Correlation of neonatal acid-base status with Apgar scores and fetal heart rate tracings

In this study the immediate neonatal acid-base status, obtained via a double-clamped segment of umbilical cord, in 75 term, singleton vaginal deliveries was compared to electronic fetal heart rate recordings and Apgar scores. Of 75 neonates, 59 had 1-minute Apgar scores greater than or equal to 7 and 52 had an initial pH greater than 7.20. Six of the 16 neonates with a 1-minute Apgar score less than 7 demonstrated a low pH (less than 7.20). At 5 minutes only eight of 75 neonates had Apgar scores less than 7 with six of the eight having pH values less than 7.20. Of those neonates with Apgar scores greater than or equal to 7 and pH less than 7.20 (seven neonates at 1 minute, two at 5 minutes), none had metabolic acidosis. Eighteen fetal heart rate tracings were considered abnormal; acidosis was confirmed in eight (44%) by pH criteria, yet only three of the eight neonates had low Apgar scores. Our investigations suggest that the combination of fetal heart rate monitoring, cord blood pH, and Apgar assessment is better than any one parameter alone as an evaluation of fetal status just after delivery.     

Neonatal acidosis and method of delivery

Seven hundred and four women who had a forceps termination (177 elective, 293 indicated low, and 234 indicated midforceps) of labor over 24 months were compared with 303 spontaneous and 111 cesarean deliveries over the same time period. There was no significant difference between indicated low or midforceps either for fetal distress or arrest of descent with regard to fetal acidosis (pH less than 7.20), one- or five-minute Apgar scores less than 7, fetal trauma, or neurologic deficit at discharge. Fourteen percent of indicated forceps for arrest of descent had neonatal acidosis, versus 8% of cesarean sections for cephalopelvic disproportion (P = NS), and 23% of indicated forceps for fetal distress had acidosis, versus 33% of cesarean sections (P = not significant). There was no significant difference either in the incidence of acidosis or in low Apgar scores in neonates delivered by elective low forceps compared with those born by spontaneous vaginal delivery. The only significant differences in midforceps versus low forceps were between maternal pre- and postdelivery hematocrits (P less than .0001) and vaginal lacerations (P less than .0001). The authors' data support the continued usage of indicated low and selected midforceps operations.     

Status of infants at birth and risk for adverse neonatal events and long-term sequelae: a study in low birth weight infants

We evaluated the relationship of infant status at birth to neonatal morbidity and long-term development in 246 low birth weight infants (600 to 1750 gm). Nineteen percent of infants had 1-minute Apgar scores of less than or equal to 3, and 8% had an umbilical artery pH of less than or equal to 7.2. Acidosis was associated with an increased risk of grade 3 to 4 intracranial hemorrhage (odds ratio = 3.3). Low 1-minute Apgar score was associated with an increased risk of death (odds ratio = 4.8). Grade 3 to 4 intracranial hemorrhage was a strong risk factor for cerebral palsy among survivors (odds ratio = 16.1), as was low 1-minute Apgar score (odds ratio = 2.9). Only 15% of cases of cerebral palsy in this study were associated with acidosis at birth.     

Interrelationships among abnormal cardiotocograms in labor, meconium staining of the amniotic fluid, arterial cord blood pH, and Apgar scores

A prospective study of the relationships among fetal heart rate pattern, meconium staining of the amniotic fluid, umbilical cord artery pH, and Apgar score was carried out in 1219 consecutive births. Interpretable cardiotocogram patterns and cord arterial pH and blood gas analysis were obtained in 698 cases. The sensitivity of an abnormal cardiotocogram at any time for acidosis (more than 1 SD below the mean, pH less than 7.17) was 80%, and for severe acidosis (more than 2 SDs below the mean, pH less than 7.085) was 83%. However, the predictive value was low, and 32% of fetuses had an abnormal cardiotocogram but no acidosis. If only cardiotocogram abnormality in the first stage of labor was considered, sensitivity was still 47% for acidosis and 67% for severe acidosis, and the false-positive rate was reduced to only 14%. We attempted to improve the prediction of acidosis by including meconium staining of the amniotic fluid, but 65% of the variation in umbilical cord artery pH and 72 and 86% of the variation in 1- and 5-minute Apgar scores, respectively, remained unexplained. In light of these poor correlations, the current practice of considering cardiotocogram abnormality, meconium staining of the amniotic fluid, acidosis, and low Apgar scores as indicating one single disorder, "fetal distress," is not valid.     

