The indirectly obtained fetal heart rate: comparison of first- and second-generation electronic fetal monitors.

Fetal heart rate variability has become an essential component in evaluation of the fetus during continuous electronic fetal monitoring. Because of technical deficiencies of monitoring equipment, fetal heart rate variability may not always be available, such as during indirect monitoring of the fetus. In lieu of integration, a mathematical procedure called autocorrelation has, with the use of microprocessors, been incorporated into the fetal monitor, creating the "second generation" of electronic fetal monitoring. This study examined the accuracy of the first- and second-generation monitors by comparing simultaneously obtained indirect and direct real-time fetal heart rate data. The second-generation monitor produced an indirectly obtained fetal heart rate that was more accurate when compared with the directly obtained data than that with the first-generation fetal monitor. In addition, the variation in data from the first-generation monitor was substantially higher than that with the second-generation monitor. It is concluded that the fetal heart rate tracing from the second-generation monitor is more accurate when compared with the fetal electrocardiogram and may facilitate a truer interpretation of fetal heart rate variability than that obtained with the first-generation monitor.

Correlation of the one-minute Apgar score and umbilical cord acid-base status.

The one-minute Apgar score has proven useful by ensuring rapid assessment of the neonate, but is often poorly correlated with other indicators of intrauterine well-being. Since fetal asphyxia is directly associated with neonatal acidosis, a low Apgar score in the face of normal pH and base deficit does not indicate an asphyxiated infant. In a study to ascertain the feasibility of combining umbilical artery pH with the one-minute Apgar score for neonatal assessment, umbilical artery pH and Apgar scores were obtained on 212 singleton pregnancies. When the Apgar score was less than 7, more than half (60%) of the neonates had a normal umbilical artery pH. Fifty-one percent of this group had had intubation and nasopharyngeal suctioning, procedures known to be associated with lowered Apgar scores. When reviewing the umbilical artery gas values and base deficit in those neonates with a pH less than 7.20, we found that of the eight patients with an Apgar score of 7 or greater, seven (87.5%) were classified as having metabolic acidosis, with only one having respiratory acidosis. In the neonates with Apgar scores of less than 7, approximately two thirds had blood gas values compatible with metabolic acidosis, while the others displayed respiratory acidosis. We recommend, therefore, that neonates with a one-minute Apgar score less than 7 have umbilical artery pH determinations to confirm the presence or absence of acidosis. We also recommend that when the pH is less than 7.20, a complete set of gas values be evaluated with that specimen. This information offers more precise confirmation of the diagnosis of fetal distress and neonatal asphyxia, both for treatment and more reliable follow-up data, as well as for medicolegal purposes.

Antepartum fetal monitoring in insulin-dependent diabetic pregnancies.

In order to minimize unexplained stillbirths in insulin-dependent diabetic pregnancies, fetal well-being was assessed by antepartum monitoring while development of pulmonary maturity was awaited. Antepartum monitoring consisted of outpatient nonstress tests beginning at 32 weeks' gestation. Fetuses with nonreactive nonstress tests were further evaluated by contraction stress tests and were delivered if tests were positive. With use of this system there were no unexplained stillbirths during management of 119 insulin-dependent diabetic pregnancies. Of 14 infants delivered because of positive contraction stress tests, six were found to have major disorders; the other eight had no major residual neonatal morbidity. Thus this system of antepartum fetal surveillance: eliminated unexplained stillbirths, identified a subgroup of insulin-dependent diabetic pregnancies with a high rate of major fetal abnormalities, and allowed for identification and subsequent timely delivery of the other distressed fetuses that were at a high risk of neonatal morbidity and/or mortality, such that potential long-term adverse outcomes were avoided.

Correlation of the one-minute Apgar score and the pH value of umbilical arterial blood.

The one-minute Apgar score, proven useful for rapid assessment of the neonate, is often poorly correlated with other indicators of intrauterine well-being. Fetal asphyxia is directly associated with neonatal acidosis. A low Apgar score in the face of normal pH and base deficit does not, therefore, indicate an asphyxiated infant. We performed a study at Vanderbilt University Hospital to ascertain the feasibility of combining the pH value of umbilical arterial blood with the one-minute Apgar score for neonatal assessment. The pH values and Apgar scores were obtained on 172 singleton neonates. When the Apgar score was less than 7, over one half (56%) of the neonates had a normal pH value. Of this group 46% had undergone intubation and nasopharyngeal suctioning, procedures known to be associated with lowered Apgar scores. We recommend, therefore, that neonates with a one-minute Apgar score of less than 7 be further evaluated with umbilical arterial blood gas studies to ascertain the presence of acidosis and to differentiate between metabolic and respiratory acidosis. More precise confirmation of the diagnosis of fetal distress and neonatal asphyxia, for both treatment and medicolegal purposes, is possible with this information.