mode of delivery has an independent impact on neonatal condition at birth
TRANSCRIPT
European Journal of Obstetrics & Gynecology and Reproductive Biology 181 (2014) 135–139
Mode of delivery has an independent impact on neonatal condition atbirth
Tomas Prior a,b,c, Sailesh Kumar a,b,c,*a Centre for Fetal Care, Queen Charlotte’s and Chelsea Hospital, Du Cane Road, London W12 0HS, UKb Institute for Reproductive and Developmental Biology, Imperial College London, London W12 0HS, UKc Mater Research Institute/University of Queensland, Aubigny Place, Raymond Terrace, South Brisbane 4101, QLD, Australia
A R T I C L E I N F O
Article history:
Received 29 May 2014
Received in revised form 21 July 2014
Accepted 29 July 2014
Keywords:
Apgar score
Acidosis
Fetal distress
Nonreassuring fetal status
A B S T R A C T
Objective: Current intra-partum monitoring techniques are often criticized for their poor specificity, with
their performance frequently evaluated using measures of the neonatal condition at birth as a surrogate
marker for intra-partum fetal compromise. However, these measures may potentially be influenced by a
multitude of other factors, including the mode of delivery itself. This study aimed to investigate the
impact of mode of delivery on neonatal condition at birth.
Study design: This prospective observational study, undertaken at a tertiary referral maternity unit in
London, UK, included 604 ‘low risk’ women recruited prior to delivery. Commonly assessed neonatal
outcome variables (Apgar score at 1 and 5 min, umbilical artery pH and base excess, neonatal unit
admission, and a composite neonatal outcome score) were used to compare the condition at birth
between babies born by different modes of delivery, using one-way ANOVA and chi-squared testing.
Results: Infants born by instrumental delivery for presumed fetal compromise had the poorest condition
at birth (mean composite score = 1.20), whereas those born by Cesarean section for presumed fetal
compromise had a better condition at birth (mean composite score = 0.64) (p = <0.001). No difference in
composite neonatal outcome scores was observed between babies born by instrumental delivery for a
prolonged second stage (no evidence of compromise), and those born by Cesarean delivery for presumed
fetal compromise.
Conclusions: Mode of delivery represents a potential confounding factor when using condition at birth as
a surrogate marker of intra-partum fetal compromise. When evaluating the efficacy of intra-partum
monitoring techniques, the isolated use of Apgar scores, umbilical artery acidosis and neonatal unit
admission should be discouraged.
� 2014 Published by Elsevier Ireland Ltd.
Contents lists available at ScienceDirect
European Journal of Obstetrics & Gynecology andReproductive Biology
jou r nal h o mep ag e: w ww .e lsev ier . co m / loc ate /e jo g rb
Introduction
Intra-partum fetal hypoxia, resulting in permanent neurologi-cal impairment remains a significant source of concern for parentsand healthcare professionals. Despite improvements in antenataland intra-partum care, the incidence of cerebral palsy in terminfants has not changed in the last 30 years [1]. Whilst in themajority of cases cerebral palsy results from antenatal insults [2], asignificant percentage, particularly in term infants, is caused byintra-partum events [3,4]. Several techniques have been developedwith the aim of identifying the compromised fetus before
* Corresponding author at: Mater Research Institute/University of Queensland,
Level 3, Aubigny Place, Raymond Terrace, South Brisbane 4101, QLD, Australia.
Tel.: +61 7 31632564.
E-mail address: [email protected] (S. Kumar).
http://dx.doi.org/10.1016/j.ejogrb.2014.07.041
0301-2115/� 2014 Published by Elsevier Ireland Ltd.
