Sonography-guided fetal blood sampling for pH and blood gases in premature fetuses with abnormal fetal heart rate traces.

In nine pregnancies, remote from term, with an abnormal Non-Stress Test (NST) and Bio-Physical Profile (BPP) of 3 or above, cordocentesis for fetal blood gas analysis was performed. In seven cases an immediate post-partum blood sample was taken from the fetal cord for a similar analysis. The two tests gave very similar results. The results showed fetal acidemia (pH 7.09-7.19 and B.E. -10-15) in 4 cases, followed by immediate delivery. In the remaining 5 cases, normal blood gases were evident (pH 7.28-7.35); despite the abnormal NST, pregnancy was allowed to continue for 2 to 7 weeks, under close supervision. At birth, 2 out of 9 newborns were deemed by the neonatologist suffering from asphyxia. Both belonged to the acidemic group of women who were managed by immediate cesarean section. The other 5 fetuses, which were managed expectantly, had normal post-partum blood gases or Apgar score; none had asphyxia. Fetal blood gas analysis, on samples obtained by cordocentesis, provides useful information that can assist in the management of premature fetuses suspected of being distressed, according to their heart traces. Normal fetal blood gases can identify those fetuses falsely identified by the NST as in distress and thereby spare them unnecessary premature birth with its known complications.