Although meconium can be present in the amniotic fluid in normal deliveries, aspiration of meconium into the lungs is usually a manifestation of fetal asphyxia. Consequently, newborns with meconium aspiration syndrome frequently have evidence of hypoxic damage in multiple systems. Because of the severity of the pulmonary involvement, these other manifestations of hypoxia tend to be overlooked unless they become life threatening. During labor and delivery many situations may arise that can interfere with the exchange of gases between mother and fetus producing different degrees of fetal asphyxia. For example, decreased uterine blood flow may result from maternal arterial hypotension or hyperdynamic uterine activity. Premature separation of the placenta acutely reduces the surface available for gas exchange, and blood flow through the umbilical cord can be reduced by true knots or by compression of a prolapsed cord. Any of these situations can produce a fall in PaO2 and an increase in PaCO2 and hydrogen ion concentration in the fetal blood within a few minutes. The intensity and duration of the asphyxia determine whether or not the fetus will survive, and if it does, whether transient or permanent neurological damage will be produced. Although modern obstetrics and the use of fetal monitoring can reduce the risk of severe fetal asphyxia, there are many cases in which problems interfering with fetal oxygenation cannot be anticipated or corrected rapidly. Thus the neonatologist continues to be faced frequently with infants who have suffered significant degrees of asphyxia.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health
- Obstetrics and Gynecology