permanent neurological damage ensues, thereby enabling expe-dited delivery and hopefully improving outcomes for the baby. Themost widely used of these, the cardiotocograph (CTG), has beenreported to have a high false positive rate [5], and as a result CTGmonitoring does not always correlate with the neonatal conditionat birth. Other parameters, including the Apgar score, umbilicalartery pH and base deficit at delivery, and the requirement forneonatal unit admission, are also used to evaluate the newborn atthe time of delivery and are valuable in determining therequirement for further treatment or observation. However,studies evaluating intra-partum monitoring techniques frequentlyuse these measures as an indication of intra-partum fetalcompromise [6,7]. This is perhaps inappropriate given that allthese methods of assessment have the potential to be misleading.Whilst they may suggest intra-partum hypoxia, they are alsoinfluenced by a multitude of other factors. For example, Apgarscores at delivery can be significantly influenced not only by the
T. Prior, S. Kumar / European Journal of Obstetrics & Gynecology and Reproductive Biology 181 (2014) 135–139136
presence of birth asphyxia, but also by prematurity and intra-partum narcotics used for analgesia [8]. Similarly, neonatalacidosis used in isolation is a poor predictor of birth asphyxia.Even a pH <7.00 is associated with a normal post-natal course inthe majority of neonates [8]. Neonatal unit admission, as a singlecriterion, is also misleading, as the indication for admission, suchas sepsis or hypoglycaemia, may be independent of adequate fetaloxygenation during labor [9]. Furthermore, there is potential forthe mode of delivery itself, as well the overall fetal conditionthroughout labor, to influence the condition of the neonate at birth.Respiratory complications, for example, are associated withelective Cesarean delivery [10], and many practicing Obstetricianswill have experienced difficult instru
mental deliveries resulting in a neonate in poor conditiondespite an absence of evidence of fetal compromise throughoutlabor. We have suggested recently that neonates delivered byemergency Cesarean delivery for presumed fetal compromise maybenefit from a period of in-utero resuscitation prior to delivery,resulting in a better than anticipated condition at birth [11].
In this study, we used commonly assessed neonatal outcomevariables to compare condition at birth between neonates born bydifferent modes of delivery. We aimed to determine whether themode of delivery itself may significantly influence the condition atbirth, and as such represent a confounding factor when using theseparameters to determine the presence or absence of intra-partumfetal compromise. We hypothesized that an adverse condition atbirth would occur more frequently amongst babies delivered byinstrumental delivery for presumed fetal compromise, than thosedelivered by emergency Cesarean delivery for presumed fetalcompromise. Even amongst babies with no evidence of fetalcompromise during labor, we hypothesized that condition at birthwould show significant variation between those born by differentmodes of delivery.
Materials and methods
Six hundred and four women were recruited to this prospectiveobservational study over a two-year period, between March 2011and March 2013. All participants were recruited from the deliverysuite, antenatal ward, and day assessment unit at QueenCharlotte’s and Chelsea Hospital. This is a tertiary referralmaternity unit in London, UK. All participants had uncomplicated,term (37–42 weeks), singleton pregnancies. Exclusion criteriaincluded, multiple pregnancy, prematurity, known fetal anomaly,evidence of intrauterine infection, or evidence of placentaldysfunction, including fetal growth restriction, maternal hyper-tension or pre-eclampsia. All labors were managed according tolocal protocols and guidelines, with staff unaware of a participant’sinclusion in the research study in order to limit bias. Intra-partumfetal heart rate patterns were reviewed by an Obstetrician blindedto the intra-partum/neonatal outcomes, and classified according toNICE (National Institute for Health and Care Excellence, UK)criteria as normal, suspicious, or pathological [12]. Mode ofdelivery was classified as Cesarean section for presumed fetalcompromise, Cesarean section ‘other’, instrumental for presumedfetal compromise, instrumental for a prolonged second stage, andspontaneous vaginal delivery (SVD). In all cases, the indication forassisted/surgical delivery was decided contemporaneously by theobstetric team managing the labor. Following delivery, case notes
Table 1Mode of delivery.
Cesarean—fetal
compromise
Instrumental—fetal
compromise
SVD
69 110 238
were examined and neonatal outcomes compared between thedifferent mode of delivery groups. Neonatal outcomes evaluatedincluded the Apgar score at 1 and 5 min, umbilical artery pH,umbilical artery base deficit, neonatal unit admission, andneonatal encephalopathy. For the Apgar score, an adverse outcomewas considered to be a score <7 at 1 or 5 min. This conforms toother studies assessing neonatal outcome, in which a score of <7 isfrequently used to define an adverse outcome [6,13,14]. Forumbilical artery pH, an adverse outcome was defined as a pH<7.20. This level was used as a pH of <7.20 on fetal blood samplingis defined as abnormal in current intra-partum guidelines used inthe UK [12], and is used to prompt immediate delivery. Forumbilical artery base excess, an adverse outcome was considered abase excess of �8.0. This level has been described as a moderatebase deficit in the published literature, and associated with anincreased incidence of central nervous system complications [15].Admission to the neonatal unit was also considered an adverseoutcome. In order to improve the sensitivity of the study fordetecting a difference between mode of delivery groups, thresh-olds defining adverse neonatal outcomes were set deliberately low.A composite neonatal outcome score was also calculatedincorporating all of the neonatal outcomes variables. Points wereawarded dependent on the degree of deviation from normality foreach neonatal outcome variable, and combined to give a compositeoutcome score.
