Biochemical differences related to birth order in triplets

This is the first report to date on biochemical parameters in triplets. Umbilical artery and venous pH, PO2, PCO2, lactate and base deficit were measured in seven sets of triplets. Other parameters compared were route of delivery, one- and five-minute Apgar score, birth weight, relative birth order and sex. Twenty-one viable infants were born from three induced and four spontaneous pregnancies. Female: male sex ratio was 1.6:1.0. All triplets within a set were delivered by the same route--six sets by cesarean section and one set vaginally. There were no significant differences, according to Student's t-test, in birth weight, Apgar scores and biochemical parameters related to birth order. Comparison of umbilical artery and umbilical venous pH, PO2, PCO2, lactate and base deficit differences did not demonstrate evidence of acidosis or significant base deficit in the third triplet when compared with the first two, suggesting that the duration in utero after deliver of the firstborn is not associated with metabolic acidosis or hypoxia in the absence of any obstetric complication or anesthetic problem.     

Differences in twins: the importance of birth order

Despite the clinical impression that firstborn twins do better than second-born twins, recent reports have shown no difference in perinatal mortality between them. In order to evaluate differences in twins, more sensitive means than perinatal deaths are necessary. This study examines differences between 80 firstborn and second-born twin pairs with respect to Apgar score, umbilical venous and arterial blood gas, and acid-base data. The umbilical venous and arterial blood PO2, PCO2, base deficit, pH, and lactic acid concentration were measured in paired samples and compared with the paired t test and chi 2 when applicable. Statistically significant differences favoring twin A, the firstborn, were found in 1-minute Apgar score, umbilical venous pH, PO2, and PCO2, and umbilical arterial PO2. The other factors in umbilical venous and arterial blood did not show statistically significant differences. When these parameters were examined with respect to route of delivery, monochorionic and dichorionic twins, interval between twins, and vertex twins only, with the possible effects of malpresentation eliminated, the results persistently favored the firstborn twin. Thus it is unequivocally demonstrated that there are substantial differences at birth favoring the first twin, despite similar perinatal mortality for both. The data suggest that the second-born twin has potentially greater susceptibility to hypoxia and trauma.     

The Apgar score: is it enough?

One thousand thirty-two neonates were evaluated with umbilical venous and arterial blood samples drawn at delivery for assessment of pH, PO2, PCO2, and base deficit. These values were statistically correlated with Apgar scores in all of the neonates studied. Infants were divided into Apgar groupings (group A, greater than or equal to 7 at one and five minutes; group B, less than 7 at one minute, greater than or equal to 7 at five minutes; group C, less than or equal to 7 at both one and five minutes). Generally, umbilical artery and umbilical venous data were parallel. The differences in means for pH, PO2, PCO2, and base deficit was significant when group A was compared with group B in both umbilical artery and umbilical venous data. However, a severe degree of biochemical disturbance must take place before significant association with neonatal depression can be made. It appears that umbilical blood biochemical data are related to fetal metabolic status before birth but only modestly influence the one-minute Apgar score.     

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).     

Blood gases and acid-base status of the human second-trimester fetus

Maternal arterial, umbilical venous, and umbilical arterial blood were obtained at fetoscopy in the second trimester and analyzed for blood gases and acid-base indexes. In comparing umbilical venous (N = 31) with maternal arterial (N = 39) samples, the mean (+/- SD) PO2 was lower (55 +/- 7 versus 100 +/- 15 mmHg, P less than .001) and PCO2 (37 +/- 4 versus 34 +/- 4 mmHg), bicarbonate (20 +/- 2.0 versus 18.5 +/- 1.5 mmol/L), lactate (1.10 +/- 0.25 versus 0.80 +/- 0.30 mmol/L), and base excess (-4.2 +/- 2.3 versus -6.0 +/- 1.5 mmol/L) were higher (P less than .001). The mean umbilical venous pH did not differ significantly from the maternal arterial (7.358 +/- 0.040 versus 7.373 +/- 0.035). Comparing umbilical arterial (N = 21) with umbilical venous (N = 31) samples, the PO2 level was lower (34 +/- 4 versus 55 +/- 7 mmHg, P less than .001) and PCO2 higher (42 +/- 4 verus 37 +/- 4 mmHg, (P less than .001); the pH was marginally lower (7.339 +/- 0.03 versus 7.358 +/- 0.040; P less than .05) and bicarbonate higher (22 +/- 1.5 versus 20 +/- 2.0 mmol/L, P less than .001). Umbilical arterial and umbilical venous values were similar in the case of lactate and base excess.     

