Cordocentesis is a procedure that takes a blood sample from one of the blood vessels in the baby's umbilical cord, to directly test the baby's blood. Cordocentesis can only be done later in the pregnancy, from about 18 - 24 weeks, when the umbilical cord has adequately developed.
Cordocentesis involves the doctor using ultrasound images to guide the insertion of a long, thin needle through the woman's belly and uterus and into the umbilical cord, at the end closest to the
placenta. A small blood sample is then taken and the needle is removed. The baby's heartbeat is
continuously monitored during the procedure, which can take up to 1 hour.
No anaesthetic is required for cordocentesis, but the procedure may be slightly uncomfortable for some women with cramping or contractions during the procedure and for a few hours or a day or two afterwards. Some women experience a small amount of vaginal bleeding (although this is not common) and few women will experience their waters leaking (or some of the amniotic fluid coming away). It is recommended that you take complete rest for about 24 hours after the procedure.
A cordocentesis may be used if an amniocentesis or CVS have been unsuccessful, or the tests results from these tests were inconclusive. Cordocentesis can rapidly identify genetic disorders (such as Down syndrome) within 48 hours. The test may also be used to detect blood disorders in the baby such as haemophilia or for other medical reasons such as checking the baby for a suspected viral infection, such as
rubella,
toxoplasmosis , or
cytomegalovirus , or to see if the baby is anaemic with
isoimmunisation.
Cordocentesis has a miscarriage (or premature birth) rate of about 1 to 2% (1:100 to 1:50) as well as a small risk of infection. Sometimes the baby's heartbeat temporarily slows during the procedure. If the pregnancy is quite advanced (more than 26