Ethical approval for this study was granted by the LondonResearch Ethics Committee (Ref No: REC 10/H0718/26).
For data analysis cases were grouped according to mode ofdelivery and intra-partum monitoring classification. The neonataloutcome variables were then compared amongst these groupsusing one-way ANOVA and chi-squared tests.
Results
All 604 women recruited to the study gave birth to live infants.The mode of delivery for all cases is documented in Table 1.
Neonatal outcome variables were compared between thedifferent mode of delivery groups (see Table 2). Birthweight,birthweight centile, incidence of Apgar score <7 at 1 min,incidence of umbilical artery pH <7.20, incidence of umbilicalartery base deficit �8.0 mmol/L, and the composite neonataloutcome score, were all found to have significant variationbetween the different mode of delivery groups. For each neonataloutcome variable, the poorest outcomes were observed in infantsdelivered by instrumental delivery for presumed fetal compro-mise. Whilst infants born by emergency Cesarean for presumedfetal compromise had the second highest incidence of an Apgar <7at 1 min, a higher incidence of both umbilical artery pH <7.20 andumbilical artery base deficit �8.0 mmol/L were found in the groupof infants born by SVD. Cases born by instrumental delivery for aprolonged second stage (no evidence of fetal compromise) had anincidence of umbilical artery pH <7.20 at delivery of 25.0% (24/96),and an incidence of an Apgar score <7 at 1 min of 11.5% (11/96).
Cases with normal intra-partum monitoring were then groupedaccording to their mode of delivery (see Table 3). Whilst nosignificant variation in the neonatal outcome variables wasobserved between the mode of delivery groups, a trend towardpoorer outcomes was observed in cases delivered by instrumentaldelivery. These babies had the highest incidence of an Apgar <7 at
Instrumental—prolonged
2nd stage
Cesarean—other
96 91
Table 2Comparison of neonatal outcome variables between mode of delivery groups.
Overall Emergency
Cesarean fetal
compromise
Instrumental
fetal
compromise
SVD Instrumental
prolonged 2nd
stage
Emergency
Cesarean other
ANOVA/
X2 p
Birthweight (g) 3530 (1780–5026) 3426 (2478–4906) 3469 (1780–4940) 3495 (2520–4480) 3618 (2390–5026) 3682 (2690–4506) <0.001
Birthweight centile 53.3 (1–100) 44.39 (1–100) 49.38 (1–100) 52.01 (2–99) 58.27 (2–100) 62.69 (5–99) <0.001
Incidence Apgar
<7 at 1 min
7.5% (45/604) 10.1% (7/69) 14.5% (16/110) 3.8% (9/238) 11.5% (11/96) 2.2% (2/91) 0.001
Incidence Apgar
<7 at 5 min
1.0% (6/604) 1.4% (1/69) 0.9% (1/110) 0.4% (1/238) 2.0% (2/96) 1.1% (1/91) 0.72
Incidence cord
arterial
pH < 7.20
31.3% (189/604) 26.1% (18/69) 47.3% (52/110) 35.3% (84/238) 25.0% (24/96) 12.1% (11/91) <0.001
Incidence base
excess
�8 mmol/L
24.2% (146/604) 11.6% (8/69) 33.6% (37/110) 30.7% (73/238) 22.9% (22/96) 6.6% (6/91) <0.001
Incidence of
neonatal
unit admission
1.5% (9/604) 2.9% (2/69) 2.7% (3/110) 0.8% (2/238) 1.0% (1/96) 1.1% (1/91) 0.57
Incidence of
neonatal
encephalopathy
0% (0/604) 0% (0/69) 0% (0/110) 0% (0/238) 0% (0/96) 0% (0/91) n/a
Composite neonatal
outcome score
0.78 (0–7) 0.64 (0–5) 1.2 (0–5) 0.85 (0–7) 0.70 (0–5) 0.31 (0–5) <0.001
Composite Neonatal outcome scored as follows: (1) Apgar—>7 at 1 min = 0, <7 at 1 min = 1, <7 at 5 min = 2, (2) Cord arterial pH—>7.20 = 0, <7.20 = 1, <7.10 = 2, <7.00 = 3, (3)
Base excess—�8 = 0, �8 and �12 = 1, �12 = 2, (3) NNU admission—No = 0, Yes = 1.
