Predictors of neonatal encephalopathy in full-term infants

Selection of babies for intervention after birth asphyxia

Based on animal experiments, the therapeutic window for neonates with signs of perinatal hypoxia-ischaemia is probably less than 6 h, and early selection of patients is of utmost importance. In term neonates, fetal heart rate and blood flow patterns, the Apgar score, and other clinical scoring systems are insufficient to select patients for intervention, whereas umbilical artery pH<7.0 combined with umbilical arteriovenous differences in PCO(2), lactate/pyruvate ratios in cord blood, and CSF interleukin-1beta have a better predictive value. At present, neurophysiological methods such as (amplitude-integrated) EEG and evoked potentials have the best predictive value. In preterm neonates, lactate/pyruvate and uric acid measurements in cord blood, as well as neurophysiology appear to be helpful to predict brain injury, and might be used to select patients for intervention.

Intrapartum maternal fever and neonatal outcome

OBJECTIVE

Much of fever during term labor may not be infectious but rather a consequence of the use of epidural analgesia. Therefore, we investigated the association of elevated maternal intrapartum temperature with neonatal outcome when the infant does not develop an infection.

METHODS

We studied 1218 nulliparous women with singleton, term pregnancies in a vertex presentation and spontaneous labor. Women were excluded if their temperature was >99.5 degrees F at admission for delivery, if they were diabetic or had an active genital herpes infection or if their infant developed a neonatal infection, had a congenital infection, or had a major malformation. Maximum intrapartum temperature was categorized as: </=100.4 degrees F (afebrile), 100.5 degrees F to 101 degrees F, and >101 degrees F.

RESULTS

During labor, 123 women (10.1%) developed a fever >100.4 degrees F; 62 (5.1%) women had a maximum temperature of 100.5 degrees F to 101 degrees F and 61 (5.0%) women had a maximum temperature >101 degrees F. Of febrile women, 97.6% had received epidural analgesia for pain relief. Infants of women developing a fever >100.4 degrees F were more likely to have a 1-minute Apgar score <7 (22.8% for >100.4 degrees F vs 8.0% for afebrile) and to be hypotonic after delivery (4.8% for >100.4 degrees F vs.5% for afebrile). Compared with infants of afebrile women, infants whose mothers' maximum temperature was >101 degrees F were more likely to require bag and mask resuscitation (11.5% vs 3.0%) and to be given oxygen therapy in the nursery (8.2% vs 1.3%). We also found a higher rate of neonatal seizure with fever (3.3% vs.2%), but the number of infants with seizure was small (n = 4). All associations remained essentially the same after controlling for confounding in logistic regression analyses.

CONCLUSIONS

Intrapartum maternal fever, particularly if >101 degrees F, was associated with a number of apparently transient adverse effects in the newborn. Larger studies are needed to investigate the association of intrapartum fever with neonatal seizures and to determine whether any lasting injury to the fetus may occur.

Stillbirths and neonatal encephalopathy in Kathmandu, Nepal: an estimate of the contribution of birth asphyxia to perinatal mortality in a low-income urban population

We describe a prospective cross-sectional survey over a 12-month period in the principal maternity hospital of Kathmandu, Nepal, where over 50% of the local population deliver. The study aim was to estimate the contribution of birth asphyxia to perinatal mortality in this setting. During 1995, there were 14,371 livebirths and 400 stillbirths, a total stillbirth rate of 27 per 1000 total births. The fresh term (2000 g or more) stillbirth rate was 8.5 per 1000 total births [95% CI 7.1, 10.1]. Ninety-two cases of neonatal encephalopathy (NE) affecting term infants were detected (excluding those due to congenital malformations, hypoglycaemia and early neonatal sepsis). The birth prevalence of NE was 6.4 per 1000 livebirths [95% CI 5.2, 7.8]. There was evidence of intrapartum compromise in 63 (68%) of the cases of NE and 65 (76%) of the stillbirths, but only in 12 (12%) of controls. The cause-specific early neonatal mortality rate for NE was 2.1 per 1000 livebirths [95% CI 1.4, 3.0]. Combining the NE deaths and fresh stillbirths gives an upper estimate for term birth asphyxia perinatal mortality rate of 10.8 per 1000 total births [95% CI 9.2, 12.6], 24% of all perinatal deaths before hospital discharge. This study suggests that birth asphyxia remains an important cause of perinatal mortality in developing countries. The paper discusses the pros and cons of different strategies to reduce birth asphyxia in low-income countries.

