Umbilical cord pH and base excess values in relation to adverse outcome events for infants delivering at term

Fatores de risco maternos associados à acidose fetal

OBJETIVOS: avaliar os fatores de risco maternos associados à acidose fetal. MÉTODOS: estudo tipo caso-controle composto por 188 recém-nascidos, sendo que 47 compuseram o grupo casos (pH de artéria umbilical <7,0) e 141 os de controles (pH de artéria umbilical <7,1 <7,3) nascidos imediatamente após cada caso. Consideraram-se fatores de inclusão: recém-nascidos de gestações únicas e sem malformação congênita. Analisaram-se variáveis maternas e fetais. Foram realizadas a Odds Ratio bruta e ajustada, teste t de Student, teste do qui-quadrado e análise multivariada através da regressão logística nãocondicional pelo método Enter. Assumiu-se como nível de significância estatística um p<0,05. RESULTADOS: no grupo de casos foi observado maior percentual de cesarianas, de recém-nascidos pré-termo, que apresentaram quase cinco vezes mais necessidade de cuidados intensivos e vinte cinco vezes mais chance de Apgar no 5º minuto <7. Não foram observadas associação entre os grupos e a apresentação fetal, idade materna, história de abortos anteriores, escolaridade materna e frequência ao pré-natal. Após a análise multivariada persistiram como fator de risco complicações relacionadas com a placenta e cordão. Os recémnascidos cujos partos associaram-se a complicações da placenta ou do cordão umbilical apresentaram três vezes mais chance de acidemia fetal. CONCLUSÕES: os recém-nascidos acidóticos estiveram relacionados à maior percentual de cesarianas, de prematuridade, necessidade de cuidados de tratamento intensivo e índice de Apgar <7 no 5º minuto. Após a análise multivariada, persistiram como fator de risco para acidemia fetal as complicações relacionadas ao descolamento prematuro de placenta e cordão umbilical.

[Cerebral palsy and perinatal asphyxia (I--diagnosis)]

Cerebral palsy (CP) is a group of disorders of the development of movement and posture, causing activity limitations, that are attributed to nonprogressing disturbances that occurred in the developing fetal or infant brain. The motor abnormalies are often accompanied by disturbances of sensation, perception, cognition, behavior and/or by a seizure disorder. The prevalence of CP has not decreased in developed countries over the past 30 years, despite the widespread use of electronic fetal heart rate monitoring and a 5- to 6-fold increase in the cesarean delivery rate. In the term newborn, CP may be attributed to perinatal asphyxia in case of metabolic acidosis in the cord blood (pH<7,00 and base deficit>12 mmol/L), followed by a moderate or severe neonatal encephalopathy within 24 hours and a further neurological impairement characterized by spastic quadriplegia and dyskinesia/dystonia. Dating the time of fetal asphyxia during delivery is possible when there are acute catastrophic complications during labor and unexpected acute or progressive fetal heart rate anomalies after a normal admission test, when there is a need for intensive neonatal resuscitation, a multi-organ failure within 72 hours of birth and visualization of acute non focal cerebral abnormalities, mainly by early magnetic resonance imaging (MRI). MRI sequences show either a brain-damaged pattern of the central basal ganglia, thalami and posterior limbs of internal capsules with relative cortical sparing, in acute, near-total asphyxial insults manifested by a continuous bradycardia or a pattern of cortical injury in the watershed zones and relative sparing of the central grey matter, in prolonged partial asphyxia, manifested by late or atypical variable decelerations with progressive fetal tachycardia, loss of reactivity and absent fluctuation. Prolongation of either type of asphyxial insult results in more global brain damage. In order to differentiate a CP occurring after perinatal asphyxia from other neurological sequelae in relation with infection, hemorrhage, stroke, malformations, genetic or metabolic diseases, it is essential that a definitive information from the brain by MRI and an extensive histological examination of the placenta are at disposal.

Oxygen utilization in newborns at delivery

AIMS

To evaluate the arteriovenous (AV) pH difference in cord blood as a possible indicator of fetal O(2)-utilization at delivery. Furthermore to examine which maternal, fetal and obstetrical factors lead to elevated O(2)-utilization.

METHODS

In this retrospective study all singleton live births, delivered within a four-month period at the University Hospital in Innsbruck, Austria, were analyzed. In total 491 deliveries were evaluated. Arterial and venous cord blood samples were collected at birth and analyzed by using a Radiometer ABL 510.

