Changing two-year outcome of infants weighing 500 to 999 grams at birth: a hospital study

Trends in survival, perinatal morbidities and two-year neurodevelopmental outcomes in extremely low-birthweight infants over four decades

BACKGROUND

Although outcomes for infants born extremely low birthweight (ELBW; <1000 g birthweight) have improved over time, it is important to document survival and morbidity changes following the advent of modern neonatal intensive care in the 1990s.

OBJECTIVE

To describe trends in survival, perinatal outcomes and neurodevelopment to 2 years' corrected age over time across six discrete geographic cohorts born ELBW between 1979 and 2017.

METHODS

Analysis of data from discrete population-based prospective cohort studies of all live births free of lethal anomalies with birthweight 500-999 g in the state of Victoria, Australia, over 6 eras: 1979-80, 1985-87, 1991-92, 1997, 2005 and 2016-17. Perinatal data collected included survival, duration and type of respiratory support, neonatal morbidities and two-year neurodevelopmental outcomes.

RESULTS

More ELBW live births were inborn (born in a maternity hospital with a neonatal intensive care unit) over time (1979-80, 70%; 2016-17, 84%), and more were offered active care (1979-80, 58%; 2016-17, 90%). Survival to 2 years rose substantially, from 25% in 1979-80 to 80% in 2016-17. In survivors, rates of any assisted ventilation rose from 75% in 1979-80 to 99% in 2016-17. Cystic periventricular leukomalacia, severe retinopathy of prematurity and blindness improved across eras. Two-year data were available for 95% (1054/1109) of survivors. Rates of cerebral palsy, deafness and major neurodevelopmental disability changed little over time. The annual numbers with major neurodevelopmental disability increased from 12.5 in 1979-80 to 30 in 2016-17, but annual numbers free of major disability increased much more, from 31 in 1979-80 to 147 in 2016-17.

CONCLUSIONS

Active care and survival rates in ELBW children have increased dramatically since 1979 without large changes in neonatal morbidities. The numbers of survivors free of major neurodevelopmental disability have increased more over time than those with major disability.

Antimicrobial-impregnated central venous catheters for preventing neonatal bloodstream infection: the PREVAIL RCT

BACKGROUND

Clinical trials show that antimicrobial-impregnated central venous catheters reduce catheter-related bloodstream infection in adults and children receiving intensive care, but there is insufficient evidence for use in newborn babies.

OBJECTIVES

The objectives were (1) to determine clinical effectiveness by conducting a randomised controlled trial comparing antimicrobial-impregnated peripherally inserted central venous catheters with standard peripherally inserted central venous catheters for reducing bloodstream or cerebrospinal fluid infections (referred to as bloodstream infections); (2) to conduct an economic evaluation of the costs, cost-effectiveness and value of conducting additional research; and (3) to conduct a generalisability analysis of trial findings to neonatal care in the NHS.

DESIGN

Three separate studies were undertaken, each addressing one of the three objectives. (1) This was a multicentre, open-label, pragmatic randomised controlled trial; (2) an analysis was undertaken of hospital care costs, lifetime cost-effectiveness and value of information from an NHS perspective; and (3) this was a retrospective cohort study of bloodstream infection rates in neonatal units in England.

SETTING

The randomised controlled trial was conducted in 18 neonatal intensive care units in England.

PARTICIPANTS

Participants were babies who required a peripherally inserted central venous catheter (of 1 French gauge in size).

INTERVENTIONS

The interventions were an antimicrobial-impregnated peripherally inserted central venous catheter (coated with rifampicin-miconazole) or a standard peripherally inserted central venous catheter, allocated randomly (1 : 1) using web randomisation.

MAIN OUTCOME MEASURE

Study 1 - time to first bloodstream infection, sampled between 24 hours after randomisation and 48 hours after peripherally inserted central venous catheter removal. Study 2 - cost-effectiveness of the antimicrobial-impregnated peripherally inserted central venous catheter compared with the standard peripherally inserted central venous catheters. Study 3 - risk-adjusted bloodstream rates in the trial compared with those in neonatal units in England. For study 3, the data used were as follows: (1) case report forms and linked death registrations; (2) case report forms and linked death registrations linked to administrative health records with 6-month follow-up; and (3) neonatal health records linked to infection surveillance data.

