Human fetal and maternal noradrenaline responses to invasive procedures

Fetal and maternal plasma noradrenaline responses to invasive procedures we re determined in pregnancies of 18 to 37 wk gestation. Fetal umbilical veno us blood sampling was performed either from the placental cord insertion, w hich is not innervated, or the intrahepatic vein, which is innervated, and thus may be more stressful for the fetus. Samples from diagnostic procedure s, as well as from transfusion procedures, were compared between the two si tes. Fetal plasma levels were significantly elevated in blood samples obtai ned from the intrahepatic vein compared with those from the placental cord insertion during diagnostic procedures [p < 0.05, geometric means and 95% c onfidence intervals (CI) were 0.67 nmol/L (0.43-1.04) and 0.36 nmol/L (0.25 -0.54), respectively]. Plasma levels in samples taken before transfusion fr om the intrahepatic vein were also significantly higher than those from the placental cord insertion. After transfusion, there was a significant rise in fetal plasma noradrenaline levels at both sites; however, after transfus ion through the intrahepatic vein, the rise was substantially greater than after transfusion through the placental cord insertion (p < 0.05, change, m ean Delta(NA), and 95% CI were 0.67 (0.37-1.22), and 0.20 (0.12-0.33), resp ectively). The Delta(NA) was significantly associated with the duration of the stimulus (the time the needle remained in situ) (p = 0.05, adjusted R-2 = 0.48) and with gestational age. Maternal levels rose substantially and e qually after transfusions at either site (mean Delta(NA) and 95% CI, 6.46 n mol/L, 1.74 to 11.18 and 9.49 nmol/L, 6.24 to 12.75 for the intrahepatic ve in and placental cord insertion groups, respectively). There was no signifi cant correlation between baseline fetal and maternal levels (r = 0.08, n = 41) or between Delta(NA) pre- and posttransfusion maternal and fetal values in either group, These results indicate that the fetus is capable of mount ing an independent noradrenaline stress response to a needle transgressing its trunk from 18 wk gestation. The effect was observable in samples taken at a mean of 5.6 min after needling. The lack of correlation between matern al and fetal levels suggests that virtually no noradrenaline crosses the pl acenta directly, and that the observed fetal responses are not due to direc t transport from the mother.