Clinical significance of fetal heart rate patterns during labor. I. Baseline patterns

From a population of 2,774 high-risk patients monitored during labor, 1,304 single pregnancies in cephalic presentation and with direct monitoring for at least 1 hour before completion or cesarean-section were studied. The maternal and fetal clinical data and the tracings were hand reviewed, coded, and programmed for computer analysis. In the record were studied baseline, its changes (tachycardia, fixed, saltatory), the accelerations, and the decelerations (early, variable, late). Fifty-four per cent had some type of FHR deceleration. Accelerations were recorded in over 12 per cent of all cases and were associated with cord problems in 41 per cent. Subgrouping the patients by age of gestation (less than or equal to 36 weeks, 37 to 41 weeks, and greater than or equal to 42 weeks) revealed a 10 per cent prolonged gestation rate and only 6.8 per cent premature; these had a lower 5 minute Apgar score. Fetal weight and age were positively correlated with Apgar score. Baseline changes were much frequent among pre- and postmature infants, particularly tachycardia in the latter (40 per cent). The premature infants had a 25 per cent incidence of fetal distress and the postmature infants had 20 per cent. Neonatal morbidity and mortality rates were very high among premature infants and a mortality rate of 2.3 per cent was found among postmature infants. Saltatory pattern and particularly fixed baseline seem characteristic of prolonged gestation and placental insufficiency. With tachycardia, they constitute subtle symptoms of fetal distress.