Antecedents of neonatal encephalopathy with fetal acidaemia at term

OBJECTIVE

To identify the relative contribution of antenatal hypoxia, obstetric catastrophe during labour and fetal monitoring practice to the occurrence of neonatal encephalopathy associated with acidaemia at term.

DESIGN

Prospective study.

SETTING

Tertiary referral hospital in Auckland, New Zealand.

SAMPLE

Twenty-two term babies born between January 1996 and October 1997 with umbilical artery pH < or = 7.09 (median 6.88) or 5 minute Apgar score < 7 (median 5.0), and moderate to severe encephalopathy within five hours of birth.

METHODS

Antenatal and intrapartum events and fetal heart rate monitoring practice were reviewed by an experienced obstetrician.

RESULTS

More than half the cases were associated with events beyond the control of the clinician: 5 of 22 (23%) had evidence of antenatal hypoxia and 5 of 22 (23%) experienced an obstetric catastrophe during labour. Use of continuous fetal monitoring techniques or the interpretation of fetal heart rate changes was suboptimal in 8 of 12 cases. Continuous monitoring was not performed at all in three cases. All pregnancies were of either low or medium risk; none had proteinuric hypertension and no case was breech, small for gestational age or had a gestational age > or = 42 weeks.

CONCLUSIONS

A significant proportion of babies with encephalopathy associated with acidaemia at term experienced either antenatal hypoxia or catastrophic events beyond the control of the clinician. Further improvements in obstetric care will require greater vigilance in low to medium risk pregnancies and improved fetal monitoring practice during both induction and labour.

Maternal fever and neonatal depression: preliminary observations

The objectives of this study were to determine in term infants: (1) the importance of maternal fever (maternal temperature > 38 degrees C) as a risk factor for neonatal depression and (2) the clinical course of infants admitted to the Neonatal Intensive Care Unit (NICU) born to mothers with fever. For 2 years, 59 (0.24%) of 25,000 term infants had a 5-minute Apgar score < or = 5 and 22 (0.08%) infants were administered chest compressions with or without epinephrine as part of cardiopulmonary resuscitation (CPR) in the delivery room. The perinatal event most commonly associated with a 5-minute Apgar score < or = 5 was maternal fever in 19 infants (32%), with meconium + fetal heart rate (FTHR) abnormalities in 15 (25%), and FTHR abnormalities only in 13 (22%), additional associations (n = 13). By stepwise linear regression analysis, a 5-minute Apgar < or = 5 was related only to the initial infant temperature (p = 0.009, r = 0.33). Maternal fever noted in six infants (27%) was also commonly associated with CPR, as was the presence of meconium + FTHR abnormalities in seven (32%), and FTHR abnormalities only in four (18%). One hundred thirteen (7.5%) of the approximately 1,500 term infants born to mothers with maternal fever were admitted to the NICU. In addition to fever, the labor was complicated by meconium (in 16 infants), meconium + FTHR abnormalities (in 19 infants), and FTHR abnormalities only (in 11 infants). Resuscitative interventions in the delivery room included oxygen only in 43 infants, bag and mask ventilation in 38, continuous positive airway pressure in 10, intubation in 16, and CPR in six infants. Forty-nine infants (43%) had an initial temperature > 38 degrees C including 13 (11%) with an initial temperature > 39 degrees C. Twelve (10%) infants remained intubated on admission and five required ventilator support > 24 hours. One blood culture was positive although all mothers were pretreated with antibiotics. One infant developed hypoxic ischemic encephalopathy including seizures. Maternal fever is the perinatal event most frequently associated with a 5-minute Apgar score < or = 5 and a common association with the need for CPR. Clinicians attending the delivery of a mother with fever should anticipate the potential for neonatal depression; such awareness should facilitate appropriate preparation before delivery and potentially reduce the need for more intensive resuscitation.

The neurologically impaired child and alleged malpractice at birth

Controlled studies, improved epidemiologic and statistical techniques, and an increase in biological information on mechanisms of fetal and neonatal brain injury or maldevelopment have led to a better, although still imperfect, understanding of the cause of developmental disabilities. The role of asphyxia during the birth process is smaller than was once believed. Intrauterine exposure to infection, autoimmune and coagulation disorders, and problems specific to multiple pregnancies are risk factors for cerebral palsy. Electronic fetal monitoring and other observations during birth are unsatisfactory management guides, having enormously high rates of false-positive identification. There is no evidence that caesarean section can prevent cerebral palsy in term infants.