Outcome of fetuses with lactic acidemia

Umbilical arterial lactate, pH, PO2, PCO2, and base deficit were measured at delivery of 468 live-born infants. The correlation between the 1-minute Apgar score and lactate (r = -0.34) was comparable to that between the 1-minute Apgar score and pH (r = 0.30). The multiple correlation coefficient between the 1-minute Apgar score and all five parameters combined (lactate, pH, PO2, PCO2, and base deficit) was 0.36. This was not significantly higher than the simple correlation coefficient for pH alone (0.30). Similar correlation coefficients were noted for the 5-minute Apgar score. The dividing point between normal and pathologic lactate levels was 3.70 mmol/L. A pH less than 7.20 and a lactate level greater than or equal to 3.70 mmol/L had the same sensitivity, specificity, and positive and negative predictive values for low Apgar scores (less than 7). While pH and lactate are equally correlated with fetal outcome, their combination with each other and with other blood gas parameters does not predict outcome better than either pH or lactate alone.     

Value of observation of fetal breathing activity in antenatal assessment of high-risk pregnancy

While observation of fetal breathing movements has been used in fetal assessment, quantitative parameters (percent time spent in breathing [incidence], breath rate, or breath rate variability) have not been adequately evaluated as predictive tools. We examined 283 patients with high-risk pregnancies between 32 and 42 weeks' gestation and correlated their fetal breathing movement parameters with the rates of perinatal mortality, intrapartum fetal distress, neonatal acidosis, low 5-minute Apgar score, and intrauterine growth retardation. Fetal breathing data from standardized 60-minute biophysical tests were analyzed and compared with our institutional standards. Parameter values greater than 2 SD from the means of a previously studied normal population were considered abnormal. Whereas no individual parameter was a highly accurate predictor of adverse outcome, a fetal breathing movement incidence of less than 5% provided the best cutoff for diagnostic accuracy. Seventy percent of fetuses with 30 minutes of apnea had normal outcomes, whereas abnormally high breath rates (greater than 60 breaths/min) and low breath rates (less than 33 breaths/min) occurred with equal frequency among normal and pathologic fetuses. Breath interval variability was of no benefit in detecting fetuses with poor outcomes. Observation of fetal breathing movement incidence appeared to be most effective in pregnancies complicated by chronic hypertension and least effective in those with preeclampsia.     

Meconium aspiration and fetal acidosis

Meconium in labor is associated with increased perinatal morbidity and mortality. To identify the infants at risk, 53 women with moderate-to-thick meconium were followed in labor after obtaining baseline fetal scalp blood pH levels. Although 28 of the newborns (53%) exhibited an arterial cord pH of less than 7.25 at delivery, there were no significant predictive variables found in the electronic fetal monitoring score, Apgar score, or mode of delivery. Nine of the infants with a pH value of less than 7.25 had meconium below the vocal cords at delivery, but none in the infants with pH levels greater than or equal to 7.25. The P50 value for cumulative acidosis is 55 minutes, indicating a more rapid deterioration than an average-for-gestational-age fetus without meconium. Therefore, the presence of thick meconium implies that fetal stress must be avoided during labor, and early intervention is warranted when there is deviation from normal labor progress or fetal heart rate pattern.     

Nuchal cord in post-term pregnancy - relationship to suspected intrapartum fetal distress indicating operative intervention

Color Doppler Ultrasound was performed on 202 post-term pregnancies to detect the presence of a nuchal cord. A nuchal cord was diagnosed if the umbilical cord could be followed 360 degrees around the fetal neck. The results were not disclosed to the managing obstetrician, midwife, and patient. The perinatal outcome was analyzed according to Apgar score, umbilical cord artery and vein pH and base excess (BE), perinatal death, cesarean section, operative delivery for fetal distress (ODFD) and admission to neonatal intensive care unit (NICU). A nuchal cord was detected in 69 patients (34.2%). The incidence was not affected by parity or reduced amniotic fluid volume. There was no statistically significant increased risk for 1- and 5-min Apgar scores <7, umbilical artery pH <7.1, umbilical vein pH <7.20, umbilical artery base excess <-11, umbilical vein base excess <-11, perinatal death, cesarean section, ODFD or admission to NICU. Nuchal cord in post-term pregnancies is not associated with an increased risk for signs of fetal distress and operative intervention during labor and delivery.     