RESULTS

Study 1, clinical effectiveness - 861 babies were randomised (antimicrobial-impregnated peripherally inserted central venous catheter, n = 430; standard peripherally inserted central venous catheter, n = 431). Bloodstream infections occurred in 46 babies (10.7%) randomised to antimicrobial-impregnated peripherally inserted central venous catheters and in 44 (10.2%) babies randomised to standard peripherally inserted central venous catheters. No difference in time to bloodstream infection was detected (hazard ratio 1.11, 95% confidence interval 0.73 to 1.67; p = 0.63). Secondary outcomes of rifampicin resistance in positive blood/cerebrospinal fluid cultures, mortality, clinical outcomes at neonatal unit discharge and time to peripherally inserted central venous catheter removal were similar in both groups. Rifampicin resistance in positive peripherally inserted central venous catheter tip cultures was higher in the antimicrobial-impregnated peripherally inserted central venous catheter group (relative risk 3.51, 95% confidence interval 1.16 to 10.57; p = 0.02) than in the standard peripherally inserted central venous catheter group. Adverse events were similar in both groups. Study 2, economic evaluation - the mean cost of babies' hospital care was £83,473. Antimicrobial-impregnated peripherally inserted central venous catheters were not cost-effective. Given the increased price, compared with standard peripherally inserted central venous catheters, the minimum reduction in risk of bloodstream infection for antimicrobial-impregnated peripherally inserted central venous catheters to be cost-effective was 3% and 15% for babies born at 23-27 and 28-32 weeks' gestation, respectively. Study 3, generalisability analysis - risk-adjusted bloodstream infection rates per 1000 peripherally inserted central venous catheter days were similar among babies in the trial and in all neonatal units. Of all bloodstream infections in babies receiving intensive or high-dependency care in neonatal units, 46% occurred during peripherally inserted central venous catheter days.

LIMITATIONS

The trial was open label as antimicrobial-impregnated and standard peripherally inserted central venous catheters are different colours. There was insufficient power to determine differences in rifampicin resistance.

CONCLUSIONS

No evidence of benefit or harm was found of peripherally inserted central venous catheters impregnated with rifampicin-miconazole during neonatal care. Interventions with small effects on bloodstream infections could be cost-effective over a child's life course. Findings were generalisable to neonatal units in England. Future research should focus on other types of antimicrobial impregnation of peripherally inserted central venous catheters and alternative approaches for preventing bloodstream infections in neonatal care.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN81931394.

FUNDING

This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 57. See the NIHR Journals Library website for further project information.

Are outcomes of extremely preterm infants improving? Impact of Bayley assessment on outcomes

OBJECTIVES

To compare 18- to 22-month cognitive scores and neurodevelopmental impairment (NDI) in 2 time periods using the National Institute of Child Health and Human Development's Neonatal Research Network assessment of extremely low birth weight infants with the Bayley Scales of Infant Development, Second Edition (Bayley II) in 2006-2007 (period 1) and using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley III), with separate cognitive and language scores, in 2008-2011 (period 2).

STUDY DESIGN

Scores were compared with bivariate analysis, and regression analyses were run to identify differences in NDI rates.

RESULTS

Mean Bayley III cognitive scores were 11 points higher than mean Bayley II cognitive scores. The NDI rate was reduced by 70% (from 43% in period 1 to 13% in period 2; P < .0001). Multivariate analyses revealed that Bayley III contributed to a decreased risk of NDI by 5 definitions: cognitive score <70 and <85, cognitive or language score <70; cognitive or motor score <70, and cognitive, language, or motor score <70 (P < .001).

CONCLUSION

Whether the Bayley III is overestimating cognitive performance or whether it is a more valid assessment of emerging cognitive skills than the Bayley II is uncertain. Because the Bayley III identifies significantly fewer children with disability, it is recommended that all extremely low birth weight infants be offered early intervention services at the time of discharge from the neonatal intensive care unit, and that Bayley scores be interpreted with caution.

Outcomes at age 2 years of infants < 28 weeks' gestational age born in Victoria in 2005

OBJECTIVE

To determine the survival rates and neurosensory outcomes of infants born at gestational age 22-27 weeks in the state of Victoria in 2005 and compare theses data with those for similar infants born in the 1990s.

STUDY DESIGN

This was a population-based study of all extremely preterm (22-27 weeks' gestational age) live births in Victoria in 2005 free of lethal anomalies and randomly selected term controls. Survival and quality-adjusted survival rates at age 2 years were determined relative to the controls, and results were compared with regional extremely preterm cohorts born in 1991-92 and 1997.

