Prenatal Ultrasound and Amniocentesis Testing
Ultrasound
The First Trimester Screen (with Nuchal translucency evaluation) is a non-invasive evaluation that combines a blood test (drawn on the mother at approximately 11 weeks) with a very specialized ultrasound of the back of your baby’s neck between 11-14 weeks’ gestation to identify your level of risk for having a baby with Down syndrome (Trisomy 21) or Edwards Syndrome (Trisomy 18). Approximately 90% of babies with Down syndrome and 95% of babies with Trisomy 18 will be identified as being at “increased risk” based on this combined test. A “positive” test does not mean that your baby has Down syndrome or Trisomy 18, but rather that there is an increased risk of these disorders (for example, greater than 1 in 100) and that you are eligible for additional counseling and testing if you so desire. This program is sponsored by the State Prenatal Screening Program. Once you are enrolled, if your test is positive (based on the blood test and ultrasound combined), the State will pay for additional testing (including any or all of the following: genetic counseling, one additional ultrasound, and amniocentesis if you desire).
The technique for Nuchal Translucency assessment is very specific and requires special training, expertise, and certification. At OC maternal-Fetal Medicine, we are specifically certified to provide this service, and we are also certified by the State Prenatal Screening Program to provide all follow-up services as needed if the screening test is positive.
Additionally, if you so request, we are usually able to determine the gender of your baby at the time of the 1st trimester ultrasound (as early as 12 weeks’ gestation). While this initial determination is preliminary (don’t paint the walls yet!), it is generally correct in approximately 90% of cases or more. Presuming that return for a second trimester ultrasound, the gender will be able to be confirmed with virtually 100% accuracy.
Of all the tests you will undergo during your pregnancy, the Second Trimester Comprehensive Ultrasound is clearly one of the most important because it is the best opportunity to assure that your baby’s anatomy and organ development is proceeding normally as expected. Of course, it is also a wonderful time to see the first views of your baby’s appearance and confirm the gender. Our desire is that the ultrasound of your baby will be a joyful, reassuring experience. We provide information during and after your ultrasound so that you will know everything there is to know about the results of your exam while you are still in the office. We always provide plenty of pictures of your baby to remember the experience (as well as complementary 3D/4D views of your baby in most cases).
One of the advantages of having your ultrasound performed at OC Maternal-Fetal Medicine is that we are certified by the American Institute of Ultrasound in Medicine as specialty providers of this service. Additionally, Dr. Kurtzman personally evaluates every baby. He is Board Certified in Obstetrics and Gynecology as well as a Maternal-Fetal Medicine (Perinatology) and has also completed additional fellowship training in Obstetrical Ultrasound. Fortunately, most ultrasounds are completely normal. However, even in patients with no high-risk factors, there is a 2-4% baseline frequency of major and minor fetal structural abnormalities (anomalies). Our state-of-the-art high-resolution ultrasound machines and our specific expertise in obstetrical ultrasound allow us to perform the highest level of comprehensive ultrasound examination of your baby.
OC Maternal-Fetal Medicine is accredited by the American Institute of Ultrasound in Medicine.
Along with comprehensive first and second trimester ultrasound, we provide ultrasound in the late stages of pregnancy as well. These ultrasounds are generally performed to assess fetal growth, amniotic fluid volume, and placental function to assure the ongoing well-being of your baby as you approach your due date. Additionally, our state of the art machines are equipped with the best 3D/4D imaging available for both diagnostic and enjoyment purposes (which we will provide as a courtesy to you during your otherwise medically-indicated exam)
Amniocentesis
An amniocentesis is a diagnostic test which provides definitive genetic information about your baby. For example, if you have a condition which places you at an increased risk for having a child with a genetic disorder (such as Down Syndrome), an amniocentesis will provide a definitive yes or no answer as to whether the baby is affected.
During an amniocentesis, a small amount of amniotic fluid is removed from the sac surrounding the baby and tested. The sample of fluid (less than one ounce) is removed through a very thin needle inserted into the uterus through the abdomen, and the fluid is replaced naturally within 24 hours. The procedure is performed using ultrasound guidance so that the exact position of the needle may be followed throughout the procedure. The fluid is then sent to a laboratory for analysis.
Different tests can be performed on a sample of amniotic fluid, depending on the genetic risk and indication for the test. Any patient may undergo amniocentesis if she so desires. The procedure is ideally performed between 16-18 weeks’ gestation (though it may be performed any time after 15 weeks’ gestation and as late as the third trimester in certain circumstances). The risk of miscarriage following an amniocentesis varies in different studies. It is generally cited to be around 1 in 300 procedures, though in our experience, the risk of pregnancy loss is approximately 1 in 1000 procedures or less. Most patients tell us that the procedure is less uncomfortable than they anticipated, and the level of discomfort is comparable to what you might expect when having your blood drawn.
The most common conditions for which a patient may be offered an amniocentesis would include the following:
- The patient has a fetal abnormality diagnosed at the time of an ultrasound
- The patient is going to be 35 years old or older at the time of delivery
- The patient has family history of certain birth defects or genetic disorders (such as cystic fibrosis).
- The patient has previously had a child with a birth defect.
- The patient has a “positive” 1st or 2nd trimester screen through the California State Prenatal Screening program
- The patient has a desire, for one reason or another, to know for certain the genetic composition of the baby (even if the screening tests are otherwise normal)