Asphyxial complications in the term newborn with severe umbilical acidemia.

OBJECTIVE: Our purpose was to determine the relationship of umbilical acid-base status and Apgar score to neonatal asphyxial sequelae in infants with severe acidemia (pH < 7.00). STUDY DESIGN: The obstetric and neonatal course of 129 term, nonanomalous singleton infants with umbilical pH < 7.00 was reviewed. RESULTS: There were three stillbirths (failed resuscitation). Seventy-two of 126 (57%) were admitted to the neonatal intensive care unit. Thirty-eight percent had pulmonary dysfunction, 26% renal dysfunction, 31% cardiac dysfunction, and 31% hypoxic ischemic encephalopathy (seizures and hypotonia, n = 29; seizures only, n = 3; hypotonia only, n = 10). There were five neonatal deaths. In 109 cases umbilical arterial values were available, and among these infants there was a significant increase in the incidence of seizures with declining pH from 9% (5/57), with a pH of 6.90 to 6.99, to 80% (8/10), with a pH of 6.61 to 6.70. Respiratory acidemia (PCO2 > 65, base deficit < 10) was identified in 28 of 109 (26%), all but six occurring in the pH range above 6.90. Compared with infants with comparable umbilical artery pH, infants with respiratory acidemia did not differ significantly with respect to asphyxial end-organ injury in general (8/35 vs 6/22), but there was a trend toward a lower incidence of hypoxic ischemic encephalopathy (6/35 vs 1/22, p = 0.06). All infants with definite abnormal outcome (five neonatal deaths and 10 severe neurologic deficit) had seizures, hypotonia, and at least one other organ system dysfunction. Twenty-four of 29 infants (83%) who developed seizures had a 5-minute Apgar score < 7, but only 12 of 29 (41%) had a 5-minute Apgar score of < or = 3. Two infants with Apgar scores of 6 and 7 at 5 minutes and no evidence of nonasphyxial comorbidity subsequently manifested profound neurologic deficit. CONCLUSIONS: Infants with severe umbilical acidemia can be separated with regard to risk of hypoxic ischemic encephalopathy and abnormal neurologic outcome by consideration of the severity and composition of the acidemia and evidence of other end-organ dysfunction. Even in this pH range the Apgar score is not highly predictive of asphyxial complications.     

Correlation of head-to-body delivery intervals in shoulder dystocia and umbilical artery acidosis

OBJECTIVE: Our goal was to determine the effect of shoulder dystocia on umbilical artery acidosis. STUDY DESIGN: We performed a retrospective analysis of 134 mother-infant pairs of shoulder dystocia cases at our institution from January 1, 1994, through December 31, 1997. Cases were identified from the obstetric database, and charts were abstracted for demographics, head-to-body delivery interval, umbilical blood gas parameters, and neonatal outcome. Pooled student t tests were used to compare mean blood gas values with data previously reported from our patient population. Regression analysis was performed regarding head-to-body delivery interval and blood gas parameters. RESULTS: The mean umbilical artery pH of shoulder dystocia cases (7.23 +/-.082) was less than the mean arterial pH of all vaginal deliveries in our institution (7.27 +/-.069), P <.001. Head-to-body delivery intervals (available for 44 cases) were not associated with statistically significant alterations in umbilical artery pH (r(2) =.0004), PCO(2) (r(2) =.011), or base deficit (r(2) =.006). Increasing head-to-body delivery interval was also not significantly correlated with decreasing 5-minute Apgar score (r =.0278). CONCLUSION: In our study population, shoulder dystocia resulted in statistically significant but clinically insignificant reductions in mean umbilical artery blood gas parameters. No statistically significant linear relationship was identified between the head-to-body delivery interval and fetal acid-base status.     