RESULTS

Of 270 very preterm live births in 2005, 172 (63.7%) survived to 2 years, not significantly different from the survival rate of 69.6% for those born in 1997. Rates of severe developmental delay and severe disability were lower than in the very preterm survivors born in 1997. Quality-adjusted survival rates in the extremely preterm cohorts rose from 42.1% in 1991-92 to 55.1% in 1997, but did not increase in 2005 (53.4%).

CONCLUSIONS

Survival rates for infants born at 22-27 weeks' gestational age have not increased since the late 1990s, but the neurosensory outcome in survivors has improved.

Outcome of extreme prematurity: a prospective comparison of 2 regional cohorts born 20 years apart

OBJECTIVE

To determine changes that have occurred over the past 20 years in perinatal characteristics, neonatal treatments, morbidities, and early neurodevelopmental outcomes of infants born at < or =30 weeks' gestation.

METHODS

This was a prospective regional study including all live-born infants < or =30 weeks' gestation born between July 1985 and June 1986 (cohort 1) and July 2005 and June 2006 (cohort 2). Sociodemographically matched term controls were recruited for each cohort. Perinatal characteristics, mortality rates, and survival with and without impairments at 24 months' corrected age were compared.

RESULTS

There was a 35% increase in the number of live-born preterm births (138 in cohort 1 and 187 in cohort 2) despite a >10% decline in total births in the region (P < .001). Assisted fertility (rarely available for mothers in cohort 1) was responsible for 20% of pregnancies in cohort 2. Survival to hospital discharge increased over 20 years from 82% to 93% (P = .002), primarily because of higher survival for infants born at <27 weeks' gestation (63% vs 88%; P = .004). Changes in management in cohort 2 included the use of surfactant (62% of infants) and increased use of postnatal steroids (39% vs 9%; P < .001), that were associated with a shorter median duration of mechanical ventilation (13 vs 21 days; P < .001); however, the incidence of bronchopulmonary dysplasia was higher in cohort 2 (56% vs 35%; P < .001). There was a significant decrease in incidence of severe ultrasound abnormalities from 17% in cohort 1 to 7% in cohort 2 (P = .008). At 24 months of age, 7% of cohort 1 and 5% of cohort 2 had an abnormal neurologic exam. Bayley cognitive scores were improved in cohort 2 (significantly closer to the mean of their controls). As a result, survival without severe neurodevelopmental impairment increased from 62% in cohort 1 to 81% in cohort 2 (P < .001).

CONCLUSION

Over 20 years, there has been a significant increase in live births at < or =30 weeks' gestational age, with a greater percentage of these neonates surviving without severe neurodevelopmental impairment at 24 months.

Neonatal intensive care at borderline viability--is it worth it?

BACKGROUND

Very preterm infants at the borderline of viability, especially those <25 weeks of gestational age, have survived in increasing numbers in recent years, but concerns persist about their long-term outcome and their consumption of scarce hospital resources.

AIMS

To determine incremental changes in long-term outcome and consumption of resources by very preterm infants in the 1990s.

DESIGN

Cohort study.

PATIENTS

Consecutive livebirths with gestational ages 23-27 weeks born in the state of Victoria in two discrete eras, 1991-1992 (n=401) and 1997 (n=208), and randomly selected contemporaneous normal birthweight (NBW, birthweight >2499 g) controls (1991-1992 n=265, 1997 n=198).

MAIN OUTCOME MEASURES

Survival, and neurosensory impairments, disabilities and utilities, and consumption of hospital resources to 2 years of age.

RESULTS

Compared with 1991-1992, in 1997 more infants were offered intensive care and the survival rate was higher at each week of gestation, and overall (absolute increase in survival 16%; 95% confidence interval, 8%, 24%). The largest increases in the survival and quality-adjusted survival rates were in infants at 23 weeks (31% and 20%, respectively). The incremental resource costs of improving survival and quality-adjusted survival were similar in infants of 23-24 weeks compared with those of 25-27 weeks (e.g., 112 vs. 105 days of assisted ventilation per additional survivor, or 167 vs. 180 days of assisted ventilation per additional quality-adjusted survivor, respectively).

CONCLUSIONS

Increased intensive care in the late 1990s for infants at the borderline of viability was associated with improved outcomes, at incremental costs that were not excessive compared with slightly more mature infants.

Changing availability of neonatal intensive care for extremely low birthweight infants in Victoria over two decades

OBJECTIVE

To determine the changes in availability of neonatal intensive care for extremely low birthweight (ELBW) infants, and the consequences of a lack of availability.