T. Prior, S. Kumar / European Journal of Obstetrics & Gynecology and Reproductive Biology 181 (2014) 135–139 137
1 and 5 min, the highest incidence of umbilical artery pH <7.20 andbase deficit �8.0 mmol/L, and the highest incidence of neonatalunit admission. As a result these babies also had a trend toward thehighest composite neonatal outcome score (i.e. poorest conditionat birth).
The same analysis was performed for cases with suspicious andpathological intra-partum monitoring (see Tables 4 and 5). In bothcases, significant variation was seen in neonatal outcome variablesbetween the different mode of delivery groups. In infants withsuspicious and pathological intra-partum monitoring, the highestcomposite neonatal outcome score was found in infants born bySVD. Composite neonatal outcome scores for both instrumentalgroups (fetal compromise and prolonged 2nd stage) were higherthan both Cesarean groups.
Neonatal outcomes were compared between cases delivered byCesarean or instrumental delivery, in which a diagnosis of fetalcompromise prompted operative delivery. Those born by instru-mental delivery had a significantly higher composite neonataloutcome score (0.64 vs. 1.16, p = 0.006). The same analysis wasperformed for cases with no evidence of intra-partum fetalcompromise, with operative delivery being performed for anindication of a prolonged first or second stage, and on a background
Table 3Comparison of neonatal outcome variables between mode of delivery group in cases w
Overall SVD
Birthweight (g) 3613 (2390–5026) 3537 (2600–
Birthweight centile 59.2 (2–100) 54.8 (2–99
Incidence Apgar <7 at 1 min 2.8% (6/211) 1.4% (3/1
Incidence Apgar <7 at 5 min 0.5% (1/211) 0% (0/115
Incidence Cord
arterial pH < 7.20
20.4% (43/211) 20.9% (24/
Incidence base
excess �8 mmol/L
16.6% (35/211) 17.4% (20/
Incidence of neonatal unit admission 0.9% (2/211) 0.9% (1/1
Incidence of neonatal encephalopathy 0% (0/211) 0% (0/115
Composite neonatal outcome score 0.47 (0–5) 0.47 (0–3
of normal intra-partum monitoring. Again, the highest compositeneonatal outcome score was found in cases delivered by instrumen-tal delivery (0.31 vs. 0.70, p = 0.008). Further comparisons confirmedthat there was no significant difference in the composite neonataloutcome score of infants born by instrumental delivery for aprolonged 2nd stage (0.70) and those delivered by Cesarean forpresumed fetal compromise (0.64) (p = 0.72).
Comment
Results from this study demonstrate that commonly assessedmeasures of neonatal condition at birth including the Apgarscore, umbilical artery pH and umbilical artery base deficit, varysignificantly between infants born by different modes ofdelivery. Whilst the worst outcomes were observed in casesdelivered by instrumental delivery for presumed fetal compro-mise, infants born by emergency Cesarean section for presumedfetal compromise fared better, having better composite neonataloutcome scores than those of any other mode of delivery group,except those cases in which Cesarean delivery was performeddue to failure to progress in labor. These findings are interestingas they raise questions regarding the use of neonatal condition
ith normal intra-partum monitoring.
Instrumental
prolonged 2nd
stage
Emergency
Cesarean other
ANOVA/X2 p
4480) 3688 (2390–5026) 3719 (2690–4506) 0.02
) 62.6 (2–100) 66.2 (5–99) 0.04
15) 4.4% (2/45) 2.0% (1/51) 0.75
) 2.2% (1/45) 0% (0/51) 0.17
115) 26.7% (12/45) 13.7% % (7/51) 0.37
115) 22.2% (10/45) 9.8% (5/51) 0.31
15) 2.2% (1/45) 0% (0/51) 0.51
) 0% (0/45) 0% (0/51) n/a
) 0.62 (0–4) 0.33 (0–5) 0.12
Table 4Comparison of neonatal outcomes between mode of delivery group in cases with suspicious intra-partum monitoring.
