Umbilical artery pH and base excess at birth are poor predictors of neurodevelopmental morbidity in early childhood.

In Brief Objective To measure umbilical cord blood oxygen saturation, to calculate preductal oxygen saturation at birth, and to assess its predictive value for acidosis. Methods Umbilical cord blood samples of 1537 live-born singleton neonates were analyzed. Oxygen saturation was measured by spectrophotometry; pH and base excess were measured by a pH and blood gas analyzer. Preductal oxygen saturation was calculated with an empirical equation. Acidosis was defined as 2 standard deviations (SDs) below the mean of umbilical artery (UA) pH or base excess (7.09 and −10.50 mmol/L, respectively). The predictive value for acidosis of UA and umbilical vein (UV) oxygen saturation and calculated preductal oxygen saturation was determined with receiver operating characteristic curves. Results The mean values (±SD) of UV, UA, and calculated preductal oxygen saturation were 52 ± 18%, 26 ± 17%, and 31 ± 16%, respectively. Forty-seven neonates had UA pH less than 7.09 and 60 had UA base excess less than −10.50 mmol/L. The UV, UA, and calculated preductal oxygen saturation showed considerably weaker relations to UA base excess (multiple r2 = .056, .003, and .017, respectively; P < .001) than to UA pH (multiple r2 = .112, .126, and .148, respectively; P < .001). Receiver operating characteristic areas under the curve were higher when predicting low pH compared with low base excess (for UV, UA, and calculated preductal oxygen saturation: 0.716 versus 0.699, 0.747 versus 0.586, and 0.765 versus 0.628, respectively). The difference was significant for UA oxygen saturation (P < .05). All tests showed high sensitivity and negative predictive values, but low specificity and positive predictive values. Conclusion Low fetal oxygen saturation measured at birth seemed to be associated with low fetal pH and base excess values, but its predictive value for acidosis in an unselected population was limited, particularly if acidosis was metabolic. Low fetal oxygen saturation measured at birth seems associated with low fetal pH and base excess values, but its predictive value for acidosis is limited, particularly if acidosis is metabolic.

Low fetal oxygen saturation at birth and acidosis

This systematic review and meta-analysis aimed to compare the effects of using phenylephrine or norepinephrine on the pH and base excess (BE) of the umbilical artery and vein in parturients undergoing cesarean section. The study protocol was registered in INPLASY. Independent researchers searched Ovid-Medline, Ovid-EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) databases and Google Scholar for relevant randomized controlled trials (RCTs). The primary outcome of this study was the umbilical artery (UA) or umbilical vein (UV) pH as neonatal condition at birth, and the secondary outcome was the UA or UV BE as an additional prognostic value over the measurement of umbilical pH. There was no evidence of a difference between phenylephrine and norepinephrine for overall, UA, and UV pH (mean difference (MD) -0.001, 95% confidence interval (CI) -0.004 to 0.007; MD 0.000, 95%CI -0.004 to 0.004; and MD 0.002, 95%CI -0.013 to 0.017). There was also no evidence of a difference between phenylephrine and norepinephrine for overall, UA, and UV BE (MD 0.096, 95% CI -0.258 to 0.451; MD 0.076, 95%CI -0.141 to 0.294; and MD 0.121, 95%CI; -0.569 to 0.811). A meta-regression showed that factors such as umbilical artery or vein, infusion method, single or twin, and the number of parturients per study had no effect on the UA pH, UV pH, UA BE, or UV BE. No evidence of publication bias was detected. There was no evidence of a difference between phenylephrine and norepinephrine for umbilical pH and BE. A subgroup analysis and meta-regression also did not show evidence of differences.

Neonatal acid-base status before and after discontinuing routine left uterine displacement for elective cesarean delivery: a retrospective cohort study (2014-2017).

336: Effects of intrapartum fever on umbilical artery pH, lactate and base excess