Acid-base status at birth and neurodevelopmental outcome at four and one-half years

Two hundred thirty term infants with measured acid-base status in umbilical arterial blood at birth were selected from 1210 consecutive deliveries for detailed neurodevelopmental follow-up at age 4 1/2 years; 203 were examined. Cutoff points approximately 1 SD from the mean (pH less than or equal to 7.10; base deficit greater than 12 mmol/L) were used to define acidosis. No statistically significant associations between acidosis and developmental outcome were found. The highest proportion of unimpaired children was found among those who were most severely acidotic at birth (pH less than or equal to 7.04; 2 SD below mean), but this finding was not statistically significant. These findings suggest that the ability of the fetus to produce an acidosis in response to the stress of labor may be beneficial to long-term outcome. The 10 nonacidotic babies with 1-minute Apgar scores of less than or equal to 3 showed statistically significant deficits in some areas. Coincident acidosis was not associated with a worse outcome for infants with low Apgar scores.     

Umbilical cord blood gases for term healthy newborns

Examination of paired umbilical arterial and umbilical venous blood gases for 147 term, healthy newborns revealed a strong correlation of pH, bicarbonate, and base excess with the 1-minute Apgar score. Although significantly different from each other, a strong correlation existed between the gas measurements of the two vessels. The lower limit of pH for the umbilical artery was 7.12 and for the vein, 7.25. The arterial-venous difference for bicarbonate but not pH, oxygen or carbon dioxide tension, or base excess was correlated with the 1-minute Apgar score.     

Intrapartum fetal asphyxia: study of umbilical cord blood lactate in relation to fetal heart rate patterns

Purposes

To correlate between umbilical artery cord blood lactate and acid–base status with intrapartum fetal heart rate monitoring, and to measure the reliability of umbilical cord blood lactate for prediction of early neonatal outcome.

Methods

Sixty-six participants with intrapartum abnormal fetal heart rate monitoring and 60 participants with normal intrapartum recordings were recruited. The abnormal recordings included late onset, atypical variable and simple variable decelerations. After delivery, the arterial cord blood lactate, pH, actual base excess (ABE), and Apgar score were measured in all participants.

Results

There was significant inverse correlation between cord lactate and pH and ABE in all participants (correlation coefficient = ?0.7, p < 0.0001). The cord lactate was significantly higher in the late onset and atypical variable decelerations groups compared to control (p < 0.0001). There was no significant correlation between the Apgar score and blood lactate in all groups; however, the sensitivity and specificity of cord lactate to predict low score at 5 min were higher in comparison to cord pH.

Conclusions

Umbilical cord blood lactate is a reliable marker for intrapartum fetal asphyxia compared to cord acid–base status with better prediction for newborns with low Apgar score.     

Intervalle de naissance entre les jumeaux : une limite de temps est-elle justifiée ?

OBJECTIVES: To assess the effect of the twin-to-twin delivery interval on the umbilical cord blood gas status and the neonatal outcome of the second twin following vaginal delivery. PATIENTS AND METHODS: Retrospective study of twin deliveries at or beyond 34 weeks of gestation over a period of five years. The correlation between the twin-to-twin delivery interval, and the umbilical arterial blood gas parameters of the second twin, including pH, PO(2), PCO(2), HCO(3-) and base excess, was studied. A second analysis was performed after exclusion of non-vertex presentation, need for general anesthesia, growth restriction and weight difference between the twin>30%. RESULTS: Two hundred and thirty-nine patients were studied. The mean twin-to-twin delivery interval was 11.3+/-6.4 minutes (between 6 and 14 minutes in 56.1% of cases). The second twin had more Apgar score<7 at 1 minute (P<0.02) and more arterial ombilical pH<7.20 (P<0.01) than the first twin. Over 15 minutes, the mean arterial pH was lower (P<0.01) and the number of arterial pH<7.20 increased (P<0.03). In contrast, the mean Apgar score and the rate of neonatal transfer did not differ significantly. There were significant negative correlations between arterial pH, base excess and bicarbonates and the twin-to-twin delivery interval (P<0.05). Similar results were found in the homogenised population. The reduction in the second twin arterial pH was expressed as pH=7.282-0.003 x time. DISCUSSION AND CONCLUSION: Umbilical cord arterial blood gas parameters deteriorate with increasing twin-to-twin delivery interval. Our results suggest that this interval should be less than 15 minutes, but obstetrician should adapt to every clinic situation.     

Acidosis in newborns with nuchal cords and normal Apgar scores.