Overall Emergency
Cesarean fetal
compromise
Instrumental
fetal compromise
SVD Instrumental
prolonged 2nd
stage
Emergency
Cesarean other
ANOVA/X2 p
Birthweight (g) 3506 (2360–4940) 3389 (2492–4906) 3571 (2360–4940) 3450 (2520–4440) 3553 (2680–4320) 3634 (2878–4470) 0.07
Birthweight centile 51.5 (2–100) 42.8 (2–100) 54.6 (5–100) 49.3 (2–99) 54.3 (5–98) 58.1 (8–99) 0.16
Incidence Apgar
<7 at 1 min
9.9% (27/274) 7.4% (2/27) 21.7% (10/46) 4.3% (5/116) 17.6% (9/51) 2.9% (1/34) 0.005
Incidence Apgar
<7 at 5 min
0.7% (2/274) 0% (0/27) 0% (0/46) 0% (0/116) 2.0% (1/51) 2.9% (1/34) 0.30
Incidence Cord
arterial pH < 7.20
34.3% (94/274) 25.9% (7/27) 34.8% (16/46) 46.6% (54/116) 25.5% (13/51) 11.8% (4/34) 0.02
Incidence base
excess �8 mmol/L
27.0% (74/274) 3.7% (1/27) 23.9% (11/46) 42.2% (49/116) 23.5% (12/51) 2.9% (1/34) <0.001
Incidence of neonatal
unit admission
1.5% (4/274) 0% (0/27) 4.3% (2/46) 0.9% (1/116) 0% (0/51) 2.9% (1/34) 0.35
Incidence of neonatal
encephalopathy
0% (0/274) 0% (0/27) 0% (0/46) 0% (0/116) 0% (0/51) 0% (0/34) n/a
Composite neonatal
outcome score
0.89 (0–7) 0.44 (0–3) 1.02 (0–5) 1.2 (0–7) 0.78 (0–5) 0.32 (0–5) <0.001
T. Prior, S. Kumar / European Journal of Obstetrics & Gynecology and Reproductive Biology 181 (2014) 135–139138
at birth as a surrogate marker for intra-partum fetal compro-mise.
When instrumental and Cesarean deliveries were compared,whether the indication for operative delivery was fetal compro-mise or a failure to progress in labor, condition at birth wassignificantly worse in the instrumental group. Infants born byCesarean delivery for presumed fetal compromise may benefitfrom a period of ‘in utero’ resuscitation prior to delivery [11].Measures such as the cessation of exogenous Oxytocin and a leftlateral position, often undertaken between a decision to deliverand the delivery itself, may influence feto-placental blood flow andresult in an improved condition at birth. In 2006, Bloom et al. foundthat following a decision to deliver by Cesarean section forpresumed fetal compromise, neonatal outcomes were better inbabies with a longer decision to delivery interval [16], proposingthat this was due to reduced clinical urgency in these cases. It isalso possible that these results are explained by the longer periodof in utero resuscitation these babies received. In contrast, babiesdelivered by instrumental delivery for presumed fetal compromiseare likely to have a shorter decision to delivery interval.Furthermore, the increased intra-uterine pressure during thesecond stage of labor will result in a reduction in utero-placentalblood flow [17], potentially influencing the neonatal condition atbirth. In clinical practice, the threshold for a diagnosis of fetalcompromise in labor is likely to be lower in the 2nd stage of labor,
Table 5Comparison of neonatal outcomes between mode of delivery group in cases with path
Overall Emergency
Cesarean fetal
compromise
Instrumental
fetal
compromise
Birthweight (g) 3433 (1780–4858) 3449 (2478–4858) 3383 (1780–4340
Birthweight centile 46.7 (1–100) 45.4 (1–100) 45.1 (1–100)
Incidence Apgar
<7 at 1 min
10.1% (12/119) 11.9% (5/42) 9.5% (6/63)
Incidence Apgar
<7 at 5 min
2.5% (3/119) 2.4% (1/42) 1.6% (1/63)
Incidence Cord arterial
pH < 7.20
43.7% (52/119) 26.2% (11/42) 55.6% (35/63)
Incidence base excess
�8 mmol/L
31.1% (37/119) 16.7% (7/42) 39.7% (25/63)
Incidence of neonatal
unit admission
2.5% (3/119) 4.8% (2/42) 1.6%(1/63)
Incidence of neonatal
encephalopathy
0% (0/119) 0% (0/42) 0% (0/63)
Composite neonatal
outcome score
1.06 (0–5) 0.76 (0–5) 1.25 (0–5)
where a vaginal delivery may be easily achievable, than in the 1ststage of labor, where delivery requires Cesarean section. Despitethis, infants delivered by instrumental delivery had the worstneonatal outcomes, suggesting the mode of delivery itself isinfluential.