To determine if an amniotic fluid index (AFI) < or =5.0 cm within 7 days of delivery in the third trimester is associated with decreasing umbilical arterial pH and base excess. Cases for this retrospective cohort study were all pregnancies > or =26 weeks with intact membranes and an AFI < or =5.0 cm within 7 days of delivery between 11/99 and 7/02. Multiple gestations, aneuploid, and anomalous fetuses were excluded. Controls with an AFI >5.0 cm within 7 days of delivery were matched to each case within 1 week by gestational age. For a control group with a mean+/-SD umbilical arterial pH of 7.26+/-0.07 and alpha=0.05, a sample size of 100 would have a power of 99% to detect a difference with a study group whose mean was 7.20. Data were compared using paired Student's t-test, Mann-Whitney, Fisher's exact, chi(2) and risk ratios with 95% confidence intervals. In all, 131 neonates with an AFI < or =5.0 cm were matched to 131 controls with an AFI >5 cm. There was no difference in gestational age (37.6+/-3.0, 37.7+/-3.0 weeks) or birth weight (2897+/-810, 2762+/-788 g). There was no difference in umbilical artery pH (7.25+/-0.07, 7.26+/-0.07) or base excess (-3.32+/-2.59, -2.83+/-2.45 mmol/l), even in small for gestational age (SGA) infants in both groups. There was no difference in the number of SGA neonates, 5-minute Apgar <7, respiratory distress syndrome, necrotizing enterocolitis, or neurologic morbidity. Linear regression showed no correlation between AFI and either umbilical arterial pH (r=-0.00047, SE=0.001, p=0.63) or base excess (r=-0.029, SE=0.037, p=0.428). An AFI < or =5.0 cm measured within 7 days of delivery in the third trimester is not associated with decreasing umbilical arterial pH and base excess.

There has been some controversy regarding the effect that a long labor can have on fetal well-being. This study was undertaken to evaluate the effect of duration of labor both the first and second stage on the acid-base variables in the umbilical artery of the newborn. Bloodsampling was attempted from all infants born at our department between October 1994 and September 1995. Nineteen hundred and forty-one live infants were delivered during the period. Sampling was unsuccessful in 264 cases and after excluding infants with operative delivery, multiple gestations, breech presentation, prematurity, postmaturity and infants small for gestational age 1255 remained singleton, term infants with vertex presentation and non-operative vaginal birth. We found no correlation between duration of the first stage of labor and neither pH nor base excess in umbilical artery blood. There was a significant correlation between duration of the second stage of labor and both the pH and base excess. For vaginal nulliparas we found that pH=7.30-0.016 x second stage duration in hours and base excess=-3.71-0.692 x second stage duration in hours. For women with previous vaginal births pH=7.31-0.029 x second stage duration in hours and base excess=-2.38-1.306 x second stage duration in hours. We find no correlation between duration of the first stage of labor and umbilical artery pH or base excess. We do find a correlation between duration of the second stage of labor and the umbilical artery pH and base excess. However, a prolongation of the second stage with as much as three hours would give an expected lowering of the umbilical artery pH with only 0.05 and of base excess with 2.1 mmol/l for vaginal nulliparas and correspondingly with 0.09 and 3.9 mmol/l in women with previous vaginal births. This effect on pH and base excess is so small that it is hardly clinically relevant and we do not find any support for the belief that a long labor -- in the absence of other risk factors -- is to the disadvantage of the fetus.

A simple software routine for the reproducible processing of the electrocardiogram

The fetal electrocardiogram: Relationship with acidemia at delivery

Spinal anesthesia for cesarean delivery is associated with a high incidence of hypotension. Phenylephrine results in higher umbilical artery pH than ephedrine when used to prevent or treat hypotension in healthy women. We hypothesized that phenylephrine compared to ephedrine would result in higher umbilical artery pH in women with preeclampsia undergoing cesarean delivery with spinal anesthesia. This study was a randomized double-blind clinical trial. Nonlaboring women with preeclampsia scheduled for cesarean delivery with spinal anesthesia at Prentice Women's Hospital of Northwestern Medicine were randomized to receive prophylactic infusions of phenylephrine or ephedrine titrated to maintain systolic blood pressure >80% of baseline. Spinal anesthesia consisted of hyperbaric 0.75% bupivacaine 12 mg, fentanyl 15 µg, and morphine 150 µg. The primary outcome was umbilical arterial blood pH and the secondary outcome was umbilical artery base excess. One hundred ten women were enrolled in the study and 54 per group were included in the analysis. There were 74 and 72 infants delivered in the ephedrine and phenylephrine groups, respectively. The phenylephrine:ephedrine ratio for umbilical artery pH was 1.002 (95% confidence interval [CI], 0.997-1.007). Mean [standard deviation] umbilical artery pH was not different between the ephedrine 7.20 [0.10] and phenylephrine 7.22 [0.07] groups (mean difference -0.02, 95% CI of the difference -0.06 to 0.07; P = .38). Median (first, third quartiles) umbilical artery base excess was -3.4 mEq/L (-5.7 to -2.0 mEq/L) in the ephedrine group and -2.8 mEq/L (-4.6 to -2.2mEq/L) in the phenylephrine group (difference -0.6 mEq/L, 95% CI of the difference -1.6 to 0.3 mEq/L; P = .10). When adjusted for gestational age and infant gender, umbilical artery pH did not differ between groups. There were also no differences in the umbilical artery pH stratified by magnesium therapy or by the severity of preeclampsia. We were unable to demonstrate a beneficial effect of phenylephrine on umbilical artery pH compared with ephedrine. Our findings suggest that phenylephrine may not have a clinically important advantage compared with ephedrine with regard to improved neonatal acid-base status when used to prevent spinal anesthesia-induced hypotension in women with preeclampsia undergoing cesarean delivery.

