Evaluation of the Baby's Development During Pregnancy
Pregnancy is a very exciting time for parents but can also be a time of anxiety and concern for the unknown. Prenatal testing includes all of the different evaluations available that can provide information about the health of the developing baby. Some tests may be offered only in pregnancies known to be at higher risk for a genetic condition or birth defect. Other tests are offered in all pregnancies. The following summary of screening and diagnostic testing options will provide initial information for parents. Please discuss your particular needs with your prenatal care providers. The decision to have testing during pregnancy is a very personal one. Keep in mind that the vast majority of babies are healthy at birth. The testing during pregnancy therefore usually provides additional reassurance to parents. In cases where a birth defect or genetic condition is identified, parents will receive detailed information about what they may expect and options for managing that pregnancy. High risk pregnancies carried into the third trimester are followed very closely to maximize the health and well-being of the baby.
Screening Tests
Screening tests, available to all women, are used to predict the chance of some birth defects or genetic conditions of the baby. The test results include information on the mother's age, medical and family history, and on information from the developing baby itself. These are not invasive tests, and do not increase the risk for miscarriage. If the screening tests suggest an increased risk for a specific birth defect or genetic condition, further evaluation will be offered.
Ultrasound: These are evaluations of the physical development of the baby. First Trimester ultrasound can be used to evaluate the very early development. General assessment of the head, body, limbs, umbilical cord, and placenta can be done. A measurement of the fluid under the skin of the neck (nuchal translucency) may be taken as well. These early pictures occasionally suggest an increased risk for problems with the developing baby and allow parents the option of choosing further testing.
Second trimester ultrasound can be used to evaluate the ongoing development of the baby. At 20 weeks of pregnancy the brain, heart, spine, kidneys, bladder, stomach, umbilical cord, and limbs can be more closely assessed. If concerns regarding the appearance of the baby are identified, the parents may be offered diagnostic testing and/or referral for additional expertise at a perinatal clinic such as University of Washington or Swedish Medical Center.
Third trimester ultrasound is used to follow the growth of the baby, evaluate for evolving problems, or to evaluate the well-being of the baby. These are done in high-risk pregnancies or in pregnancies where the standard, simple evaluation in the clinic exam room is not able to provide enough reassurance about how the baby is doing.
Maternal Serum Screening: These are evaluations of proteins produced by the pregnancy and released into the mother's blood stream. A blood sample is drawn from the mother and the amount of specific proteins is measured. A first trimester blood test between 11 and 13 weeks measuring two proteins (Integrated Screening) as well as a second trimester test between 15 and 22 weeks measuring four proteins (the Quad Screen) is available. Based on the amount of the proteins found, a specific prediction for the chance of a genetic condition or birth defect is made. If the chance of a genetic condition or birth defect is predicted to be higher than originally thought, further testing such as ultrasound, amniocentesis, or chorionic villus sampling may be offered.
Diagnostic Tests
Diagnostic tests include chorionic villus sampling and amniocentesis. These tests are able to directly evaluate the baby and are therefore considered to be as accurate as humanly possible. These tests are primarily for identifying a genetic or chromosome condition such as Down Syndrome. There are many conditions which are able to be diagnosed this way. Chorionic villus sampling tests a tiny amount of tissue from the placenta and is done between 11 and 13 weeks. This test is done by either inserting a skinny needle through the mother's abdomen, or by inserting a tiny catheter through the cervix. The placenta and the baby come from the same fertilized egg and in general have the same genetics. An amniocentesis tests cells from the baby which are floating in the amniotic fluid. The genetic material in these cells is examined after the cells are grown in the laboratory. This test can be performed after 15 weeks or so and is done with a skinny needle inserted through the abdomen.
Diagnostic tests are offered in addition to screening tests to all women age 35 and older at delivery, to some women who have had a previous child with a birth defect or genetic condition, and to women who have had a screening test which has predicted an increased risk for a genetic condition or birth defect. Again, as with the screening, patients offered diagnostic tests may be referred to Seattle if additional expertise is needed.
MATERNAL AGE and CHROMOSOMAL ABNORMALITIES
Maternal Age |
Risk of Down's Syndrome |
Total Risk for Chromosomal Abnormalities |
Maternal Age |
Risk of Down's Syndrome |
Total Risk for Chromosomal Abnormalities |
|
20...... |
1/1,667 |
1/526 |
35....... |
1/385 |
1/204 |
|
21...... |
1/1,667 |
1/526 |
36....... |
1/294 |
1/164 |
|
22...... |
1/1,429 |
1/500 |
37....... |
1/227 |
1/130 |
|
23...... |
1/1,429 |
1/500 |
38....... |
1/175 |
1/103 |
|
24...... |
1/1,250 |
1/476 |
39....... |
1/137 |
1/82 |
|
25...... |
1/1,250 |
1/476 |
40....... |
1/106 |
1/65 |
|
26...... |
1/1,176 |
1/476 |
41....... |
1/82 |
1/51 |
|
27...... |
1/1,111 |
1/455 |
42....... |
1/64 |
1/40 |
|
28...... |
1/1,053 |
1/435 |
43....... |
1/50 |
1/32 |
|
29...... |
1/1,000 |
1/417 |
44....... |
1/38 |
1/25 |
|
30...... |
1/952 |
1/384 |
45....... |
1/30 |
1/20 |
|
31...... |
1/909 |
1/384 |
46....... |
1/23 |
1/15 |
|
32...... |
1/796 |
1/322 |
47....... |
1/18 |
1/12 |
|
33...... |
1/625 |
1/317 |
48....... |
1/14 |
1/10 |
|
34...... |
1/500 |
1/260 |
49....... |
1/11 |
1/7 |
|