Fetomaternal transfusion after amniocentesis and cordocentesis.

OBJECTIVE: To compare the extent of fetomaternal transfusion after amniocentesis and cordocentesis. SETTING: Three-hundred and forty-five amniocentesis and 268 cordocentesis were performed for genetic indications. The extent of fetomaternal transfusion was calculated on the basis of the maternal serum alpha-fetoprotein level changes. RESULTS: The mean fetomaternal transfusion was 6.3 and 62 muL in the amniocentesis and cordocentesis groups, respectively. Transplacental needle passage and longer procedural time were risk factors for fetomaternal transfusion. The frequency of transplacental passage was higher and the procedural time was longer in the cordocentesis group. The fetal loss rate was 1.17% after amniocentesis and 1.2% after cordocentesis, respectively. CONCLUSIONS: Cordocentesis causes more injury to the extrafetal compartment, which results in a higher level of fetomaternal transfusion. However, though a nearly ten times higher fetomaternal transfusion was observed after cordocentesis, there was no essential difference in pregnancy outcome between the two groups