Background: Neonatal umbilical artery blood-gas analysis is a diagnostic procedure performed shortly after birth to assess the acid-base balance, oxygenation, and metabolic status of a newborn infant. This retrospective study aimed to investigate the association of prenatal maternal fever with neonatal umbilical artery blood-gas analysis. Methods: A retrospective analysis was conducted on data from 333 parturients and their newborns. Demographic characteristics, clinical information, and neonatal umbilical artery blood gas analysis data were analyzed to evaluate the association between prenatal maternal fever and neonatal blood-gas analysis. Pregnant women with fever (≥38.0 °C) during labor were compared with those without fever. Neonatal umbilical artery blood gas parameters were assessed in relation to the degree and duration of maternal fever. Results: The incidence of the adverse delivery outcome of parturients with high prenatal fever and long duration of fever was significantly higher than that of the low fever, short-term fever, and normal parturients (p &lt; 0.05). The pH of neonatal umbilical veins in the high fever groups was reduced compared with the control group (p &lt; 0.05). Lactic acid (Lac) of neonatal umbilical vein in the low fever and high fever groups was enhanced compared with the control group (p &lt; 0.05). The pH of neonatal umbilical veins in the short-term fever and long-term fever groups was elevated compared with the control group (p &lt; 0.05). The umbilical artery pH and base excess (BE) were positively correlated with maternal peak fever temperature (r = 0.20, r = 0.22, p &lt; 0.05). The umbilical Lac was negatively correlated with maternal peak fever temperature (r = –0.22, p &lt; 0.05). Moreover, the umbilical artery pH and BE were positively correlated with maternal duration of fever (r = 0.29, r = 0.21, p &lt; 0.05). The umbilical artery Lac was negatively correlated with maternal duration of fever (r = –0.25, p &lt; 0.05). Conclusions: The findings suggested that maternal fever during labor was associated with alterations in neonatal umbilical artery blood gas analysis. Understanding the influence of prenatal fever on delivery outcomes is crucial for optimizing maternal and neonatal health.

To evaluate the relationship between umbilical artery cord gas values and fetal tolerance of labor, as reflected by Apgar score. We hypothesized the existence of wide biological variability in fetal tolerance of metabolic acidemia, which, if present, would weaken one fundamental assumption underlying the use of electronic fetal heart rate (FHR) monitoring. We conducted a retrospective cohort study of term, singleton, nonanomalous fetuses delivered in our institution between March 2012 and July 2020. Universally obtained umbilical cord gas values and Apgar scores were extracted. We calculated Spearman correlation coefficients and receiver operating characteristic curves for various levels of umbilical artery pH, base excess, and Apgar scores. We analyzed data from 29,787 deliveries. The statistical correlation between umbilical artery pH and base excess and both 1- and 5-minute Apgar scores was weak or nonexistent in all pH range subgroups (range 0.064-0.213). Receiver operating characteristic curve analysis suggested umbilical artery pH value of 7.22 yields the best discrimination for prediction of a severely depressed newborn (5-minute Apgar score less than 4), but sensitivity and specificity for this predictive value remains poor to moderate. The use of electronic FHR monitoring is predicated on a documented relationship between FHR patterns and umbilical artery pH, and an assumed correlation between pH and fetal outcomes, reflecting fetal tolerance of labor and delivery. Our data demonstrate a weak-to-absent correlation between metabolic acidemia and even short-term fetal condition, thus significantly weakening this latter assumption. No amount of future modification of FHR pattern interpretation to better predict newborn pH is likely to lead to improved newborn outcomes, given this weakness in a fundamental assumption on which FHR monitoring is based.

