testing, but it doesn't always mean there is something wrong. A lot of these prenatal tests are screening tests, which mean that your baby may be at higher risks of having an abnormality, but it does not mean the baby has an abnormality. Further testing may need to be done after an abnormal prenatal test.