There is often significant disparity between the degree ofabnormality used to define compromise at delivery, and that whichis associated with long term impairment. Whilst an Apgar score <7at 5 min is associated with an increased relative risk of subsequentcerebral palsy, epilepsy, and cognitive impairment, the absoluterisk of bad outcomes in these cases is still small [18]. Evidence frommagnetic resonance imaging (MRI) studies suggest moderate orsevere brain lesions are predominantly associated with an Apgarscore of <3 at 1 min, and that even within this group, 28% of caseshad normal imaging or only minor white matter changes [19]. Asdemonstrated in this study, such low Apgar scores occur veryrarely within a normal population (incidence of Apgar <3 at1 min—0.8%, Apgar <7 at 5 min—1.0%), meaning large studypopulations are required to make statistically valid conclusions. Asa consequence, many studies evaluating neonatal outcomes(including this one) have chosen to use the incidence of a lessabnormal Apgar score as a marker of neonatal outcomes (e.g. <7 at1 min). In our study, an Apgar score of <7 at 1 min occurred in11.5% of cases delivered by instrumental delivery for a prolonged2nd stage, cases where there was no intra-partum evidence of fetal
ological intra-partum monitoring.
SVD Instrumental
prolonged 2nd
stage
Emergency
Cesarean other
ANOVA/X2 p
) 3517 (3020–4310) 4020 (4020–4020) 3641 (3074–4164) 0.46
51.6 (14–97) 88.0 (88.0–88.0) 59.5 (16–94) 0.55
14.3% (1/7) 0% (0/1) 0% (0/6) 0.91
14.3% (1/7) 0% (0/1) 0% (0/6) 0.37
85.7% (6/7) 0% (0/1) 0% (0/6) 0.03
57.1% (4/7) 100% (1/1) 0% (0/6) 0.06
0% (0/7) 0% (0/1) 0% (0/6) 0.84
0% (0/7) 0% (0/1) 0% (0/6) n/a
2.0 (0–4) 1.0 (1–1) 0 (0–0) 0.003
T. Prior, S. Kumar / European Journal of Obstetrics & Gynecology and Reproductive Biology 181 (2014) 135–139 139
compromise. This incidence was similar to that of cases in whichoperative delivery was performed due to concerns regarding fetalwellbeing, suggesting that minor deviations of the Apgar score fromnormal may be precipitated by the process of delivery itself, and arenot necessarily indicative of fetal compromise during labor.
Both umbilical artery pH and base deficit at birth, indicative offetal acidosis, are reported to be predictive of subsequent morbidity,however, both markers exhibit a strong dose–response relationshipwith subsequent outcomes [15,20]. Data from the current studydemonstrates that deviation from normality for both these measuresoccurs frequently amongst neonates delivered by instrumentaldelivery for a prolonged 2nd stage (pH <7.20 in 25% of case, baseexcess �8.0 in 22.9% of cases), cases where no concern regarding fetalwellbeing was implied by monitoring throughout labor.
To facilitate comparison between mode of delivery groups inthis study, the low thresholds defining adverse neonatal outcomeswere chosen deliberately. We do not suggest that these thresholdsbe used in clinical assessment, or that the composite risk scoreused here is a more appropriate tool for fetal assessment.
Results from this study do suggest that commonly usedneonatal outcome variables can be significantly influenced bythe process of delivery itself, as well as events occurring in the firststage of labor. In cases of intra-partum fetal compromise, conditionat birth is improved by prompt recognition and delivery. As aresult, the use of these measures alone to diagnose intra-partumfetal compromise may omit those cases where compromise wasidentified and managed appropriately. Conversely, even in caseswith normal CTG monitoring (accepted to have excellent negativepredictive value) [21], deviations from normal neonatal outcomesoccur frequently, particularly amongst cases delivered by instru-mental delivery. Whilst the neonatal outcomes reported here arevaluable in assessing the condition of the neonate at delivery, thereis significant potential for them to be confounded by the process ofdelivery itself. As a result when assessed in isolation, these markerscan neither confirm nor refute the presence of intra-partum fetalcompromise, and their use solely for this purpose in clinicalresearch should be discouraged.
