General information
Other names
FIGURE Fetal Blood Test
Preparation
| Where It's Done | Who Does It | How Long It Takes | Discomfort/Pain |
| Hospital or doctor's office. | Doctor and sonographer. | 5 minutes to 1 hour. | Similar to having blood drawn. |
| Results Ready When | Special Equipment | Risks/Complications | Average Cost |
| A few minutes to a few days, depending on the extent of testing. | Spinal needle and ultrasound equipment. | Risk of miscarriage about comparable to amniocentesis (1%-2%), infection, and temporary slowing of fetal heartbeat. | $$$ |
Cordocentesis, fetal blood sampling, umbilical cord blood testing, and percutaneous umbilical blood sampling (PUBS).
Purpose- To rapidly verify the presence of Down syndrome or another fetal chromosomal abnormality.
- To evaluate the presence of chromosomal abnormalities when CVS results are ambiguous.
- To detect the presence of infectious disease such as toxoplasmosis, rubella, or cytomegalovirus in the fetus, so that it can be treated.
- To perform a blood count and check for anemia or low platelet levels in the fetus.
A sample of the baby's blood is withdrawn from the umbilical cord and analyzed (see figure).
Guided by ultrasound, the doctor inserts a thin hollow needle through the abdominal wall and into the uterus to withdraw a sample of blood from the umbilical cord.
- If you are in the third trimester you may have to fast overnight in case an emergency cesarean delivery is required.
- Your abdomen is cleansed with an antiseptic solution.
- Guided by an ultrasound image, the doctor introduces a long, thin needle through the abdomen and uterus into the umbilical cord.
- About a teaspoon of blood is drawn and checked to be sure it is fetal blood; a second sample may be taken.
- The baby's heartbeat is monitored during the procedure.
- Your breathing and pulse and the baby's heartbeat are monitored for about an hour, after which you are free to leave.
- Avoid strenuous activities for 24 hours.
- Contact your doctor immediately if you experience abdominal cramps, vaginal bleeding, leakage of amniotic fluid into your vagina, unusual behavior of the fetus, or anything else that feels abnormal.
The presence of maternal blood or amniotic fluid in the sample distorts results.
Interpretation- The blood is analyzed for the same conditions as in CVS.
- The blood may be examined for the presence of antibodies.
- It allows rapid evaluation of fetal chromosomes when quick decisions must be made about ending the pregnancy or delivering by cesarean section.
- It can help avoid abortion when the mother has an infection potentially threatening to the fetus but the fetus is not infected.
It has limited availability.
The next stepIf an abnormality is detected, you will be referred to a genetic counselor, who can explain the implications of the test results.