RESULTS

Spontaneous deliveries showed a highly significant elevation in AV-difference (pH 0.10) as compared to cesarean sections (pH 0.05). In spontaneous births, the AV-difference was high in the case of low arterial cord blood pH (P<0.01), as well as in nuchal cord (P<0.01), high parity (P<0.01), very short labor (P<0.05) and elevated birth size and weight (P<0.05).

CONCLUSIONS

As a result of increased fetal stress at birth, spontaneous delivery leads to higher O(2)-utilization than cesarean section, which is detectable in an elevated AV-difference. The AV-difference in combination with absolute pH-values can be used for the objective evaluation of fetal O(2)-utilization and consecutively the fetal stress at birth.

Neonatal neurological morbidity associated with uterine rupture

AIMS

To compare neonatal neurological morbidity associated with uterine rupture with morbidity associated with a non-reassuring fetal status.

METHODS

We conducted a retrospective cohort analysis. Twenty-one cases of term infants delivered after a symptomatic uterine rupture were analyzed and compared with a randomly selected group of 63 infants born after a non-reassuring fetal heart rate pattern.

RESULTS

Prevalence of uterine rupture was 0.058%. Maternal factors and infant general data were similar in both groups. Infants delivered after a uterine rupture had lower Apgar scores at 1 and 5 min, lower umbilical blood pH, and required more advanced resuscitation than infants delivered after a non-reassuring fetal status. Prevalence of hypoxic-ischemic encephalopathy in the uterine rupture group was 33%, compared with 5% in the other group (P<0.01, relative risk 3.7). Four infants in the uterine rupture group (19%) had moderate or severe encephalopathy; all of them had also multisystem dysfunction and an adverse outcome. No infant in the non-reassuring fetal status group showed moderate or severe encephalopathy.

CONCLUSIONS

Uterine rupture is a considerable sentinel event that involves a high rate of early and late neurological morbidity in the newborn infant.

Risk factors of neonatal respiratory distress following vaginal delivery and caesarean section in the German population

BACKGROUND

The incidence of caesarean section (CS) is steadily rising world-wide. In particular, CS on maternal demand is performed more frequently. In parts, this might be due to insufficient information of pregnant women about neonatal risks of CS. We sought to specify neonatal outcomes following different modes of delivery, i.e. vaginal delivery, primary CS and secondary CS and to define risk factors for respiratory morbidity and hospitalization.

METHODS

We analysed 2073 births (gestational age > 35 weeks) during a two-year period at a tertiary obstetric and neonatal centre in Germany. Statistical analyses were performed for single parameters by SPSS as well as by logistic regression to account for possible confounders. Furthermore, extensive model calculation was done.

RESULTS

Respiratory morbidity was increased following primary and secondary CS (p = 0.001). By multiple logistic regression, the strongest effect on respiratory symptoms was seen with gestational age, each week more in utero reducing the risk by an odds ratio (OR) of 0.69 (95% CI: [0.61; 0.79]; p = 1.9 x 10(-8)). Furthermore, a significant interaction between mode of delivery and gestational age was found for the risk of respiratory symptoms (p = 0.0035).

CONCLUSION

For every eight newborns delivered by primary CS one more than expected with vaginal delivery is hospitalized. It is highly relevant to recognize that each week of gestational age reduces the risk of respiratory symptoms, especially if primary CS is performed. The higher rate of respiratory morbidity and neonatal admission following CS should be clearly recognized in counselling of pregnant women.

A systematic review of the role of intrapartum hypoxia-ischemia in the causation of neonatal encephalopathy

The object of this review was to determine the incidence, morbidity, and mortality of an umbilical arterial pH < 7.0; the incidence of hypoxic-ischemic encephalopathy; and the proportion of cerebral palsy associated with intrapartum hypoxia-ischemia in nonanomalous term infants. A systematic review of the English language literature on the association between intrapartum hypoxia-ischemia and neonatal encephalopathy was conducted by using Pubmed and Embase. For nonanomalous term infants, the incidence of an umbilical arterial pH < 7.0 at birth is 3.7 of 1000, of which 51 of 297 (17.2%) survived with neonatal neurologic morbidity, 45 of 276 (16.3%) had seizures, and 24 of 407 (5.9%) died during the neonatal period. The incidence of neonatal neurologic morbidity and mortality for term infants born with cord pH < 7.0 was 23.1%. The incidence of hypoxic-ischemic encephalopathy is 2.5 of 1000 live births. The proportion of cerebral palsy associated with intrapartum hypoxia-ischemia is 14.5%. The vast majority of cases of cerebral palsy in nonanomalous term infants are not associated with intrapartum hypoxia-ischemia.

