Catecholamine abnormalities in transient tachypnoea of the premature newborn.

The aim of the present study was to assess if there was an association between low catecholamine levels at birth in the premature infant and the development of TTN. Blood samples were collected at delivery from the umbilical artery of all preterm infants with a gestational age less than 36 weeks for determination of pH and catecholamine levels (noradrenaline and adrenaline). Amongst non-asphyxiated infants only, cord pH greater than 7.25 and/or Apgar score greater than 7 at five minutes, catecholamine levels were compared between the 10 infants who developed transient tachypnoea of the newborn (TTN) and 13 controls of a similar gestational age range (31-35 weeks) who developed no respiratory distress in the neonatal period. Infants who developed TTN were more often delivered without labour, 8 of 10 compared to 2 of 13 controls (p less than 0.01). There were no significant differences in adrenaline levels between the two groups. Noradrenaline levels, however, were significantly lower in the infants who developed TTN, being a median of 3.1 nmol/l (range 1.07-5.85 nmol/l) compared to a median of 6.4 nmol/l (range 2.38-22.83) in the controls (p less than 0.01). Infants who were delivered following labour had significantly elevated noradrenaline levels compared those delivered without labour (elective delivery) (p less than 0.05). These results suggest that low noradrenaline levels in preterm infants may explain the association in this group of TTN and "elective" delivery.     

Umbilical artery acid-base status in the preterm infant

It is becoming increasingly apparent that Apgar scores are generally lower in otherwise uncomplicated preterm newborns than in term newborns. However, there is little information regarding normal values for umbilical artery blood gas measurements in the preterm infant. The present study included 77 otherwise uncomplicated preterm infants and 1292 uncomplicated term infants. Although preterm infants did have significantly lower 1- and 5-minute Apgar scores, there was no significant difference in the frequency of acidemia (umbilical artery pH below 7.20). The mean pH was 7.29 in preterm infants and 7.28 in term infants. Mean values for pCO2, pO2, HCO3, and base deficit were similar in each group. There were no significant differences in umbilical artery blood gas values in the 77 preterm infants according to birth weight groups. Umbilical cord blood acid-base determination may prove a useful adjunct in assessing the condition of the newborn preterm infant.     

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.     

Diagnosis of birth asphyxia on the basis of fetal pH, Apgar score, and newborn cerebral dysfunction

Imprecise diagnosis of birth asphyxia coupled with uncertainties about causal factors for neurologic abnormalities in the newborn have greatly fueled the current litigation crisis in obstetrics. Our goal was to more precisely define birth asphyxia based on fetal condition as measured by umbilical artery blood pH, Apgar scores, and neurologic condition of newborns. We selected for study 2738 patients with singleton pregnancies with cephalic presentations who were delivered of infants at term to avoid complications such as prematurity, which may affect infant outcome independent of birth condition. The basis for study of these particular patients were defined criteria for high risk and an indicated arterial cord pH value. A total of five infants demonstrated cerebral dysfunction as evidenced by seizures during the neonatal period. Infection was linked to seizures in three of these infants; one infant had neonatal asphyxia and only one infant's clinical course could be attributed solely to birth events (uterine rupture). Stratification of umbilical artery blood pH values, Apgar scores, and combinations of these dependent variables in relation to newborn clinical outcomes revealed that infants must be severely depressed at delivery before birth asphyxia can be reliably diagnosed. Such depression includes Apgar scores less than or equal to 3 at 1 and 5 minutes plus umbilical artery pH values less than 7.00.     

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.     

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.     

