Original Article

The impact of introducing universal umbilical cord blood gas analysisand lactate measurement at delivery

Christopher R.H. WHITE,1 Dorota A. DOHERTY,1,2 John P. NEWNHAM1,2 andCraig E. PENNELL1,2

1School of Women’s and Infants’ Health, The University of Western Australia, and 2Women and Infants Research Foundation, Perth,Western Australia, Australia

Background: There is growing support for umbilical cord blood gas analysis (UCBGA) to be conducted at delivery. Arecent study in a tertiary level obstetric unit found that universal UCBGA was associated with improved perinataloutcomes, but there is less evidence of benefit in lower-risk environments. In such settings, lactate analysis may be asuitable alternative.Aims: This study evaluated the introduction of universal UCBGA into a secondary obstetric unit and universal umbilicalcord lactate analysis program into primary and secondary units.Methods: After education, universal UCBGA or lactate analysis was introduced into one primary and two secondary levelobstetric units. Univariate and adjusted analysis assessed changes in UCBGA values and Apgar scores over the studyperiod.Results: There were no significant changes in mean blood gas and lactate values at any centre following introduction ofuniversal UCBGA or lactate analysis. However, there was at the primary level obstetric unit a significant reduction in theproportion of neonates with moderate to severe elevations in umbilical artery lactate values. There was a non-significantreduction in arterial pH values less than 7.10 at the secondary metropolitan centre.Conclusion: The data presented in this study suggest that the benefits of introducing UCBGA into a tertiary obstetriccentre may be reproduced in a primary obstetric centre within 12 months of implementation. Larger studies are requiredin secondary units to assess infrequent adverse obstetric and neonatal outcomes.

Key words: acidaemia, blood gas analysis, implementation, perinatal asphyxia, umbilical cord.

Introduction

There is increasing support amongst many academicorganisations and professional colleges for performingumbilical cord blood gas analysis (UCBGA) at delivery.1–5

The information provided by umbilical cord blood gasvalues is integral to the identification and classification ofperinatal hypoxic-ischaemic insults.4,6 Further, there is agrowing body of data demonstrating the medico-legal,financial, neonatal and educational benefits of UCBGAwhen performed on all deliveries.7–10

The introduction of universal UCBGA into a tertiarylevel maternity unit with 19,426 deliveries over a four-yearperiod resulted in a progressive improvement in mean

arterial pH, pO2, pCO2, base excess and lactate values(P < 0.05).7 Moreover, following introduction of universalUCBGA, there was a 16% reduction in the proportion ofneonates with arterial pH values <7.00, 27% reductionin arterial pH <5th centile (7.12), 25% reductionin arterial base excess <5th centile (�9.3 mmol/L) and60% reduction in arterial lactate levels >95th centile(6.7 mmol/L). These significant reductions in theproportions of individuals with metabolic acidosisremained significant after accounting for case complexityand demographic factors. The authors postulated thatthese improvements might be secondary to education andimprovements in clinical practice resulting frombiochemical biofeedback provided by objective markers ofneonatal status.In some perinatal units, cord blood gas analysis may not

be a feasible option, due to the expense of equipment andsmall numbers of deliveries. In these units, umbilical cordblood lactate analysis has been proposed as an alternativethat can be performed for a fraction of the cost.11,12

Significant correlations have been demonstrated betweenumbilical artery lactate values and a range of markers of

Correspondence: Mr Christopher White, School of Women’sand Infants’ Health M550, The University of WesternAustralia, 2nd Floor, A Block, King Edward MemorialHospital, Subiaco, WA 6008, Australia.Email: christopher.white@uwa.edu.au

Received 7 April 2013; accepted 9 August 2013.