Intrapartum fetal ECG and diabetes

AIM

The objective of this study was to determine the prevalence and types of ST-segment changes of the fetal electrocardiogram (FECG) during labour in term fetuses born to mothers with diabetes mellitus (DM) or gestational diabetes.

METHODS

This was a retrospective case-control study involving populations from two multi centre trials: the Swedish Randomized Control Trial and the European Union ST-analysis (EU-STAN) trial. ST-segment changes were assessed in 104/309 cases and 207/468 controls from the Swedish and EU-STAN trials, respectively.

RESULTS

ST depression was present on the FECG in 22.1% of fetuses of mothers with DM compared to 12% of controls OR = 2.6, 95% CI = 1.4-4.7, p = 0.002 after adjusting for trial, birth weight, and nulliparity. ST elevation was present in 47.1% of DM patients and 41.2% of controls (OR = 1.4, 95% CI = 0.9-2.3, p = 0.18).

CONCLUSION

ST depression on the FECG was significantly more prevalent in the fetuses of mothers with DM, probably not indicating hypoxia but an altered ability of the myocardium to respond to the stress of labour. Further studies into the mechanism of fetal compromise during diabetic labour, are required.

Should prevention of chronic kidney disease start before pregnancy?

OBJECTIVE

The objective was to evaluate whether there is a role for the prevention of future chronic kidney disease (CKD) in children by improving maternal health at conception, this review addresses: the risk of childhood obesity in the development of CKD, trends in childhood obesity and body composition in children with renal diseases, trends in pre-pregnancy BMI and its association with neonatal outcome, and the effect of pre-pregnancy body mass index (BMI) on blood pressure and body composition in the offspring.

INCREASED BMI AND HYPERTENSION AS RISK FACTORS FOR CKD

It is now well established that the presence of hypertension increases the risk of CKD. Increased BMI can also increase the risk of the development of CKD indirectly, through an increase in the prevalence of hypertension, and, possibly, through a direct effect independent of hypertension.

TRENDS IN CHILDHOOD OBESITY IN GENERAL, AND SPECIFICALLY AMONG CHILDREN WITH RENAL DISEASES

An unprecedented epidemic of childhood obesity has been witnessed since the 1970s. An estimated 35% of children in North America are reported to be overweight. Children with CKD have even higher BMIs. TRENDS IN PRE-PREGNANCY BMI AND ITS ASSOCIATION WITH NEONATAL OUTCOME: The average BMI of mothers delivering in a single hospital in London, Ontario, rose from 24.3 kg/m2 in 1995 to 25.1 kg/m2 in 2004, whereas the average age of conception of the first child remained unchanged at 28 years. High pre-pregnancy BMIs increased the proportion of large-for-gestational-age newborns, a high proportion of congenital anomalies including renal abnormalities, and the need for Cesarean sections. EFFECT OF PRE-PREGNANCY BMI ON BLOOD PRESSURE AND BODY COMPOSITION IN THE OFFSPRING: Among 1,915 children (mean age 8.3 +/- 5.2 years), studied at the Children's Hospital, London Health Science Centre, BMI z-score correlated significantly with systolic (Spearman r = 0.214, P < 0.0001), and diastolic blood pressure z-scores (Spearman r = 0.143, P < 0.0001). The pre-pregnancy BMI correlated with both BMI z-score (Spearman r = 0.144, P < 0.0001) and blood pressure z-score (Spearman r = 0.13, P = 0.0005) in the children. The birth weight also correlated significantly with a higher BMI z-score (Spearman r = 0.134, P < 0.0001).

CONCLUSION

There are increasing trends in childhood obesity and pre-pregnancy maternal BMI. Higher pre-pregnancy BMI increases the risk for increased BMI z-score and blood pressure z-score in children. Since elevated BMI and blood pressure clearly are known risk factors of future CKD, targeting healthier weights prior to conception is likely to reduce the CKD burden in children.

The association of hypotonia and depression in the term and near-term neonate with metabolic acidemia

AIMS

To determine the association of hypotonia and depression in neonates at or near term with metabolic acidemia at birth (umbilical arterial pH<7.0 and base excess <-12 mM).

METHODS

This case-control study identified 87 infants without chromosomal or congenital abnormalities born at a single university hospital between 7/91 and 10/04 with hypotonia at birth requiring resuscitation and admission to the neonatal intensive care unit that had a cord gas at delivery. Controls were the subsequent delivery with a cord gas matched by gestational age.