Conflict of interest statement
The authors declare no conflict of interests.
Condensation
Mode of delivery, as well as fetal condition throughout labor,has a significant impact on neonatal outcome variables used toassess neonatal condition at birth.
Acknowledgements
We would like to thank The Moonbeam Trust (Registeredcharity No. 1110691) for funding this study.
References
[1] Clark SL, Hankins GDV. Temporal and demographic trends in cerebral palsy—fact and fiction. Am J Obstet Gynecol 2003;188(3):628–33.
[2] Blair E, Stanley F. Intrapartum asphyxia: a rare cause of cerebral palsy. J Pediatr1988;112(4):515–9.
[3] Graham EM, Ruis KA, Hartman AL, et al. A systematic review of the role ofintrapartum hypoxia-ischemia in the causation of neonatal encephalopathy.Am J Obstet Gynecol 2008;199(6):587–95.
[4] Okereafor A, Allsop J, Counsell SJ, et al. Patterns of brain injury in neonatesexposed to perinatal sentinel events. Pediatrics 2008;121(5):906–14.
[5] Nelson KB, Dambrosia JM, Ting TY, et al. Uncertain value of electronic fetalmonitoring in predicting cerebral palsy. N Engl J Med 1996;334(10):613–9.
[6] Conner SN, Tuuli MG, Longman RE, et al. Impact of obesity on incision-to-delivery interval and neonatal outcomes at cesarean delivery. Am J ObstetGynecol 2013;209(4):386. e1-6.
[7] Richardson BS, Czikk MJ, daSilva O, et al. The impact of labor at term onmeasures of neonatal outcome. Am J Obstet Gynecol 2005;192(1):219–26.
[8] Perlman JM. Intrapartum hypoxic–ischemic cerebral injury and subsequentcerebral palsy: medicolegal issues. Pediatrics 1997;99(6):851–9.
[9] Alkiaat A, Hutchinson M, Jacques A, et al. Evaluation of the frequency andobstetric risk factors associated with term neonatal admissions to special careunits. Aust NZ J Obstet Gynaecol 2013;53(3):277–82.
[10] Zanardo V, Simbi AK, Franzoi M, et al. Neonatal respiratory morbidity risk andmode of delivery at term: influence of timing of elective Caesarean delivery.Acta Paediatr 2004;93(5):643–7.
[11] Prior T, Mullins E, Bennett P, et al. Umbilical venous flow rate in term fetuses:can variations in flow predict intrapartum compromise? Am J Obstet Gynecol2013. http://dx.doi.org/10.1016/j.ajog.2013.08.042 [Epub ahead of print].
[12] NICE. Clinical guideline 55: intrapartum care. NICE; 2007.[13] Odd DE, Doyle P, Gunnell D, et al. Risk of low Apgar score and socioeconomic
position: a study of Swedish male births. Acta Paediatr 2008;97(9):1275–80.[14] Odd D, Lewis G, Gunnell D, et al. Risk of low Apgar scores and socioeconomic
status over a 30-year period. J Matern Fetal Neonatal Med 2013.[15] Low JA, Lindsay BG, Derrick EJ. Threshold of metabolic acidosis associated with
newborn complications. Am J Obstet Gynecol 1997;177(6):1391–4.[16] Bloom S, Leveno K, Spong C, et al. Decision-to-incision times and maternal and
infant outcomes. Obstet Gynecol 2006;108(1):6–11.[17] Janbu T, Nesheim B. Uterine artery blood velocities during contractions in
pregnancy and labour related to intrauterine pressure. Br J Obstet Gynaecol1987;94(12):1150–5.
[18] Ehrenstein V. Association of Apgar scores with death and neurologic disability.Clin Epidemiol 2009;9(1):45–53.
[19] Mercuri E, Rutherford M, Barnett A, et al. MRI lesions and infants with neonatalencephalopathy. Is the Apgar score predictive? Neuropediatrics2002;33(3):150–6.
[20] Malin GL, Morris RK, Khan KS. Strength of association between umbilical cordpH and perinatal and long term outcomes: systematic review and meta-analysis. BMJ 2010;13:340. c1471.
[21] Low J, Victory R, Derrick E. Predictive value of electronic fetal monitoring forintrapartum fetal asphyxia with metabolic acidosis. Obstet Gynecol1999;93(2):285–91.