Contribution of cerebral doppler in the evaluation of fetal well being
De Rochambeau, B.
Revue Francaise de Gynecologie et d'Obstetrique 86(11): 677-681
1991
ISSN/ISBN: 0035-290X PMID: 1780622 Document Number: 374390
Foetal well being is assumed in normally proceeding pregnancies. In pregnancies with a risk of foetal distress, the obstetrician now has the possibility of carrying out foetal cerebral hemodynamic exploration in order to reach a short-term prognosis. The brain of the foetus is a hemodynamically privileged site in cases of hypoxic foetal distress; this brain-sparing effect gives rise to Doppler velocimetric signs which are seen in animal and human foetuses. Cerebral resistance, measured in Doppler velocimetry from the resistance index R = (S.D)/S falls at the beginning of the last third of pregnancy, but remains higher than placental resistance. This is due to the considerable development of foetal brain vascularization from this time forward. Inversion of the ratio between the cerebral index (CRI) and the umbilical index (PRI) and a marked reduction of the cerebral index below the normal range demonstrates the brainsparing effect during hypoxic distress. In cases of delayed intra-uterine growth, this signs is linked to a high probability of forthcoming acute foetal distress (AFD). In hypertension of pregnancy, the fall in CRI is closely correlated with a high Caesarian rate due to AFD and a higher morbidity level and neo-natal sequelae. The prognosis for these foetuses therefore depends on their gestational age: it is good after 34 weeks of amenorrhea, but remains doubtful between 28 and 34 weeks of amenorrhea. In these cases, the administration of oxygen to the mother for 20 minutes (FLO2 = 70%, 8 l/min) constitutes a prognostic test. The foetuses whose CRI is corrected have a better prognosis than the others, if the pregnancy continues up to the change in foetal cardiac rhythm.