RESULTS

Cases and controls did not differ in gestational age (38.7+/-1.9, 38.6+/-1.9 weeks) or birth weight (3,066+/-664, 3,171+/-655 g, P=0.20). Cases were more likely to have a cord pH<7.0 [17 (20%) vs. 1 (1.1%), P=0.0001] and cord pH 7.0-7.1 [13 (14.9%) vs. 2 (2.3%), P=0.003]. Among the hypotonic infants, 31 (35.6%) also were depressed at birth with a 5-min Apgar <7. In the depressed subset of hypotonic neonates 14/31 (45%) had a pH<7.0. Of the 12 hypotonic neonates with seizures, 3 (25%) had pH<7.0. Multivariate analysis showed a significant association between neonatal hypotonia and hypoglycemia, umbilical arterial pH, and nucleated red blood cell count.

CONCLUSIONS

Although metabolic acidemia is significantly associated with hypotonia at the time of birth, the majority of neonates with hypotonia and depression or seizures do not have objective evidence of asphyxia as measured by a cord gas at the time of delivery.

Use of umbilical cord blood gas analysis in the assessment of the newborn

Analysis of paired arterial and venous specimens can give insights into the aetiology of acidosis in the newborn

Predictors of umbilical artery acidosis in preterm delivery

OBJECTIVE

The purpose of this study was to investigate the significance of preterm acidosis and its risk factors.

STUDY DESIGN

From a cohort of 786 consecutive singleton neonates who were born after spontaneous or iatrogenic preterm delivery at 24.0-33.6 weeks of gestation from January 1993 to December 2005 with an evaluation of umbilical artery pH at delivery, we extracted demographic, obstetric, neonatal, and placental histologic variables and related them to umbilical artery evidence of fetal acidemia, which was defined as pH <7.10. Excluded were stillbirths and neonates with major congenital anomalies. Fetal distress was defined as nonreassuring fetal hearth rate tracing or biophysical profile or appearance of thick meconium at delivery. Statistical analysis included 1-way analysis of variance and logistic regression with a probability value of <.05 considered significant.

RESULTS

Neonates with umbilical cord evidence of acidosis (n = 34) were born more frequently after abruption (P < .001), fetal distress (P < .001), and by cesarean delivery (P < .04) and were born less frequently after a complete course of corticosteroids (P = .03) and labor (P = .05) than nonacidotic babies (n = 752). Acute inflammatory lesions at placental histologic evaluation were less frequent (P = .049), and placental vascular lesions were more common in acidotic than in nonacidotic preterm neonates (P = .039). Logistic regression analysis demonstrated that cord acidosis was associated independently with the occurrence of abruptio placentae (odds ratio, 7.3; 95% CI, 2.9, 18.8), fetal distress (odds ratio, 12.0; 95% CI, 4.9, 18.3), and vascular placental lesions (odds ratio, 2.8; 95% CI, 1.2, 6.8)

CONCLUSION

In preterm infants, umbilical artery acidosis is significantly more common in the presence of placental abruption, fetal distress, and histologic evidence of placental vascular disease.

Cord and placenta arterial gas analysis: the accuracy of delayed sampling

AIM

To determine the accuracy of delayed arterial gas sampling (1) from the umbilical cord and (2) from the placental surface at room temperature.

METHODS

Term deliveries were classified a priori into three groups: normal vaginal deliveries, elective caesarean sections and high risk deliveries. The cord was double clamped and paired arterial samples were taken from the cord and the placenta at 0, 30, 60 and 90 min.

RESULTS

90 placentas were sampled with 30 cases per group. At time 0 the mean cord pH 7.207 (+/-0.08) was significantly lower than the placenta pH 7.240 (+/-0.08). The cord pH dropped significantly: by 0.050 (95% CI 0.036 to 0.063) at 30 min, 0.087 (95% CI 0.069 to 0.105) at 60 min, and 0.112 (95% CI 0.086 to 0.138) at 90 min. The placenta pH fell at twice the rate of the cord pH over 90 min. At time 0 the mean cord base excess -7.0 mmol/l (+/-4.1) was significantly lower than the placenta base excess -6.3 mmol/l (+/-3.6). The cord base excess fell at 30 min by 4.1 mmol/l (95% CI 3.4 to 4.7), at 60 min by 7.1 mmol/l (95% CI 6.1 to 8.0), and at 90 min by 9.0 mmol/l (95% CI 7.9 to 10.0). The pH and base excess rate of fall was similar for each of the three delivery groups despite differing starting values.

CONCLUSION

Arterial blood gases should be taken as soon as possible after delivery from the umbilical cord. However, when this is not possible, the arterial pH and base excess from a delayed sample from a clamped cord at room temperature can be used to estimate the values at birth.