Group B streptococcus infection, not birth asphyxia

This case illustrates 2 main points. Firstly, fetal infection can mimic exactly both the immediate and delayed signs of perinatal asphyxia. Secondly, the placenta may hold the key to the diagnosis of sepsis which may be made difficult in the neonate by labour ward practices such as the use of intrapartum and immediate newborn antibiotics. We strongly support the recommendation that newborn blood and fetal membrane cultures should always be obtained in babies with a diagnosis of 'intrapartum asphyxia and fetal distress' (1). To this we would add the recommendation that placental histology be performed in these circumstances.

Intrapartum risk factors for newborn encephalopathy: the Western Australian case-control study

OBJECTIVE

To identify intrapartum predictors of newborn encephalopathy in term infants.

DESIGN

Population based, unmatched case-control study.

SETTING

Metropolitan area of Western Australia, June 1993 to September 1995.

SUBJECTS

All 164 term infants with moderate or severe newborn encephalopathy; 400 randomly selected controls.

MAIN OUTCOME MEASURES

Adjusted odds ratio estimates.

RESULTS

The birth prevalence of moderate or severe newborn encephalopathy was 3.8/1000 term live births. The neonatal fatality was 9.1%. Maternal pyrexia (odds ratio 3.82), a persistent occipitoposterior position (4.29), and an acute intrapartum event (4.44) were all risk factors for newborn encephalopathy. More case infants than control infants were induced (41.5% and 30.5%, respectively) and fewer case infants were delivered by caesarean section without labour (3.7% and 14.5%, respectively). Operative vaginal delivery (2.34) and emergency caesarean section (2.17) were both associated with an increased risk. There was an inverse relation between elective caesarean section (0.17) and newborn encephalopathy. After application of a set of consensus criteria for elective caesarean section only three (7%) eligible case mothers compared with 33 (65%) eligible control mothers were sectioned electively. Of all the case infants, 113 (69%) had only antepartum risk factors for newborn encephalopathy identified; 39 (24%) had antepartum and intrapartum factors; eight (5%) had only intrapartum factors; and four (2%) had no recognised antepartum or intrapartum factors.

CONCLUSIONS

The causes of newborn encephalopathy are heterogeneous and many relate to the antepartum period. Elective caesarean section has an inverse association with newborn encephalopathy. Intrapartum hypoxia alone accounts for only a small proportion of newborn encephalopathy. These results question the view that most risk factors for newborn encephalopathy lie in the intrapartum period.

Antepartum risk factors for newborn encephalopathy: the Western Australian case-control study

OBJECTIVE

To ascertain antepartum predictors of newborn encephalopathy in term infants.

DESIGN

Population based, unmatched case-control study.

SETTING

Metropolitan area of Western Australia, June 1993 to September 1995.

SUBJECTS

All 164 term infants with moderate or severe newborn encephalopathy; 400 randomly selected controls.

MAIN OUTCOME MEASURES

Adjusted odds ratio estimates.

RESULTS

The birth prevalence of moderate or severe newborn encephalopathy was 3.8/1000 term live births. The neonatal fatality was 9.1%. The risk of newborn encephalopathy increased with increasing maternal age and decreased with increasing parity. There was an increased risk associated with having a mother who was unemployed (odds ratio 3.60), an unskilled manual worker (3.84), or a housewife (2.48). Other risk factors from before conception were not having private health insurance (3.46), a family history of seizures (2.55), a family history of neurological disease (2.73), and infertility treatment (4.43). Risk factors during pregnancy were maternal thyroid disease (9.7), severe pre-eclampsia (6.30), moderate or severe bleeding (3.57), a clinically diagnosed viral illness (2.97), not having drunk alcohol (2.91); and placenta described at delivery as abnormal (2.07). Factors related to the baby were birth weight adjusted for gestational age between the third and ninth centile (4.37) or below the third centile (38.23). The risk relation with gestational age was J shaped with 38 and 39 weeks having the lowest risk.

CONCLUSIONS

The causes of newborn encephalopathy are heterogeneous and many of the causal pathways start before birth.