Apgar scores and umbilical arterial pH in preterm newborn infants

One- and five-minute Apgar scores and umbilical cord arterial pH values were compared in preterm newborn infants of various gestational ages. The more premature the infant, the more likely the Apgar score was low in the presence of a pH greater than or equal to 7.25. Conversely, the closer to term, the more frequently an infant with a pH of less than 7.25 had an Apgar score of greater than or equal to 7. Therefore, in preterm infants, there is little congruity between the Apgar score and umbilical cord pH. Based on these findings, it is not appropriate to label preterm newborn infants as asphyxiated based on a low Apgar score.     

The relationships among the fetal biophysical profile, umbilical cord pH, and Apgar scores

The relationships among the fetal biophysical profile, umbilical cord blood pH, and Apgar scores were investigated in 124 patients undergoing cesarean section before the onset of labor. Based on a standard for the diagnosis of fetal acidosis of an umbilical cord arterial pH less than 7.20, the sensitivity, specificity, and positive and negative predictive values of the fetal biophysical profile score were 90%, 96%, 82%, and 98%, respectively. When the combination of a nonreactive nonstress test and absent fetal breathing was used as the "abnormal test," the sensitivity, specificity, and positive and negative predictive values were 100%, 92%, 71%, and 100%, respectively. The efficacy of the fetal biophysical profile to indicate fetal acidosis was found to be superior to the 1- and 5-minute Apgar scores in sensitivity and positive predictive value. These data suggest that the biophysical profile is very accurate in the identification of the fetus with acidemia. The first manifestations of fetal acidosis are nonreactive nonstress testing and loss of fetal breathing; in advanced acidemia fetal movements and fetal tone are compromised. A new protocol of antepartum fetal evaluation is suggested based on individual biophysical components rather than the score alone.     

The significance of increasing umbilical artery systolic-diastolic ratios in third-trimester pregnancy.

OBJECTIVE: To evaluate the clinical significance of a marked increase in the systolic-diastolic ratios (S/Ds) of the umbilical artery (UA) Doppler velocity waveforms of third-trimester fetuses. METHODS: We evaluated 552 pregnancies at risk for placental insufficiency. Each patient had at least five successive weekly UA Doppler velocimetry studies between 32-42 weeks and a highest S/D within the normal range for gestational age. The S/D was considered markedly increased if it was at least 20% higher than the mean of four previous values. Clinical end points reviewed included mortality, fetal distress, 5-minute Apgar score below 7, metabolic acidosis, and neonatal intensive care unit (NICU) admissions for reasons other than prematurity. RESULTS: The S/Ds were normal in 478 patients and were markedly increased in 74. The two groups were similar in mean gestational age at testing and delivery and in the rates of fetal growth retardation and low 5-minute Apgar scores. The group without increased S/Ds had a higher mean birth weight and lower incidences of perinatal death, cesarean delivery for fetal distress, acidosis, and NICU admission. The overall sensitivity (43%), specificity (90%), positive predictive value (27%), and negative predictive value (95%) were similar to our previous experience in which we used a criterion of S/D above the 90th percentile. CONCLUSION: Marked increases in UA S/Ds, even if within an institutional "normal" range, may indicate a fetus at increased risk of compromise.     

Prediction of neonatal state by computer analysis of fetal heart rate tracings: the antepartum arm of the SisPorto multicentre validation study

OBJECTIVE: To evaluate the capacity of computer analysis of antepartum cardiotocographs performed by SisPorto 2.0 in predicting neonatal outcome. STUDY DESIGN: A prospective observational study was conducted in eight tertiary care centres in Europe and Australia, involving pregnant women in the absence of labor, scheduled for elective caesarean section, whose last fetal heart rate (FHR) tracing was performed within 4h of delivery. After exclusion of fetal malformations, multiple pregnancies, tracings with less than 30 min, tracings with more than 15% signal loss, difficult fetal extractions, and anesthesia complications, a total of 345 cases were analyzed. Computer quantification of cardiotocographic parameters was compared with newborn Apgar score, umbilical artery pH, metabolic acidosis and neonatal hypoxic-ischemic encephalopathy, by means of receiver operating characteristic (ROC) curves. RESULTS: Acceleration number, mean short-term variability, percentage of abnormal short-term variability and percentage of abnormal long-term variability had an excellent discriminative capacity to predict 1-min Apgar scores under or equal to 4 (areas under the ROC curve 0.96-1.00). The same parameters showed a slightly lower capacity to predict 5-min Apgar scores under or equal to 6 (areas under the ROC curve 0.81-0.89). The best cut-off values for these parameters, derived from the previously referred calculations, detected all cases of hypoxic-ischemic encephalopathy (n = 2). Cardiotocographic parameters showed a lower discriminative capacity in prediction of umbilical artery pH <7.20 (maximum area under the ROC curve 0.66) and <7.15 (maximum area under the ROC curve 0.69). CONCLUSIONS: Computerized quantification of accelerations and variability in the antepartum allows a good prediction of 1 and 5-min Apgar scores, and to a much lesser degree umbilical artery pH.     