DESIGN AND SETTING

Population-based cohort study of consecutive ELBW infants born in the state of Victoria during four distinct eras.

PARTICIPANTS

All livebirths weighing 500-999 g in Victoria in the calendar years 1979-1980 (n = 351), 1985-1987 (n = 560), 1991-1992 (n = 429), and 1997 (n = 233).

MAIN OUTCOME MEASURES

Changes over time in the proportions of ELBW infants offered intensive care, the proportions that were "outborn" (born outside level 3 perinatal centres), and their survival rates and quality of survival compared with "inborn" infants.

RESULTS

The proportions of ELBW infants offered intensive care increased over time and were significantly higher in heavier infants. The proportion of outborn ELBW infants was 30% in 1979-1980, falling to 9% by 1997. The difference in survival rates between inborn and outborn infants widened progressively over time: the survival advantages for inborn infants over outborn infants were 12.0% in 1979-1980, 30.1% in 1985-1987, 36.5% in 1991-1992, and 43.6% in 1997. For survivors, the quality of life was significantly better for inborn infants in two of the four eras.

CONCLUSIONS

Neonatal intensive care has been increasingly available for ELBW infants in Victoria over the period 1979 to 1997. The gap in survival rates between outborn and inborn infants has widened, and the quality of life of outborn survivors is inferior.

Evaluation of neonatal intensive care for extremely low birth weight infants in Victoria over two decades: I. Effectiveness

CONTEXT

Although individual components of neonatal intensive care have proven efficacy, doubts remain about its overall effectiveness.

OBJECTIVE

To determine the changes in effectiveness of neonatal intensive care for extremely low birth weight (ELBW) infants over 2 decades.

DESIGN

Population-based cohort study of consecutive ELBW infants born during 4 distinct eras: 1979-1980, 1985-1987, 1991-1992, and 1997, all followed to at least 2 years of age.

SETTING

The state of Victoria, Australia.

PATIENTS

All ELBW live births of birth weight 500 to 999 g in the state in the calendar years indicated (1979-1980 [n = 351]; 1985-1987 [n = 560]; 1991-1992 [n = 429]; 1997 [n = 233]). Survivors were assessed at 2 years of age by pediatricians and psychologists blinded to perinatal details. The follow-up rates were high for each ELBW cohort (1979-1980: 100% [89 of 89]; 1985-1987: 100% [212 of 212]; 1991-1992: 98% [237 of 241]; 1997: 99% [168 of 170]).

MAIN OUTCOME MEASURES

Survival and quality-adjusted survival rates at 2 years of age.

RESULTS

The survival rate to 2 years of age improved significantly between successive eras (absolute increase and 95% confidence interval: 1985-1987 vs 1979-1980, 12.5% and 6.3%-18.4%; 1991-1992 vs 1985-1987, 18.3% and 12.1%-24.4%; 1997 vs 1991-1992, 16.8% and 9.2%-23.9%), as did the quality-adjusted survival rate (absolute increase: 1985-1987 vs 1979-1980, 12.4%; 1991-1992 vs 1985-1987, 13.8%; 1997 vs 1991-1992, 13.2%). Overall, the survival rate increased from approximately 1 in 4 (25%) in 1979-1980 to 3 in 4 (73%) in 1997, and the quality-adjusted survival rate also increased threefold, from 19% in 1979-1980 to 59% in 1997. The biggest gains in survival and quality-adjusted survival in the most recent era were in infants in lighter birth-weight subgroups.

CONCLUSION

The effectiveness of neonatal intensive care for ELBW infants in Victoria improved progressively from the late 1970s to the late 1990s.

Longitudinal multicenter follow-up of high-risk infants: why, who, when, and what to assess

This article reviews experience with longitudinal follow-up of high-risk infants in the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network. In 1993, the Network initiated a research protocol to provide longitudinal follow-up of infants with birth weight less than 1001 g and infants with higher birth weights who participated in certain Network randomized trials. Infants are assessed at 18 to 22 months corrected age (corrected for degree of prematurity) using measures of the infant's health, growth, neuromotor, and early cognitive functioning, language, behavior, and family resources. Data from these assessments have been used to investigate potentially modifiable risk factors for cerebral palsy and delayed early cognitive functioning and to evaluate the risks and benefits of interventions assessed in randomized trials. The Network's experience thus far suggests that longitudinal follow-up can provide valuable information about treatments given to fetuses and neonates.

