Prenatal TestingWednesday, April 18, 2012 - 13:42
Some tests, called indicated tests, are usually reserved for women who are considered at increased risk due to something her medical or genetic history or an abnormal result in a screening test. However, some indicated tests, such as ultrasound, are being used more often during pregnancy, regardless of whether the mother or fetus is at risk of health problems.
Prenatal tests include:
- Contraction stress testing
- Non-stress testing
- Fetal motion count
- Other screening tests
Ultrasound, or sonogram, uses high frequency sound waves to form an image of the uterus,
- Growth of the fetus
- Abnormalities of the fetal structures such as heart, brain, limbs, kidneys, and stomach
- Birth defects
- Amount of
- Location and development of the placenta
- Gestational age or duration of the pregnancy
The test can be performed almost any time during pregnancy. In the earliest months, it can be performed with a probe placed in the vagina. However, most are performed with a wand placed on the abdomen over the uterus.
Between 15 and 18 weeks, the doctor may perform a test to determine the level of
High AFP levels will occur with twin pregnancies. Also, measuring AFP can help determine the presence of a type of birth defect called a
This test uses a fetal monitor to continuously record the baby's heart rate and
In this procedure, the fetal monitor is attached to the mother's abdomen and records the fetal heart rate. The doctor listens for increases, or accelerations, in the fetal heart rate. If the baby is believed to be asleep, a buzzer is sounded to awaken the fetus. Like contraction stress testing, this test is also performed when the fetus is believed to be at increased risk for stillbirth, but it does not require uterine contractions. A flat fetal heart rate can indicate an increased risk of stillbirth.
There are a variety of ways in which this test is performed but all rely upon a sudden change in the number of fetal movements in a specified period of time. In most cases, the mother keeps track of the number of times she feels the baby move. Further tests will be performed if the mother notes a sudden decrease or absence of movements. Although some physicians use this procedure because it is easy to use and inexpensive, the appropriate role of fetal motion counting in prenatal care is controversial.
The amniotic fluid that surrounds the growing fetus can yield important information. Amniocentesis allows a small sample of this fluid to be collected for analysis. Using sonogram as a guide, doctors insert a long, thin needle through the abdominal wall and the wall of the uterus into the fluid cavity surrounding the fetus.
Nice To Know:
Amniocentesis is usually offered to women who are at an increased risk for having a baby with a birth defect. These women include those who will be age 35 or older on their due date and those who have a history of birth defects in their immediate family.
Amniocentesis may be done for many reasons:
- To identify genetic defects
- To test for fetal lung maturity
- To detect isoimmunization to Rh factor
Genetic amniocentesis. One of the most common reasons for amniocentesis is to identify genetic defects. Genes carry the master plan of a person's physical makeup. Because the amniotic fluid and the developing fetus are formed from the same cells, they share the same genetic makeup. Amniotic fluid can therefore be studied to see whether the fetus's
Amniocentesis for fetal lung maturity. This test is performed if there is concern that the infant may be at risk for lung development problems. In order to remain open, the lungs require a substance known as
Amniocentesis for isoimmunization. Isoimmunization occurs when Rh or other
For more detailed information about Anemia, go to Anemia.
A number of other screening tests provide further assurance that a baby is progressing normally.These tests include:
- Human chorionic gonadotropin (HCG). This substance can be measured in blood or urine samples taken from the mother. The most common reason to measure HCG is to diagnose pregnancy. However, physicians also use HCG testing to detect Down syndrome in a fetus.
Estriol. Earlier in pregnancy, this measurement can be used in conjunction with maternal age, AFP, and HCG to help in the prediction of Down syndrome.