CONTINUOUS MECONIUM MONITORING DURING LABOR USING AN INTRAUTERINE PROBE

The fetus discharges meconium (its bowel contents) into the amniotic f luid during labour in approximately 10% of pregnancies. In about 10% o f cases where meconium is passed, the fetus gasps, inhaling the sticky meconium into the upper respiratory tract. After birth, the meconium blocks the air passages in the lungs, impairing gas exchange (meconium aspiration syndrome, MAS). Up to 20% of infants suffering from MAS di e and recently published studies have shown a long-term effect Of MAS in causing cough and wheeze. At present, meconium is only noticed at b irth or occasionally when amniotic fluid leaks past the presenting par t of the fetus. We have developed a system to monitor meconium continu ously during labour, using a flexible intrauterine probe. The system p rovides a measurement of the meconium concentration of amniotic fluid during labour every 2 min, with a 60% prediction interval of +/-10 g l -1, and a 99% prediction interval of +/-30 g l-1 (clinically 'thick me conium' contains around 100 g l-1). The noise of the measurement is of the order of +/-10 g l-1, and the response to changes in the meconium concentration is from 40 to 120 s, depending on its configuration. Th e system also provides other obstetric variables such as fetal heart r ate and uterine activity measurement, obtained from a fetal monitor. P reliminary clinical results indicate that this system can measure meco nium not apparent to the attending staff; the system can detect change s in the meconium concentration of amniotic fluid; the measurements ar e confirmed by visual observation at delivery; and changes of meconium concentration seem to correlate with known stressful stimuli. The sys tem therefore provides a new tool from which new variables are obtaine d, which can greatly enhance clinical research into the pathophysiolog y of meconium passage and aspiration.