The relationship between Apgar score, umbilical artery pH and operative delivery for fetal distress in 2778 infants born at term

A total of 2778 infants born at term were studied to determine the relationship between Apgar scores after 1 min, umbilical artery pH values, mode of delivery, a diagnosis of fetal distress leading to operative delivery, and sex. Eighty-three percent of the population had normal Apgar scores (greater than or equal to 8) and normal pH values (greater than 7.15) in which 10% were operatively delivered for fetal distress (ODFD). Sixty-one percent of the children with low Apgar scores (less than or equal to 7) had normal pH values, and 74% of the infants with acidosis (pH less than or equal to 7.15) had normal Apgar score. Twenty-four percent of the infants with a low Apgar score and/or acidosis were ODFD (sensitivity). Ninety percent of the infants who had Apgar scores and pH values were not ODFD (specificity). The predictive value (a low Apgar score and/or acidosis) of ODFD was 33%, and the negative predictive value (normal Apgar score and a normal pH) of ODFD was 85%. A significantly higher incidence of ODFD and acidosis was found in boys.     

Fetal catecholamines and the Apgar score

The association between Apgar score, pH and catecholamine levels was investigated in 181 newborn infants with a gestational age between 29 and 43 completed weeks. Umbilical arterial blood was obtained before the first breath with the double clamp technique and pH was measured. Plasma adrenaline and noradrenaline were analyzed by high performance liquid chromatography. The Apgar score at 1 minute was above or equal to seven in 167 infants. Forty-four per cent of these infants had pH below 7.25. A negative correlation between log noradrenaline and pH (r = 0.52, p less than 0.001) and between log adrenaline and pH (r = 0.40, p less than 0.001) was found. In 14 infants the Apgar score was below seven. The median pH was 7.21 (range 7.02-7.32). Also in this group a negative correlation between log noradrenaline and pH (r = 0.60, p less than 0.05) and between log adrenaline and pH (r = 0.77, p less than 0.01) was noted. We concluded that the Apgar score is an insufficient measure of fetal asphyxia defined as fetal acidosis but rather reflects the vitality of the newborn.     

Neonatal complications at term as related to the degree of umbilical artery acidemia

The degree of umbilical arterial acidemia associated with immediate newborn morbidity has not been determined. Therefore we compared 358 term infants with umbilical artery acidemia (pH less than 7.20) with 358 term, nonacidotic matched control infants, to evaluate immediate neonatal complications in both groups. Nonacidotic was defined as an umbilical artery pH greater than or equal to 7.20. Complications included seizures, persistent hypotonia, and/or signs of end-organ damage such as renal or cardiac dysfunction. None of the 693 newborns with an umbilical artery pH greater than or equal to 7.00 had such complications. Two of 23 infants with an umbilical artery pH less than 7.00 had sequelae related to intrapartum asphyxia. In these two infants the umbilical artery pH was less than 7.00, the 1-minute and 5-minute Apgar scores were less than or equal to 3 and the acidemia was metabolic in nature.     

Umbilical cord pH and base excess values in relation to neonatal morbidity for infants delivered preterm

OBJECTIVE: Our purpose was to determine the relationship/predictive value of umbilical cord pH and base excess (BE) values to adverse neonatal outcomes for preterm infants. STUDY DESIGN: A tertiary center perinatal/neonatal database was used to obtain umbilical cord pH and BE values, adverse neonatal outcomes, and patient demographics for preterm (PT, 32-36 weeks gestational age) and very preterm (VPT, 25-32 weeks gestational age) singleton live-born infants delivered between November 1995 and March 2002. RESULTS: PT (n=1807) and VPT (n=603) groups demonstrated a significant inverse curvilinear relationship of umbilical cord pH and BE values to Apgar score <7 at 5 minutes, respiratory distress syndrome, assisted ventilation, and intraventricular hemorrhage/periventricular leukomalacia. Receiver operating characteristic area under the curve values ranged from 0.69 to 0.86 (PT) and 0.70 to 0.87 (VPT). There was little difference between umbilical vein, umbilical artery, pH, or BE in predictive value. CONCLUSION: Umbilical cord pH and BE are related to subsequent adverse outcome events for infants delivered preterm. Worsening acidosis is associated with progressively greater increases in these outcomes with no discriminatory value within or between umbilical artery and umbilical vein pH and BE.     