OBJECTIVE: Apgar scores and cord blood gases (BG) and pH were compared between a group of babies with nuchal cords and a group without nuchal cords and uncomplicated deliveries. STUDY DESIGN: We collected umbilical arterial (UA) and umbilical venous (UV) blood samples from the placentas of term infants from both normal deliveries (NORM, n=29) and nuchal cords (NUCH, n=33). BG/pH and hematocrit were measured; base deficits and oxygen contents were calculated; and a member of the study assigned Apgar scores and demographic data were collected from the babies' charts. RESULTS: Median Apgar scores in the NUCH babies at 1 and 5 minutes were 9 and 9 respectively, which did not differ from the NORM infants. The pH, PCO(2), and oxygen content obtained from UV of the NUCH infants was not statistically different from the NORM. The pH and oxygen content of the NUCH UA was significantly lower than that of the NORM. The UA PCO(2) in the NUCH was greater than the NORM. Veno-arterial (VA) differences (Delta VA) in pH and PCO(2) of the NUCH infants were greater than that of the NORM. CONCLUSION: The Apgar score is not a sensitive indicator of acid-base changes in nuchal cord patients; UV samples alone may be misleading. UA must be sampled to detect the hypercapnia and diminished oxygen content that is a result of the nuchal cord.     

Maternal posture in second stage and fetal acid base status

The effect of position during the second stage on outcome was studied in 58 women, with no exclusions because of pregnancy complications or signs of fetal distress, who were randomly allocated to have the second stage conducted in either the dorsal or 15 degrees lateral tilt position. All the women were of parity 0 or 1 and the two groups were well matched except for gestational age at delivery. There were no differences in clinical outcome between the two groups, but overall the dorsal group had lower cord artery pH values (P less than 0.05), higher PCO2 (P less than 0.01) and a greater base deficit, but not significantly so. pH and base deficit were similar in both groups where the second stage did not last greater than 15 min. Thereafter, there was a trend to decreasing pH and increasing base deficit with increasing length of second stage in the dorsal group, but not in the tilt group though this did not reach statistical significance. Low Apgar scores, complicated pregnancy and first pregnancy were each associated with significantly lower pH levels. Prolonged placement of the patient in the flat dorsal position should be avoided in second stage, though a suitable alternative under the conditions described has not been defined.     

Approximate entropy, a statistic of regularity, applied to fetal heart rate data before and during labor.

OBJECTIVE: To determine whether approximate entropy (ApEn), a new statistic of regularity, when applied to fetal heart rate (FHR) data antepartum or in labor, would offer an advantage over standard statistics of variation in predicting outcome. METHODS: A large data base of antepartum FHR records collected in clinical practice over 10 years was available. Two data sets in labor were stored on disk in small computers interfaced to fetal monitors on-line. Outcomes were assessed using blood gas values on delivery and Apgar scores. RESULTS: Antepartum, when the most favorable form of ApEn was used on 769 good-quality FHR records, the correlation with measurement of short-term variation was high. This was especially true when the fetal pulse interval variation fell below the normal range (less than 6 milliseconds short-term; r = 0.93) and in 20 other records with sinusoidal variation (r = 0.96). Approximate entropy varied with fetal sleep cycles and took longer to calculate than FHR variation. During the last hour of labor, in 319 records, there was no significant correlation between umbilical artery base deficit values on delivery and ApEn measurement. In 871 additional good-quality records of fetuses with normal outcome, the mean (+/- standard error [SE]) ApEn (0.95 +/- 0.005) was significantly greater than in 22 records (0.88 +/- 0.028) from fetuses with abnormal outcome (umbilical artery base deficit more than 12 mmol/L and Apgar score of 3 or less at 1 minute). However, consideration of the frequency distributions of these measurements showed that ApEn did not discriminate between normal and abnormal outcomes. The SD of fetal pulse intervals rose in labor whereas ApEn values fell, confirming that this new statistic of regularity differs from standard statistics of variation. CONCLUSION: Approximate entropy offered no advantage over measurement of short-term FHR variation antepartum, and neither measurement predicted outcome in labor.     