Deceleration/contraction ratios as an index of fetal health during labor.

Internal FHR tracings of 259 patients with variable decelerations and 49 with late decelerations were analyzed for frequency and severity of the pattern in an attempt to correlate with fetal pH or Apgar score at 1 minute. A significant increase in the risk of fetal acidosis was associated with a frequency of greater than 30% variable decelerations and 20% late decelerations. It also increased with the increase of severity of the pattern. Variable decelerations are not good predictors of Apgar scores less than or equal to 6 at 1 minute, but late decelerations are predictive when they occur more than 20% of the time. The fetus with variable decelerations a normal pH can be observed through the first stage of labor with a high degree of confidence. However, when a 20% or more moderate-to-severe late deceleration/contraction ratio is present, intervention is necessary even if scalp blood pH is normal. The FHR deceleration/uterine contraction (UC) ratio is a simple bedside technique for assessing fetal outcome.     

Plasma volume, umbilical artery Doppler flow, and antepartum fetal heart testing in high-risk pregnancies

The purpose of this clinical study is to investigate the diagnostic value of plasma volume (PV), nonstress test (NST), contraction stress test (CST), and umbilical artery Doppler (UAD) in detecting fetal compromise in 81 patients (83 fetuses) at risk for fetal growth retardation. Neither PV nor UAD studies were used in the clinical management. There were two stillbirths and three neonatal deaths for a perinatal mortality of 6%. Twenty-seven infants (32.5%) were small for gestational age (SGA), seven (8.6%) had cord pH 7.20 or less, and five (6.2%) had 5-minute Apgar scores less than 7. Overall, PV had the highest sensitivity and NST the highest specificity regarding delivery of SGA infants. The positive and negative predictive values for infants with low cord pH and low Apgar scores were similar among the various tests. There were nine fetuses with zero or reverse diastolic flow: seven were SGA (four perinatal deaths) and all of them had both nonreactive NST and positive CST. The other two infants were appropriate for gestational age with all other tests being normal. Antepartum fetal heart rate testing appears to be similar to other tests in predicting poor fetal outcome in high-risk pregnancies.     

Submucous paracervical blockade compared with intramuscular meperidine as analgesia during labor: a double-blind study

A double-blind study was carried out to compare the effect of submucous paracervical blockade using 12 mL 0.25% bupivacaine (55 women) to the effect of intramuscular injection of 75 mg meperidine (62 women) during the first stage of labor. All 117 were normal primiparous pregnancies. Seventy-eight percent of the women in the paracervical blockade group achieved full or acceptable pain relief against 31% in the meperidine group (P less than .01). Transient fetal bradycardia occurred in two cases in the paracervical blockade group and one in the meperidine group; all infants were born in good condition. Fetal distress, defined as an umbilical artery pH of 7.15 or less and/or a one-minute Apgar score of 7 or less was more frequent in the meperidine group (16 infants) than in the paracervical blockade group (six infants) (P less than .05). Submucous paracervical blockade is superior to intramuscular meperidine as pain relief during labor. Furthermore, meperidine results in more infants with asphyxia as compared with paracervical blockade.     

The relation between Apgar score and subsequent developmental functioning

A randomly selected sample of 252 infants aged 5--18 months was evaluated through medical and developmental examinations. Developmental achievement scores and factors such as management of delivery and fetal distress were studied in relation to Apgar scores. Low-Apgar-score infants aged 5--8 months achieved consistently lower scores on all developmental fields. High-Apgar-score infants at younger and older ages did not differ on their achievement scores. Low Apgar score was much more frequent in infants delivered by vacuum extraction than in those delivered spontaneously, with forceps or by cesarian section. The frequency of low Apgar score was higher when fetal distress occurred.     