[Definition of asphyxia neonatorum and incidence of neurologic and systemic complications in the full-term newborn]

PATIENTS AND METHODS

In a prospective multicentric study, 152 of 10,065 live term births had birth asphyxia, defined by the association of three indicators (fetal distress, depression at birth and metabolic acidosis).

RESULTS

The incidence of birth asphyxia was 1.5% of live term births when birth asphyxia was defined by the presence of at least two indicators, and 1% of live term births when birth asphyxia was defined by the association of metabolic acidosis and another indicator. Neurological complications were observed in 66 cases (43%). The incidence of post-asphyxial encephalopathy (PAE) was 5.9/1000 of live term births (mild PAE: 3/1000; moderate PAE: 2.7/1000; severe PAE: 0.2/1000). Systemic complications were observed in 87 patients (57%). Renal injury and coagulopathy were associated with moderate or severe PAE. Respiratory complications (39%), infections (17%) and gastro-intestinal intolerance (15%) often complicated the course. Severe complications were never seen in the absence of significant metabolic acidosis at 30 minutes of life.

CONCLUSION

Our study has many implications concerning the diagnosis of birth asphyxia and its complications. A terminology based on clinical observation and arterial pH evaluation is proposed in order to clarify the situation.

Thyroxine abuse: an unusual case of thyrotoxicosis in pregnancy

Eating disorders and the associated behavioural problems and drug abuse are uncommon in pregnancy. When they do occur they are often unrecognized because of denial but when significant may pose a risk to both the mother and her fetus. This case illustrates a number of problems that may be encountered in women with eating disorders in pregnancy, including prolonged and recurrent metabolic disturbances and diuretic abuse. In particular it illustrates the derangements of thyroid function seen in pregnant women with eating disorders and reminds us that when a cause for thyrotoxicosis remains obscure, thyroxine abuse should be considered and explored.

Newer concepts and approaches to neonatal brain asphyxia

The asphyxial injury to neonate brain seems to be mediated through a cascade of biochemical events during ischaemia--reperfusion which includes excitatory amino acids, free radicals and accelerated programmed cell death (Apoptosis). The diagnosis of asphyxia requires rigorous approach based on background clinical information, certain diagnostic tests and exclusion of alternative diagnosis which may have similar clinical presentation. The treatment currently employed for the management of birth asphyxia controversial and requires critical appraisal. The future strategies for management include a number of approaches based on putative mechanism for asphyxial brain injury but they are still being evaluated as research and should not be used for clinical purposes in human newborns as yet.

Prenatal determinants of motor disorders

Cerebral palsies (CP) are the commonest childhood motor disorders, originating in early childhood as a result of interference in the developing brain. Identifying prenatal factors in CP is a challenge because there is a considerable period of time (years) between the causal event(s) and diagnosis. Four fascinating "natural" situations provided a unique opportunity to identify and measure prenatal exposures in relation to motor disorders, thus establishing the unequivocal role of some factors. However, the majority of studies determining adverse reproductive effects of environmental factors require a retrospective case-control approach, which present considerable problems. Studies based on the Western Australian CP register suggest that prenatal factors singly or in complex sequences are more common as causes than those occurring perinatally or postnatally. In future, better diagnosis of motor disorders, use of sophisticated scientific techniques to identify markers of neuronal development and the accurate linkage of these findings to clinical patterns of motor dysfunction are required.

The intrapartum CTG prior to neonatal encephalopathy at term: a case-control study

OBJECTIVE

To compare cardiotocograph (CTG) records during labour in cases of neonatal encephalopathy and matched controls.

DESIGN

Case-control study.

SETTING

Metropolitan area of Perth, Western Australia.

SUBJECTS

Term deliveries complicated by neonatal encephalopathy and controls matched for sex, hospital, time of birth, day of week of birth and maternal health insurance.

MAIN OUTCOME MEASURES

Low fetal heart rate (FHR) variability, FHR accelerations, late decelerations, total Kreb's score and FIGO classification of CTG records.

RESULTS

The neonatal encephalopathy group had significantly more abnormal CTG records (89%) classified according to FIGO, although 52% of control CTG records were also abnormal. CTG records from cases developed significant differences in terms of absence of FHR accelerations and low FHR variability, but not late decelerations, prior to delivery.

CONCLUSION

Given the low incidence of neonatal encephalopathy in this study (7 per 1000) the predictive value of an abnormal CTG record is clinically unhelpful. However, the changes in the FHR in such cases suggest a greater disturbance of fetal (rest-activity) behaviour during labour.