© 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists 71

Australian and New Zealand Journal of Obstetrics and Gynaecology 2014; 54: 71–78 DOI: 10.1111/ajo.12132

Th e Australian and New Zealand Journal of Obstetrics and Gynaecology

neonatal status, including Apgar scores, umbilical artery pHvalues and umbilical artery base excess values.13–17 Further,umbilical artery lactate values have been shown to beequivalent to arterial blood gas values in the prediction of avariety of adverse clinical and neonatal outcomes.12,15,18 Arecent large cohort study demonstrated that combining datafrom umbilical artery lactate levels and neonatalresuscitation level produces the most effective predictor ofmoderate-severe hypoxic-ischaemic encephalopathy, with asensitivity of 85% and a specificity of 99%.18

Despite the evidence demonstrating the value ofuniversal UCBGA, the value in non-tertiary obstetric unitsremains uncertain. The aim of this study was to evaluatewhether the improvements in neonatal outcomes seenfollowing introduction of universal UCBGA into a tertiaryobstetric unit could be reproduced in primary andsecondary level perinatal units in metropolitan andregional Western Australia.

Materials and Methods

A prospective observational study was conducted at threeobstetric units in Western Australia: one regional primaryunit, one regional secondary unit and one metropolitansecondary unit. The Women’s and Children’s HealthService Research Ethics Committee and the WesternAustralian Country Health Board Research EthicsCommittee granted approval for the study. All neonatesdelivered from 24 weeks’ gestational age onwards wereincluded, apart from fetal deaths diagnosed prior tolabour. Detailed information on all deliveries was recordedin institutional electronic databases or in written birthregisters at each location. Maternal, obstetric and neonatalcharacteristics available for use in analysis includedmaternal age, parity, mode of delivery, gestational age,labour induction and augmentation, maternal anaesthesiaand analgesia, plurality, gestational age and neonatal birthweight.Paired umbilical arterial and venous blood samples were

collected at all deliveries for blood gas or lactate analysis.Immediately after delivery, with the placenta in-situ andideally prior to the neonate’s first breath, an umbilical cordsegment was isolated utilising cord clamps. Arterial andvenous samples were collected using one-millilitre pre-heparinised plastic syringes and 21-gauge needles.Analysis was performed five to ten minutes after collectionof samples.In the centres undertaking lactate analysis (primary and

regional secondary units), umbilical lactate was measuredusing a Roche AccusportTM hand-held lactate meter(Boehringer Mannheim, Germany). In the centreundertaking full blood gas analyses (metropolitansecondary unit), measurement was performed on pairedarterial and venous samples using a GEM Premier 3000TM

(Abacus ALS, Australia) analyser located in the Labourand Delivery Ward. The blood gas analyser was calibrateddaily by hospital technical staff members while the lactatemeters were calibrated after every 20 samples. The

midwifery staff, usually those who collected the samples,undertook all analyses. All staff members were required tomeet minimum competency standards in sampling andmeasurement techniques.Paired cord blood gas samples were evaluated for

accuracy using the King Edward Memorial Hospital(KEMH) model to exclude results with a high likelihoodof sampling error,19 with all comparisons of blood gas dataperformed on paired samples validated with these criteria.For the centres in which umbilical lactate analysisoccurred, no equivalent algorithm for minimumarteriovenous lactate differences exists. As a consequence,all comparisons of lactate data were performed on thecohort of neonates that had both umbilical arterial andvenous lactate values reported.To identify neonates at greatest risk of morbidity and

mortality arising from metabolic acidosis, establishedpre-defined thresholds of umbilical artery blood gases andlactate values were utilised (pH < 7∙0; pH < 7.1; BE <�12 mmol/L; lactate > 6∙1 mmol/L; lactate > 6∙7 mmol/L).7,20–22

Statistical analysis

Categorical obstetric and neonatal characteristics weresummarised using frequency distributions, whilecontinuous data were summarised with means andstandard deviations (SD). Univariate comparisons over thestudy period were conducted using chi-square tests forcategorical data and analysis of variance for continuousdata. Univariate and multivariable (or adjusted) logisticregression was used to assess the likelihood of cord arterialblood gas and lactate values falling outside pre-definedthresholds presented using odds ratios (OR) and their95% confidence intervals (CI). Maternal, obstetric andneonatal characteristics were considered as candidatepredictors as well as the time point within the study periodin which the neonate was born. Cord blood gas and lactatevalues were compared across the study period usingmultivariable linear regression, with adjusted means andtheir standard error of mean being estimated. The studyperiod was divided into four epochs of six months forunits A and C providing two years of study, and threeepochs of six months for unit B providing 18 months forstudy. This approach to analysis was undertaken tominimise the effect of temporal variations. All hypothesistests were two-sided with P-values less than 0∙05considered statistically significant. SPSS statistical softwarewas utilised for analysis (SPSS Inc., Version 15.0,Chicago, IL).

