Fetal blood sampling (FBS) is the collecting of fetal blood
directly from the umbilical cord or fetus. The fetal blood is tested for signs
of
anemia and other blood problems. FBS is also known as
cordocentesis or percutaneous umbilical cord blood sampling.
FBS is usually used when a
Doppler ultrasound and/or a series of
amniocentesis tests have first shown moderate to
severe anemia.
If you are
Rh sensitized and you are carrying an Rh-positive
fetus, your
immune system can attack the fetus's red blood cells.
FBS is used to look at a fetus's red blood cell count and oxygen level, as well
as signs that your immune system is destroying fetal red blood cells.
FBS is performed in a hospital's outpatient surgery department. You
will probably be given a
sedative to reduce your and the fetus's movement
during the FBS procedure.
The fetus may be given an injection of
medication that temporarily stops movement.
A small area of your
abdomen is numbed with an injection of
local anesthetic.
Ultrasound is used to
guide a needle through your abdomen into an umbilical vein in the
umbilical cord.
A small amount of blood is
withdrawn into the needle and collected.
You may be given additional medication during FBS, such as
antibiotics to prevent infection or medication to prevent preterm labor
(tocolytic drugs).
In the second trimester, fetal blood sampling (FBS) gives the best
data about a fetus's anemia, blood oxygen levels, and red blood cells.1
If Doppler ultrasound and/or amniocentesis tests show moderate to
severe anemia, FBS is then used. FBS is usually reserved for use after these
tests because of its greater risks—up to 2% of pregnancies miscarry after FBS,
and up to 50% lead to worsened Rh sensitization problems. (This happens after
fetal blood mixes with mother's blood during the blood sampling.)2
FBS is usually used when a Doppler ultrasound and/or a series of
amniocentesis tests have first shown moderate to severe anemia. Fetal blood
tests show the oxygen level, red blood cell condition, and red blood cell
count. This helps your doctor plan the best treatment for you during your
pregnancy.
If the effects of Rh sensitization are severe and the fetus has
severe anemia, a fetal
blood transfusion may be done immediately. Future
transfusions may be scheduled to keep the fetus healthy until it can be
delivered safely.
Porter TF, et al. (2003). Immunologic disorders in
pregnancy. In JR Scott et al., eds., Danforth's Obstetrics and
Gynecology, 9th ed., pp. 313–338. Philadelphia: Lippincott Williams and
Wilkins.
Moise KJ (2004). Hemolytic disease of the fetus and
newborn. In RK Creasy, R Resnik, eds., Maternal-Fetal Medicine:
Principles and Practice, 5th ed., pp. 537–561. Philadelphia:
Saunders.
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information. For more information, click here.
