Your doctor/midwife may have referred you to the Antenatal Testing Unit for a targeted ultrasound. This is performed using state of the art equipment and interpreted by individuals who specialize in ultrasound imaging. Common reasons for Targeted (Level II) Ultrasound include previous or family history of birth defects, abnormal serum screening (AFP, triple or quadruple Screen Testing), advanced maternal age, medication usage during pregnancy, or concerns over the results of an ultrasound performed in your doctor's office.
A targeted ultrasound, or Level II ultrasound examination provides a greater assessment of fetal anatomy, using top of the line ultrasound equipment and performed by specialists in prenatal diagnosis. This is recommended for women with personal or family histories of birth defects, medication exposures, abnormal serum screening tests, or advanced maternal age.
Serum Screening tests are blood tests that can be easily and safely performed on a large group of women to identify those women whose fetuses may need further testing.
An abnormal screening test does not mean your baby has a birth defect or other problem, but does suggest the need for closer evaluation. On average, only 1-5% of women with abnormal serum screening have a pregnancy with an increased risk for complications. Further testing may include targeted ultrasound, genetic counseling, amniocentesis, fetal monitoring later in pregnancy, or additional blood screening.
Genetic Counseling is an opportunity to review you and your partner's family history. This will help determine if there is an increased risk of genetic diseases that may run in your family. This is also an opportunity to best determine the risks involved in your pregnancy and answer any questions you may have concerning the prenatal diagnostic testing that is available. Our philosophy in the Antenatal Testing Unit is that of "non-directive counseling" where we will provide you with the medical and genetic information available to help you come to a personal decision that is appropriate for you.
Ultrasound can detect many, but not all birth defects. Some birth defects may be difficult to see in the fetus. Some may not appear until the fetus has grown to a certain size. In some birth defects, like Down syndrome, only half of the fetuses will have features that look different from normal babies. Most large studies suggest that ultrasound can pick up over half of the birth defects found at birth and that specialized ultrasound can pick up twice as many birth defects as ultrasounds performed in a doctor's office.
A Serum screening test (triple or quad screening test) is a blood test that measures the levels of certain proteins and hormones produced by the fetus. These include alpha-fetoprotein (AFP), human chorionic gonadatrophin (HCG), and estriol. The newest variation, known as a Quad screen includes these three proteins and another protein, inhibin, for a total of 4 serum analytes.
The screening tests may be abnormal if the level of AFP is too high. This raises the possibility that the fetus may have an abnormality of its spine, spina bifida. On the average, only 3-5 babies out of 100 whose mothers have a high AFP actually have a birth defect.
The screening test may also suggest an increased risk for Down syndrome. This typically results when your AFP level is low and your HCG level is high. Again, only a small percentage of women who have this result actually have a baby with Down syndrome. The test results predict a chance based upon your age and test results, but on the average only 1 woman in 150 who have an abnormal result actually have a baby with Down syndrome. In this situation, an amniocentesis can tell your baby's chromosome results.
Down syndrome is the most common chromosomal birth defect. It occurs in approximately 1/700 pregnancies. It results when a fetus possesses three, rather than the usual two, copies of the 21st chromosome. This extra genetic material affects a person's physical and cognitive development. Most people with Down syndrome have some level of mental retardation, however, the level usually falls into the mild to moderate range. Children with Down syndrome learn to sit, walk, talk, play, toilet train and do most other activities - only somewhat later than their peers without Down syndrome. Some couples believe it is very important to know whether their fetus may have Down syndrome as it may affect their decisions to continue the pregnancy or prepare for the birth.
We in the Antenatal Testing Unit acknowledge and respect the different personal beliefs of our patients and help to provide them with the medical information necessary to make the right decisions for them.