Results

Lactate measurement on umbilical arterial and venousblood was introduced into two maternity units, a regionalprimary obstetric centre (Unit A) and a regional secondaryobstetric centre (Unit B). Unit A had 1,073 deliveriesbetween December 2009 and February 2011, and Unit B

72 © 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists

C. R. H. White et al.

had 1,891 deliveries over a period spaning between July2009 and September 2011. At the secondary metropolitanobstetric unit (Unit C), universal UCBGA was undertakenon 3,340 deliveries between July 2009 and June 2011.During the study period, there were two fetal deathsidentified prior to labour at Unit A, five at Unit B and 14 atUnit C. Analysis of demographic, intrapartum and obstetricdata revealed no significant change within each maternityunit in these covariates over the study period (Table 1.).

Umbilical cord blood lactate analysis

At the centres where umbilical cord blood lactate analysiswas conducted, the regional primary level one obstetriccentre (Unit A) had at least one lactate value available foranalysis in 62.0% (n = 811) of the population; the regionallevel two obstetric unit (Unit B) had at least one lactatevalue for 83.6% (n = 1394) of the population. Botharterial and venous lactate values were available for 59.7%(n = 782) at Unit A and 78.5% (n = 1310) at Unit B.Over the duration of this study, there was variation in theproportion of neonates with lactate values in none, one ortwo umbilical vessels at both Unit A and Unit B; thevariation was around a point rather than a pattern ofincrease or decrease.At the regional primary obstetric centre (Unit A), there

were no significant changes in the mean arterial lactatevalues over the three time epochs evaluated in univariateand multivariable analyses (Table 2). Significant variationin the mean umbilical venous lactate values occurred overthe time epochs in both univariate and multivariableanalyses (P = 0.006 and P = 0.001, respectively),although there was no pattern of overall increase ordecrease.In the regional primary obstetric unit, there was a

significant reduction in arterial lactates levels greater thanthe 95th percentile over time (>6.1 mmol/L, 16.3–7.8%:OR = 0.394, 95%CI = 0.205–0.759, P = 0.005) and 99thpercentile (>6.7 mmol/L, 8.5–2.8%: OR = 0.304, 95%CI = 0.112–0.823, P = 0.019) (Fig. 1). These changesbecame apparent within the first twelve months of testing(Epoch One vs Epoch Two). These differences persistedafter adjustment for multiple maternal, obstetric andintrapartum covariates (Table 3).For Unit B, the regional level two obstetric centre,

significant variation was noted in the average arterial andvenous lactate values in both univariate and multivariableanalysis (all P < 0.001) (Table 2): the variation wasaround a point rather than a pattern of increase ordecrease. Across the study period, there was significantvariation in the proportion of neonates with an arteriallactate value greater than 6.7 mmol/L; only occurringwhen comparing the first versus the last period.Unadjusted logistic regression analysis noted a significantincrease in the proportion of neonates with arterial lactatevalues greater than 6.1 mmol/L and 6.7 mmol/L whencomparing epoch one with epoch four (Table 3). Afteradjusting for demographic, obstetric and intrapartum

covariates, the changes were no longer statisticallysignificant (Table 3).

Umbilical cord blood gas analysis

At the metropolitan secondary level obstetric unit (UnitC), 84.5% (n =2812) of the neonates had at least onecord blood gas result recorded, with 73.6% (n = 2451)having a set of results for both the umbilical artery andumbilical vein. Over the two years of evaluation, therewas no significant difference in the proportion ofneonates with paired validated umbilical cord blood gasvalues (P = 0.429). Univariate comparison of meanumbilical cord blood gas values revealed significantvariation in arterial pO2 (P = 0.006) values around apoint with no pattern of increase or decrease over thetwo-year study period (Table 2). These changesremained significant after adjusting for maternal, neonataland obstetric covariates. In the metropolitan secondaryobstetric centre, there was a 21% reduction in arterialpH<7.10 over the four epochs (from 7.3%to 5.8%) whichdid not reach statistical significance. Similarly, univariateand multivariable logistic regression revealed nosignificant reduction in the proportion of neonates withmeasures of acidosis outside the predefined thresholdswhen the first time epoch was compared with each of thesubsequent three (Table 3).

