FETAL OXYGEN-SATURATION MEASURED BY PULSE OXIMETRY DURING LABOR WITH CLEAR OR MECONIUM-STAINED AMNIOTIC-FLUID

Objective: To compare fetal oxygen saturation, scalp pH and arterial c ord blood gases in cases of clear or meconium-stained amniotic fluid w ith and without meconium aspiration (MAS). Study design: Thirty-eight women in labour at term with abnormal fetal heart rate were included. Fetal oxygen saturation was continuously monitored using a Nellcor N-4 00 fetal pulse oximeter and FS-14 sensor. Fetal scalp blood samples we re taken systematically at full dilatation or immediately before cesar ean section. Arterial cord blood gases were analysed at birth. Fetal o xygen saturation, scalp pH and neonatal blood gases were compared betw een fetuses with clear amniotic fluid, meconium-stained amniotic fluid without MAS and meconium stained amniotic fluid with MAS. Results: Mo derate or thick meconium was observed in 13 cases during labour. Three newborns had a meconium aspiration defined as meconium below the voca l cords. No differences were observed in scalp pH, scalp base excess, umbilical arterial blood pH or base excess between groups. On the othe r hand, fetal oxygen saturation (fSpo(2)) obtained before birth was si gnificantly lower in cases of MAS when compared to the other groups. T his difference appears to be large compared to that which might be att ributed to meconium and its direct effect on fetal pulse oximetry read ings. Fetal oxygen saturation dropped dramatically in cases with mecon ium aspiration between the first stage of labour (44.7 +/- 8.0%) and t he last measurement before birth (27.0 +/- 8.5%). Conclusion: Meconium aspiration is more likely to be associated with fetal hypoxemia than with fetal acidosis. (C) 1997 Elsevier Science Ireland Ltd.