The Northwestern University triplet study. IV. Biochemical parameters

Umbilical arterial and venous blood gas indices of 11 triplet pregnancies were reviewed. Ten sets of triplets were delivered by cesarean section and one set was delivered vaginally. Mean 1-minute Apgar scores were significantly lower in the group of infants delivered third than in either of the other birth order groups. There were no statistically significant differences when the mean umbilical arterial or venous pH, PCO2, and base deficit were compared among any one triplet and the other two. Similarly, no significant differences were found when these parameters were compared by birth order in relation to mean 5-minute Apgar scores, mean birth weights, and mean gestational ages at delivery. Birth order did not appear to significantly influence acid-base status, although it may become significant with an increasing time in utero after delivery of the firstborn infant. Further study is necessary to investigate whether there is a critical interval of delivery whereby the infants remaining in utero become acidotic.     

Screening with Doppler velocimetry in labor

Doppler flow velocimetry was performed on 273 nonselected patients in labor. All patients were at least 2 cm dilated and 80% effaced (58% greater than 4 cm) and were delivered of infants within 24 hours. Fetal heart rate tracing performed at the same time was read by another observer and compared with Doppler flow velocity measurements (systolic/diastolic ratio, pulsatility index). A significant correlation was noted (r = 0.234, p less than 0.001) between the two modalities. Both fetal heart rate tracings and umbilical flow velocity measurements were correlated with fetal outcome. Significant associations were noted between the umbilical systolic/diastolic ratio and fetal distress. 5-minute Apgar scores, the need for intubation independent of gestational age, and umbilical arterial cord pH and base excess. It appears that the information obtained from flow velocimetry had additional benefits compared with that of fetal heart rate tracings alone.     

Umbilical artery blood gas parameters in neonates with early onset seizures who die

OBJECTIVE: To relate umbilical artery blood gas parameters to mortality among neonates with hypoxic-ischaemic encephalopathy related to early onset seizures. DESIGN: Population cohort study. SETTING: British Columbia Women's Hospital. POPULATION: Forty-seven infants at >or=32 weeks of gestation admitted to NICU with early onset seizures secondary to hypoxic-ischaemic encephalopathy with umbilical artery blood gases done at delivery. METHODS: Patients were divided into two groups: (1) Infants with neonatal seizures who survived, and (2) infants with neonatal seizures who died related to hypoxic-ischaemic encephalopathy complications. Comparison of umbilical artery pH, PO(2), PCO(2), base deficit was done between the two groups with Student's t tests. MAIN OUTCOME MEASURES: Umbilical artery pH, PO(2), PCO(2) and base deficit. RESULTS: The PO(2) was significantly higher in the group that expired (18.36 +/- 9.15 vs 12.33 +/- 7.51). There were no significant differences in any other blood gas parameters between the groups. CONCLUSION: Neither the umbilical artery pH nor base deficit is predictive of neonatal death in infants with hypoxic-ischaemic encephalopathy with seizures. The finding of a high PO(2) in neonates who died may indicate an inability of those infants to efficiently extract oxygen from blood.     

An assessment of the use of meconium alone as an indication for fetal blood sampling.

OBJECTIVE: To assess the validity of meconium as an indication for fetal blood sampling. METHODS: The study design was a prospective observational study in a teaching hospital. Fetal blood samples were taken from 401 women. One hundred sixty-five patients had meconium-stained amniotic fluid (77 of whom had no cardiotocographic abnormalities). In the remaining 236 patients, the indication for fetal blood sampling was cardiotocographic abnormalities without meconium. The main outcome measures were the values of pH and base excess obtained at fetal blood sampling, 1-minute Apgar scores, and umbilical artery pH values. RESULTS: Patients with meconium alone as an indication for fetal blood sampling had higher scalp sample pH values (P < .001) and 1-minute Apgar scores (P < .01) than laboring patients with both meconium and cardiotocographic abnormalities. The patients with meconium alone had higher scalp pH values than patients with cardiotocographic abnormalities but no meconium (P < .001). In only two patients with meconium alone was a fetal scalp pH less than 7.20 (both infants had good Apgar scores at delivery). However, when cardiotocographic abnormalities were present, the finding of meconium was significant, resulting in lower 1-minute Apgar scores (P < .01) despite a lack of difference in fetal blood sample pH values. CONCLUSION: In the absence of cardiotocographic abnormalities, meconium is not an indication for fetal blood sampling.     

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.     

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.