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.     

Association between umbilical artery cord pH, five-minute Apgar scores and neonatal outcome.

A prospective study was conducted of 270 intrapartum patients admitted in labor to investigate the independent and combined relationships between umbilical arterial cord pH and Apgar scores and neonatal outcome. The results revealed that when assessed independently, a low 5-min Apgar score (less than 7) was associated with both NICU admission and neonatal sepsis. When categorized by both cord pH and 5-min Apgar, the majority of patients (75.9%) had both parameters normal, 20.7% had an abnormal pH (less than 7.20) and normal Apgar (greater than or equal to 7) and few patients had either both normal or an abnormal Apgar given a normal pH. Given a normal 5-min Apgar score, additional information about the cord pH did not enhance the predictability for either NICU admission or neonatal sepsis. Neonates with both an abnormal pH and 5-min Apgar had the highest incidence of NICU admission. For all neonates, the presence of meconium greatly increased the likelihood of being admitted to the NICU.     

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.     

The effect of preterm birth on umbilical cord blood gases.

Apgar scores are used routinely to assess early neonatal status, but are less accurate in the preterm neonate because of developmental immaturity. Attention has been directed to umbilical cord gases as a method of neonatal evaluation. Using a retrospective chart review of all viable preterm births (24-36 weeks' gestation) between January 1986 and December 1989, we tabulated the umbilical cord gas indices of these infants. Fetuses with lethal congenital anomalies and those with abnormal heart rate tracings on admission were excluded from the data base, leaving 1872 infants. Cord arterial blood gas values were available for analysis in 74.4% of cases and cord venous gas values in 81.8%. The mean (+/- standard deviation [SD]) arterial and venous umbilical cord blood gas values for the preterm infants, were, respectively: pH, 7.26 +/- 0.08 and 7.33 +/- 0.07; oxygen pressure, 19.0 +/- 7.9 and 29.2 +/- 9.7 mmHg; carbon dioxide pressure, 53.0 +/- 10.0 and 43.4 +/- 8.3 mmHg; bicarbonate, 24.0 +/- 2.3 and 22.8 +/- 2.1 mEq/L; and base excess, -3.2 +/- 2.9 and -2.6 +/- 2.5 mEq/L. Acidemia was defined statistically as 2 SDs or more below the population mean. The incidence of 5-minute Apgar scores below 7 in the preterm infants was 8.5% and within this group, 17.8% were acidemic (arterial pH 7.10 or lower). More than 82% of neonates with 5-minute Apgar scores less than 7 had normal umbilical cord blood gases. There was no significant difference in umbilical arterial blood gas values between preterm infants and 1924 term deliveries at our institution between 1986-1988.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Fetal acidosis and the abnormal fetal heart rate tracing: the term breech fetus

The intrapartum fetal heart rate tracings of 27 terms fetuses in breech presentation were analyzed to evaluate their immediate neonatal outcome. The tracings were quantitatively evaluated for comparison with Apgar scores and umbilical cord gases at delivery. Of the 27 cases, 12 had monitoring strips that scored 4 or less before birth. The P50 for acidosis at delivery (an umbilical artery pH of 7.25 or less) was 55 minutes for an intrapartum tracing that scored 4 or less. Fetuses with intrapartum tracings scoring 8 or more throughout labor had normal Apgar scores and cord gases. In comparing the present data with those of a previous study of vertex presentations, the authors found that given similar tracings, the breech fetus deteriorates more rapidly than the vertex fetus. Cesarean section is recommended if delivery is not imminent in a laboring breech and the intrapartum tracing deteriorates to score 4 or less.     