Elevated uterine activity increases the risk of fetal acidosis at birth

OBJECTIVE

The objective of the study was to assess the role of uterine activity on fetal outcome.

STUDY DESIGN

Intrauterine pressure (IUP) recordings from consecutive term singleton, vaginal deliveries collected between June 1, 1993, and July 1, 2004, were analyzed. One thousand four hundred thirty-three recordings were included. IUP data were obtained using HP 8040A and HP M1350 cardiotocographs. For each recording the uterine contraction curve was analyzed, and the following contraction parameters were determined: relaxation time; contraction duration, frequency, amplitude, and surface; Montevideo units; and active planimeter units and contraction frequency. IUP recordings and contraction parameters from deliveries ending with an umbilical artery pH of 7.11 or less were compared with those ending with an umbilical artery pH of 7.12 or greater. Statistical analyses were performed using Student's t test and logistic regression.

RESULTS

An umbilical artery pH 7.11 or less at birth is associated with significant more uterine activity during the first and second stage of labor.

CONCLUSION

Increased uterine activity is significantly associated with a higher incidence of an umbilical artery pH of 7.11 or less.

Fetal heart rate pattern notification guidelines and suggested management algorithm for intrapartum electronic fetal heart rate monitoring

CONTEXT

Numerous randomized controlled trials have demonstrated limited efficacy of intrapartum fetal heart rate monitoring in improving fetal outcome. A potential reason is the wide variability in clinical decision making seen with its use. Standardizing management of variant intrapartum fetal heart rate tracings may reduce this variability and lead to improvement in fetal outcome.

OBJECTIVE

We sought to develop notification guidelines and a management algorithm for variant intrapartum fetal heart rate tracings that improve fetal outcome and do not increase the operative delivery rate.

DESIGN

Outcomes for cases involving the use of our notification guidelines and management algorithm over six months (1181 deliveries) were compared with outcomes for historical control subjects (2247 deliveries).

MAIN OUTCOME MEASURES

The main outcome measures were Apgar scores <7 and the operative delivery rate.

RESULTS

We found no change in fetal outcome or operative delivery rate.

CONCLUSION

Our notification guidelines and management algorithm are safe and do not increase the operative delivery rate. A large multicenter trial is needed to demonstrate improvement in fetal outcome.

Base deficit estimation in umbilical cord blood is influenced by gestational age, choice of fetal fluid compartment, and algorithm for calculation

OBJECTIVE

The purpose of this study was to explore the influences of gestational age, the choice of fetal fluid compartment, and the algorithm for calculation on the estimation of the base deficit in umbilical cord arterial blood at birth.

STUDY DESIGN

From 1995 to 2002, cord arterial blood gases and obstetric data were available for 43,551 newborn infants at 37+ weeks of gestation (cohort I). The mean base deficit in blood and the base deficit in extracellular fluid were estimated from pH and PCO2 values in 28,213 newborn infants with a 5-minute Apgar score of > or = 9 (cohort II) with the use of 3 different calculation algorithms (base deficit in blood, base deficit in extracellular fluid [A], and base deficit in extracellular fluid [B]).

RESULTS

In cohort II, the base deficit in blood, the base deficit in extracellular fluid (A), and the base deficit in extracellular fluid (B) increased with advancing gestational age (linear regression; P < .0001). The curves run almost parallel, with the base deficit in blood being higher than the base deficit in extracellular fluid (A) and (B). With the use of receiver operating characteristic curves in cohort I, the area under curve to indicate a 5-minute Apgar score of < 7 and < 4 showed the area under curve-pH to be greater than the area under curve-base deficit in extracellular fluid (A) and (B), the area under curve-base deficit in blood to be greater than the area under curve-base deficit in extracellular fluid (A) and (B) for a 5-minute Apgar score of < 7, and the area under curve-base deficit in blood to be greater than the area under curve-base deficit in extracellular fluid (A) and (B) for an Apgar score of < 4. The cutoffs with highest sensitivity and lowest false-positive rate for a 5-minute Apgar score of < 7 and < 4 were, for both scores, a pH value of 7.15, a base deficit in blood of 10 mmol/L, a base deficit in extracellular fluid (A) of 8 mmol/L, and a base deficit in extracellular fluid (B) of 6 mmol/L.

CONCLUSION

The calculated values of the base deficit in umbilical cord arterial blood are influenced decisively by gestational age, the choice of fetal fluid compartment, and the calculation algorithms that are used. The power of the base deficit to indicate neonatal distress depends on the choices of fluid compartment and the algorithm that is used to calculate the base deficit.