Acute increase in femoral artery resistance in response to direct physical stimuli in the human fetus.

Abstract

To determine whether fetal response to needling resembles the fetal 'brain sparing' response seen with hypoxaemia. Prospective observational study. Centre for Fetal Care, Queen Charlotte's and Chelsea Hospital, London. Eighty-five pregnant women undergoing invasive procedures associated with fetal prenatal diagnosis and/or management. The femoral artery and the middle cerebral artery pulsatility index were measured by Doppler ultrasonography before and after 89 invasive procedures (fetal blood sampling, transfusion, bladder or cyst aspiration, shunt insertion and amniocentesis, between 17 and 36 weeks). Cases in which the fetal body was transgressed were compared with 'control' fetuses undergoing invasive procedures which did not directly involve needling the fetus (amniocentesis and placental cord insertion procedures). Femoral artery and middle cerebral artery pulsatility index. The femoral artery pulsatility index rose after transgression [median change (Delta) 0.73; 95% confidence interval (CI) 0.51 to 0.98]. In contrast, there was no significant change in femoral artery pulsatility index after non-transgression procedures (mean Delta 0.28; 95% CI -0.20 to 0.76). Analysis confirmed the fall in middle cerebral artery pulsatility index after transgression procedures (median Delta -0.19; 95% CI -0.07 to -0.35), but there was also a significant fall in middle cerebral artery pulsatility index after non-transgression procedures (mean Delta -0.47; 95% CI -0.23 to -0.71). The human fetus mounts a peripheral haemodynamic response to invasive procedures involving transgression of the fetal body, which is consistent with the brain sparing effect. However, the change in middle cerebral artery pulsatility index in both transgression and control procedures suggests that the changes and mechanisms may be more complex than previously thought.