Comparison of umbilical artery pH and 5-minute Apgar score in the low-birth-weight and very-low-birth-weight infant

The division between "normal" and low Apgar scores is based largely on data obtained from term newborns and may not apply to the premature infant. Umbilical artery pH has been suggested as a better indicator of intrapartum asphyxia. We examined the charts of 558 infants with birth weights less than or equal to 2500 gm with respect to umbilical artery pH, 5-minute Apgar scores, and birth weight percentiles. A positive correlation between birth weight and 5-minute Apgar score was noted. No such relationship existed between birth weight and umbilical artery pH. Within birth weight groups, small-for-gestational-age infants have higher Apgar scores and lower umbilical artery pH values than their appropriate-for-gestational age counterparts.     

Subclassification of small-for-gestational-age fetus using fetal Doppler velocimetry

Our purpose was to determine whether small-for-gestational-age (SGA) fetus can be divided to subclassified groups using fetal Doppler velocimetry. Fifty-four pregnant women with SGA infant delivered after 37 weeks of gestation were studied. After 24 weeks of gestation, fetal middle cerebral artery puslatility index (MCAPI) and umbilical artery pulsatility index (UAPI) were measured at 2- to 3-week intervals using Doppler ultrasound. Perinatal outcomes [operative delivery due to fetal distress, abnormal fetal heart rate (FHR) pattern, meconium staining, low Apgar score (<7), neonatal acidosis (umbilical artery blood pH <7.15), neonatal intensive care unit (NICU) admission due to neonatal asphyxia, and decreased amniotic fluid] were compared in subclassified SGA groups using fetal Doppler velocimetry. The number of SGA fetuses with normal MCAPI and UAPI (normal SGA group) was 39, and those with significantly low MCAPI but normal UAPI (eventful SGA group) 15, respectively. Birth age and birth weights in the eventful SGA group were significantly earlier and lower than those in the normal SGA group, respectively (p < 0.05, and p < 0.005). There were significant increases in operative deliveries, abnormal FHR patterns and decreased amniotic fluid in eventful SGA group, when compared with events related to normal SGA group. However, there were no significant differences in meconium staining of amniotic fluid, low Apgar score, neonatal acidosis, and NICU admission between the two groups. These results suggest that SGA fetus with abnormally low MCAPI but normal UAPI has more poor perinatal outcomes, compared with that with normal MCAPI and UAPI.     

Routine umbilical cord blood gas determinations?

Between 1986 and 1988, 1924 term nulliparous patients with spontaneous onset of labor were studied to assess the importance of obtaining umbilical cord blood gas levels on all deliveries. The umbilical cord arterial and venous pH values (expressed as mean +/- 2 SD) were 7.24 +/- 0.14 (n = 1694) and 7.32 +/- 0.12 (n = 1820), respectively. The incidence of newborn depression (1- or 5-minute Apgar score less than 7) was 14.1%; of these depressed newborns, the incidence of normal umbilical cord arterial pH values (greater than or equal to -2 SD) was 77.8%. Of the vigorous newborns, there was a 2.1% incidence of umbilical cord arterial blood acidemia. Umbilical cord arterial blood acidemia in vigorous newborns was not highly predictive of specific morbidity in the immediate newborn period. Regression analysis demonstrated the umbilical cord arterial pH to correlate best with the Apgar scores when compared with all other arterial or venous blood gas measurements. We reached the following conclusions: (1) that obtaining cord arterial pH values in vigorous newborns should be considered since the values will provide objective documentation or normal fetal acid base balance in 98% of infants. (2) Only a cord arterial pH determination is recommended since it reflects fetal or newborn status more accurately than all other measurements. Additional measurements increase the likelihood of abnormal results and do not contribute to neonatal management. (3) An umbilical cord blood pH value is extremely useful in ruling out the diagnosis of birth asphyxia in the depressed newborn.     

Fetal distress and the condition of the newborn using cardiotocography and fetal blood analysis during labour

The efficacy of electronic fetal monitoring combined with fetal blood analysis during labour in identifying fetal distress was investigated in a retrospective study. Operative delivery for fetal distress diagnosed during labour was performed in 9% of 2659 deliveries. All had continuous fetal heart rate monitoring and 22% had a fetal scalp blood analysis. Operative delivery had been performed in 53% of the infants who were acidotic at birth (umbilical artery pH less than 7.20) and in 46% of those with a low modified Apgar score (less than 7). These results show that the use of continuous fetal heart rate monitoring and fetal scalp blood sampling detects fetal distress without resulting in a high rate of operative delivery.