One-, five- and ten-minute Apgar scores

Evaluation of the one and five minute Apgar scores atUnit B over the study period revealed no significantvariation in the proportion of neonates with Apgar scoresless than four or less than seven. Unadjusted and adjustedlogistic regression analyses noted no significant differencesbetween the first and any of the following time periods. AtUnit C, there were no significant changes in one-, five- orten-minute Apgar scores over the study period inunivariate and multivariable logistic regression. No Apgarscores were available for analysis at Unit A.

Discussion

This study represents the first evaluation of which we areaware of the impact of introducing cord blood gasanalyses into primary and secondary obstetric units inmetropolitan and regional centres. The data presenteddemonstrate a 61% reduction in arterial lactate levelsgreater than the population based 95th percentile and a69% reduction in arterial lactate levels greater than the99th percentile.The reduction in the rate of metabolic acidaemia in the

primary obstetric centre is of similar magnitude to thatseen when UCBGA was introduced into a tertiaryobstetric centre with more than 6000 deliveries per year.7

In the larger study, there was also a significant reductionin the number of admissions of term babies to the specialcare nursery. The present study did not have adequate

© 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists 73

Universal cord blood gas or lactate analysis

power to assess nursery admission in any of the threecentres evaluated. The similar pattern and magnitude ofchange suggest that it is possible that the mechanismresponsible for this improvement may be similar at bothsites.

The primary mechanism postulated for the reduction inmoderate and severe metabolic acidaemia and nurseryadmission noted in the previous study was biochemicalbiofeedback to the clinical staff.7 It has been postulatedthat the additional biochemical information afforded by

Table 1 Demographic and intrapartum characteristics at cord blood gas analysis sites

Time epoch

P-valueOne Two Three Four

Unit A (Primary Regional Obstetric Unit)Maternal age (years)<20 30 (6.7) 22 (5.1) 30 (7.0) – 0.53620–39 410 (91.3) 395 (91.6) 390 (90.9) –>39 9 (2.0) 14 (3.2) 9 (2.1) –

Nulliparous 173 (38.5) 158 (36.7) 159 (37.1) – 0.833Term gestation 437 (97.3) 418 (97.2) 419 (97.7) – 0.824Birth weight (grams)<2500 14 (3.1) 9 (2.1) 10 (2.3) – 0.8452500–3999 388 (86.4) 379 (87.9) 371 (86.5) –>3999 47 (10.5) 43 (10.0) 48 (11.2) –

Multiple birth 8 (1.8) 6 (1.4) 0 (0.0) – 0.027Induction/augmentation 239 (53.2) 240 (55.7) 242 (56.4) – 0.609Vaginal Delivery 252 (56.1) 238 (55.5) 237 (55.4) – 0.996Instrumental delivery 58 (12.9) 57 (13.3) 54 (12.6) –

Caesarean delivery 139 (31.0) 134 (31.2) 137 (32.0) –Unit B (Secondary Regional Obstetric Unit)Maternal age (years)<20 31 (7.3) 21 (5.0) 28 (7.2) 32 (7.3) 0.71120–39 378 (89.6) 385 (92.5) 35 (89.8) 390 (89.0)>39 13 (3.1) 10 (2.4) 12 (3.1) 16 (3.7)

Nulliparous 157 (37.2) 161 (38.6) 164 (41.9) 176 (40.2) 0.546Term gestation 407 (96.4) 393 (94.2) 366 (93.6) 416 (95.0) 0.288Birth weight (grams)<2500 15 (3.6) 17 (4.1) 16 (4.1) 10 (2.3) 0.7332500–3999 352 (83.4) 343 (82.3) 325 (83.1) 376 (85.8)>3999 55 (13.0) 57 (13.7) 50 (12.8) 52 (11.9)