ACOG Committee Opinion. Number 333, May 2006 (replaces No. 174, July 1996): The Apgar score

The Apgar score provides a convenient shorthand for reporting the status of the newborn infant and the response to resuscitation. The Apgar score has been used inappropriately to predict specific neurologic outcome in the term infant. There are no consistent data on the significance of the Apgar score in preterm infants. The Apgar score has limitations, and it is inappropriate to use it alone to establish the diagnosis of asphyxia. An Apgar score assigned during resuscitation is not equivalent to a score assigned to a spontaneously breathing infant. An expanded Apgar score reporting form will account for concurrent resuscitative interventions and provide information to improve systems of perinatal and neonatal care.     

Gestational age-dependent reference values for pH in umbilical cord arterial blood at term

OBJECTIVE: Despite a change of fetal physiologic and biochemical functions with gestational age, stationary umbilical cord acid-base reference values are used as measures of obstetric care quality. The aim of this study was to assess the risk of low Apgar score relative to low pH when using stationary versus gestational age-adjusted reference values. METHODS: Umbilical artery pH was determined in 24,390 term singleton vaginal deliveries with a 5-minute Apgar score of 9 or greater. Low pH was defined as less than 7.10 as a stationary cutoff value, whereas pH less than (mean - 2 standard deviations [SDs]) was used when gestational age was considered. The 5-minute Apgar score less than 7 at low pH was studied in 44,978 term deliveries. RESULTS: A significant negative correlation was found between gestational age and umbilical artery pH. The odds ratio (OR) for pH less than 7.10 was continuously increasing, from 0.6 at 37 weeks to 1.5 at 42 weeks. In contrast, the OR for pH less than (mean - 2 SDs) was steady until 42 weeks, whereafter it increased (OR 1.24; 95% confidence interval 1.05, 1.47). A linear decrease of the association between Apgar score less than 7 and pH less than 7.10 with increasing pregnancy duration was found (P =.097), but for pH less than (mean - 2 SDs) there was no such association. CONCLUSION: We found a physiologic linear decline of umbilical artery pH with gestational age at term. Gestational age-adjusted umbilical cord artery pH reference values result in fewer diagnoses of cord acidemia than a stationary cutoff of pH less than 7.10.     

Correlation between neonatal Apgar scores and the results of maternal and umbilical cord blood gas analysis

The correlation between the Apgar scores of 162 neonatal 1 minute after birth and the result of maternal arterial and umbilical cord blood gas analysis was studied. The results were as follows: (1) With decreasing neonatal Apgar score, the value of the pH, PO2, HCO3, TCO2 and actual base excess (ABE) of the maternal arterial and umbilical cord blood also decreased markedly, while the PCO2, except that of the maternal arterial blood, increased obviously, and mixed acid base imbalance and hypoxemia also significantly increased (P less than 0.01). (2) Of the neonates with umbilical arterial blood pH less than or equal to 7.2, the proportion of neonates with Apgar score less than or equal to 3 amounted to 100%; that with on Apgar score of 4-7, was 77.7%; And that with on Apgar score of 8-10, was 56.31%. The difference was highly significant statistically (P less than 0.01).     

Monitoring arterial oxygen saturation in the neonate

Term neonates (N = 35) with an one minute Apgar score of greater than or equal to 8 and mean umbilical artery pH values within normal were monitored by pulse oximetry. SaO2 monitoring started one minute after delivery. The initial SaO2 ranged from 40 to 75%. Neonates with a SaO2 above 80% five minutes after delivery remained untreated, neonates with a SaO2 below 80% received mask CPAP (figure 1). The initial difference in SaO2 between the groups was statistically significant (p less than 0.05). Mean umbilical artery pH and one, five and ten minutes Apgar score values were statistically not significant between the groups (p greater than 0.05). CPAP had been terminated as soon as SaO2 had reached 90%. This had been the lowest value monitored in spontaneously breathing neonates one day after delivery. Our findings indicate that neonates may sustain prolonged periods of decreased SaO2 which had not been detected by umbilical artery pH nor by the Apgar score. SaO2 monitoring by pulse oximetry served as a valuable method in the immediate newborn evaluation.