The so-called 30-minute rule is that hospitals having obstetric facilities should be equipped to perform an emergency cesarean delivery starting within 30 minutes of the decision to operate. This study examined the relationship between the results of umbilical arterial blood gas analysis and the decision-to-delivery interval in emergency cases with nonreassuring fetal status. Improved outcomes with an interval less than 30 minutes would presumably validate the rule. A retrospective cohort study included all cesarean deliveries done for this reason during a 16-month period in the years 2001 to 2003. Three specialists in maternal-fetal medicine, masked to the outcome, received a synopsis of clinical information that would have been available at the time of delivery as well as the last hour of the electronic fetal heart rate tracing. Emergent deliveries were done as soon as possible and deliveries within 30 minutes of the decision to operate. The series included 117 women, 34 classified as emergent and 83 as urgent. General anesthesia was given significantly more often in emergent cases and epidural anesthesia in urgent cases. The decision-to-delivery time was nearly 14 minutes less in the emergent group. There were no differences in 1- or 5-minute Apgar scores, but both the umbilical arterial pH and base excess were significantly worse in emergent cases. The decision-to-delivery interval was nearly 15 minutes shorter for general than for spinal anesthesia and 13 minutes less than with epidural anesthesia. Apgar scores recorded at 5 minutes (but not at 1 minute) were significantly increased with general anesthesia. Umbilical artery pH values did not differ significantly between groups, but base excess was significantly less favorable with general anesthesia. An increased decision-to-delivery interval correlated with improved umbilical arterial pH and base excess. This correlation did not help to predict when the fetus would develop metabolic acidosis severe enough to increase the risk of long-term neurologic morbidity. A very large majority of fetuses had normal values even after 30 minutes. Seven premature infants had intraventricular hemorrhage; 6 of them survived. Only fair to moderate agreement was found between the 3 specialists. Metabolic acidosis is not sensitively predicted by electronic fetal monitoring. In this study, blood gas values remained normal even when birth took place more than 30 minutes after the decision to operate. In the presence of nonreassuring fetal monitoring, the 30-minute rule is a compromise that does not precisely predict how much time will pass before severe metabolic acidosis develops.

IntroductionUmbilical arterial pH of less than 7 is often used as the threshold below which the risks of neonatal death and adverse long‐term neurological outcomes are considered to be higher. Yet within the group with pH <7, the risks have not been further stratified. Here, we aimed to investigate the predictors of adverse long‐term outcomes of this group of infants.Material and methodsThis was a retrospective study of 248 infants born after 34 weeks of gestation in a tertiary obstetric unit, between 2003 and 2017, with cord arterial pH <7 or base excess ≤−12 mmol/L at birth. The infants were categorized into two groups: (1) intact survivors, or (2) neonatal/infant deaths or cerebral palsy or developmental delay. The umbilical arterial pH and base excess levels, Apgar scores, mode of delivery, gestational age, small for gestational age, birth in the era before the implementation of neonatal hypothermic therapy, and the presence of a known sentinel event, were compared between the groups using univariate analysis followed by multivariate analysis.ResultsAmong the 248 infants, there were 222 intact survivors (89.5%) and 26 infants with poor outcomes (10.5%), including eight deaths (3.2%) and 18 (7.3%) with cerebral palsy and/or developmental delay. Univariate analysis showed that infants with adverse outcomes had significantly lower cord arterial pH (6.85 vs 6.95, with p < 0.001), lower cord arterial base excess (−19.95 vs −15.90 mmol/L, p < 0.001), a higher proportion of having AS at 5 min <7 (65.4% vs 13.1%, p < 0.001), and a higher proportion of having a sentinel event (34.6% vs 16.7%, p = 0.034). Multivariate analysis confirmed cord arterial pH of <6.9 and an Apgar score at 5 min <7 as independent prognostic factors (the adjusted odds ratios were 4.64 and 6.62, respectively). The risk of adverse outcome increased from 4.3% when the arterial pH was between 6.9 and <7, to 30% when the pH was <6.9.ConclusionsInfants born with umbilical artery pH <7 still have a high chance of 89.5% to become intact survivors. A cord arterial pH of <6.9 and an Apgar score at 5 min <7 are independent prognostic factors for neonatal/infant death or adverse long‐term neurological outcomes.

Primary aim of the study was to identify risk factors for an adverse neonatal outcome in emergency caesarean deliveries (ECD). Secondary, the influence of the decision-to-delivery interval (DDI) on neonatal outcome was evaluated. Study period of this retrospective investigation was 2001-2011, in which 336 ECD were evaluated. Main outcome measures were risk factors associated with an adverse neonatal outcome (umbilical cord arterial pH <7.05, umbilical cord arterial base excess (BE) <-12, Apgar score at 5min <5 and the combination of umbilical cord arterial pH <7.0, and umbilical cord arterial BE <-12). Secondary, the influence of the DDI on neonatal outcome was assessed. These parameters were tested in univariate and multivariate analyses. Prematurity (<37+0weeks of gestation) and silent cardiotocography (CTG) were identified as the major risk factors for an adverse neonatal outcome. Statistical analyses of the influence of the DDI on umbilical cord arterial pH and BE as well as the Apgar score at 5min revealed no significant results. Our results emphasize the necessity of attendance in a level-3 department of obstetrics in case of conceivable compromised neonatal conditions. Prematurity and silent CTG were identified as the major risk factors for an adverse neonatal outcome. As long as the DDI is under 20min, it did not have an impact on neonatal outcome.