Multiple birth 8 (1.9) 6 (1.4) 10 (2.6) 8 (1.8) 0.710Induction/augmentation 180 (42.7) 170 (40.8) 180 (46.0) 197 (45.0) 0.424Vaginal delivery 222 (52.6) 241 (57.8) 215 (55.0) 233 (53.2) 0.486Instrumental delivery 56 (13.3) 55 (13.2) 42 (10.7) 62 (14.2)Caesarean delivery 1473 (34.0) 121 (29.0) 134 (34.3) 143 (32.6)

Unit C (Secondary Metropolitan Obstetric Unit)Maternal age (years)<20 years 40 (5.0) 26 (3.3) 24 (3.1) 37 (3.9) 0.34920–39 736 (92.8) 745 (93.6) 728 (94.5) 901 (93.8)>39 17 (2.1) 25 (3.1) 18 (2.3) 23 (2.4)

Nulliparous 362 (45.7) 331 (41.7) 363 (47.2) 455 (47.3) 0.080Term gestation 779 (97.1) 773 (96.9) 745 (96.5) 931 (96.7) 0.905Birth weight (grams)<2500 23 (2.9) 10 (1.3) 19 (2.5) 24 (2.5) 0.2092500–3999 680 (85.9) 692 (86.9) 679 (88.2) 825 (85.8)>3999 89 (11.2) 94 (11.8) 72 (9.4) 112 (11.7)

Multiple birth 8 (1.0) 12 (1.5) 4 (0.5) 12 (1.2) 0.270Induction/augmentation 393 (49.0) 414 (51.9) 391 (50.6) 483 (50.2) 0.713Vaginal delivery 442 (55.9) 457 (57.6) 446 (57.9) 560 (58.3) 0.632Instrumental delivery 123 (15.5) 103 (13.0) 101 (13.1) 142 (14.8)Caesarean delivery 226 (28.6) 234 (29.5) 223 (29.0) 259 (27.0)

74 © 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists

C. R. H. White et al.

UCBGA provides an objective feedback mechanism inrelation to intrapartum management practices. This inturn can reinforce behaviour associated with favourablefetal outcomes while potentially identifying and modifyingsuboptimal behaviour associated with adverse outcomesand nursery admissions. Consequently, UCBGA appearsto have advantages outside the diagnostic and medico-legalfield, and the use of universal cord blood gas analysiscould be considered for all maternity units. Thishypothesis was supported by the observation that, as timeprogressed after the introduction of universal cord bloodgas analyses, the use of tools to assess fetal condition(such as fetal scalp stimulation and scalp pH sampling)occurred in more timely manner. This subsequentlyresulted in the delivery of babies in better conditionwithout an increase in the rate of instrumental deliveries orcaesarean section. Further studies are required to morecarefully evaluate the potential mechanisms for theimprovements seen by White et al.7 and in this study.Taking the findings of this study together with the

previous evaluation of the introduction of universalUCBGA into a tertiary level maternity unit now providesa reasonable body of evidence to support the introductionof universal UCBGA into all maternity units. For this tooccur, universal UCBGA would need to be simple, quick,supported by the clinical staff and have demonstratedcost-benefit.Collecting blood for UCBGA is technically simple, takes

several minutes to perform and can be easily taught tostaff. In this study, the education package required forimplementation, ongoing education and quality assurancerequired one senior registered midwife employed for eighthours a week. The timelines for processing of umbilicalcord blood gas samples are relatively robust and shouldnot interfere with clinical care. A recent randomisedcontrolled trial demonstrated that cord blood gas valuescan remain stable for up to 60 minutes even if thesegment of cord is clamped at both ends and left on thedelivery tray by the bedside.23 Cord lactate samplesrequire analyses within 15 minutes to prevent statisticallysignificant changes in values; however, this is easilyachievable with the availability of inexpensive point of caremeters that can be kept at the bedside.23 While lactatevalues are more likely to be influenced by delays inanalysis, they are associated with a considerably smallerinitial cost outlay than UCBGA,11 suggesting that lactateanalysis may be a valid and cheaper alternative toUCBGA in primary level units where access to a bloodgas analyser is not easily achievable.A proportion of neonates at the sites conducting

universal umbilical lactate analysis did not have umbilicallactate values reported, in part due to analyser associatedtechnical difficulties. The lactate meters that are currentlycommercially available were developed primarily for use insports medicine and are typically based on glucometers.Consequently, the analysers are designed for bloodsamples obtained from finger pricks, which whilstadvantageous in terms of the small blood volume required,T

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© 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists 75

Universal cord blood gas or lactate analysis

means that the comparatively large volumes of bloodavailable from umbilical cord blood sampling can bedisadvantageous. Application of large volumes of blood tothe lactate meter can result in blood entering the meterand damaging the meter. To ameliorate this, educationprograms were instituted at each of the study sites toinform the staff members of appropriate sample volume,analysis method and cleaning protocols.

When this study was performed, an evaluation of staffattitudes and barriers to the introduction of umbilical cordblood gas and lactate analysis at birth was performedsimultaneously.24 This study demonstrated that, despitepopular belief, most respondents considered UCBGAbeneficial to perinatal care, with only 8% of staff believingUCBGA had no place in perinatal care. The informationderived from this study may be useful in identifying and

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76 © 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists

C. R. H. White et al.

resolving concerns prior to the introduction of UCBGA.Further, it could be useful in the preparation of educationand implementation packages necessary for introduction ofUCBGA.The present study has a number of limitations,

including its limited sample size and the short duration ofevaluation after implementation of universal UCBGA.Larger sample sizes would enable assessment ofinfrequent adverse obstetric and neonatal outcomes, suchas hypoxic-ischaemic encephalopathy and perinatalmortality secondary to hypoxic-ischaemic injury, as wellas cost-benefit in terms of reducing the number ofneonatal transfers to tertiary units. Only one study todate, to our knowledge, has followed obstetric andneonatal outcomes for a prolonged period of time afterimplementation of universal UCBGA.7 That studymonitored outcomes for 4 years after implementation anddemonstrated sustained neonatal benefits. Longer follow-up studies in primary and secondary obstetric centres willbe required to evaluate whether the benefits of UCBGAare sustained.

Conclusion

Evaluation of the effects of introducing umbilical lactateand blood gas measurements at birth into primary andsecondary level obstetric units has shown benefits similarto those previously observed when introduced for all birthsin a tertiary level environment.

Ethics Approval

This study received ethics approval from the Women’sand Children’s Health Service Ethics Committee(Reference Number EC07-12) on the 4th of September2007 and the West Australian Country Health ServiceEthics Committee (Reference Number 2009:03) on the23rd of March 2009.

Acknowledgements

We thank the medical and midwifery staff members at allof the participating hospitals.

References1 ACOG. ACOG Technical Bulletin No. 216: umbilical artery

blood acid-base analysis. Int J Gynaecol Obstet 1996; 52 (3):305–310.

2 ACOG. ACOG Committee Opinion No. 348: umbilical cordblood gas and acid-base analysis. Obstet Gynecol 2006; 108(5): 1319–1322.

3 RCOG, RCM. Towards safer childbirth. Minimum standardsfor the organisation of labour wards. Report of a joint workingparty. London: 1999.

4 MacLennan A. A template for defining a causal relationbetween acute intrapartum events and cerebral palsy: inter-national consensus statement. BMJ 1999; 319 (7216): 1054–1059.T

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5)0.88

7(0.540

,1.45

8)0.73

9(0.455

,1.20

1)BE

<�1

2mmol/L

1.15

1(0.441

,3.00

7)0.82

0(0.283

,2.38

2)0.75

3(0.271

,2.09

0)0.98

5(0.368

,2.63

6)0.72

8(0.245

,2.16

3)0.67

0(0.236

,1.89

8)

†Significant

differen

cebetw

eenep

ochs

(P-value

<0.05

)arein

bold.

© 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists 77

Universal cord blood gas or lactate analysis

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78 © 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists

C. R. H. White et al.