Longitudinal motor development of "apparently normal" high-risk infants at 18 months, 3 and 5 years

BACKGROUND

Motor development appears to be more affected by premature birth than other developmental domains, however few studies have specifically investigated the development of gross and fine motor skills in this population.

AIM

To examine longitudinal motor development in a group of "apparently normal" high-risk infants.

SETTING

Developmental follow-up clinic in a perinatal centre.

STUDY DESIGN

Longitudinal observational cohort study.

SUBJECTS

Fifty-eight infants born less than 29 weeks gestation and/or 1000 g and without disabilities detected at 12 months.

OUTCOME MEASURES

Longitudinal gross and fine motor skills at 18 months, 3 and 5 years using the Peabody Developmental Motor Scales. The HOME scale provided information of the home environment as a stimulus for development.

RESULTS

A large proportion (54% at 18 months, 47% at 3 years and 64% at 5 years) of children continued to have fine motor deficits from 18 months to 5 years. The proportion of infants with gross motor deficits significantly increased over this period (14%, 33% and 81%, p<0.001), particularly for the 'micropreemies' (born <750 g). In multivariate analyses, gross motor development was positively influenced by the quality of the home environment.

CONCLUSIONS

A large proportion of high-risk infants continued to have fine motor deficits, reflecting an underlying problem with fine motor skills. The proportion of infants with gross motor deficits significantly increased, as test demands became more challenging. In addition, the development of gross and fine motor skills appears to be influenced differently by the home environment.

Cost-effectiveness of prophylactic indomethacin in very-low-birth-weight infants

OBJECTIVE

To perform cost-effectiveness analysis to facilitate the decision-making process surrounding use of indomethacin in preterm infants to lower the incidence of patent ductus arteriosus (PDA), intraventricular hemorrhage (IVH), and death.

METHODS

A MEDLINE literature search from 1966 to July 2000 was performed to identify relevant randomized, controlled trials (RCTs), as well as cohort and retrospective case-control studies. A decision tree was built representing the choice to use or not use indomethacin, and the potential outcome costs. Probabilities of being in each chance node were obtained from this search. Where data probabilities were not clear, a sensitivity analysis was conducted.

RESULTS

There was no difference in the expected survival per year; however, there was a significant difference when effectiveness was measured as quality-adjusted life years (QALYs), resulting in 11 and 10 years for the indomethacin and control groups, respectively. The indomethacin treatment cost was $95,157 and that of the control groups was $99,955. The cost effectiveness per life expectancy of being in the indomethacin and control groups was $7142 and $7727, respectively. The sensitivity analysis for PDA closure and prevention of IVH for infants eventually developing PDA versus those without PDA showed no difference. The cost-effectiveness analysis per QALY was $8443 for the indomethacin treatment and $9168 for the control group.

CONCLUSIONS

The prophylactic use of indomethacin is less costly and more effective within an important range of certainty. However, this analysis does not include several potentially confounding factors, such as antenatal steroid use or indomethacin-induced renal toxicity. Depending on the frequency with which these factors arise, economic projections may be considerably altered against the early use of indomethacin.

Favourable neurological outcomes following delivery room cardiopulmonary resuscitation of infants < or = 750 g at birth

OBJECTIVE

To study short- and long-term outcomes of infants < or = 750 g birthweight who received cardiopulmonary resuscitation (CPR) in the delivery room.

METHODOLOGY

A retrospective analysis of all inborn live births < or = 750 g birthweight from 1990 to 1996. Cardiopulmonary resuscitation was defined as positive pressure ventilation via an endotracheal tube and chest compressions. Univeriate analysis were conducted comparing patients according to the use of CPR or positive pressure ventilation alone.

RESULTS

Cardiopulmonary resuscitation was administered to 16 infants: four received chest compressions only and 12 also received adrenaline. Cardiopulmonary resuscitation recipients had significantly lower Apgar scores at both 1 and 5 min, and had delayed onset of spontaneous respiration (P < 0.01). Seven patients died, and eight of nine survivors were free of major neurodevelopmental abnormalities at follow up. All CPR recipients with a 5 min Apgar score of < or = 5 and delayed onset of spontaneous respiration beyond 5 min had poor outcomes.

CONCLUSION

Contrary to the majority of published evidence, delivery room CPR in our extremely small infants was not associated with a high risk of severe neurodevelopmental disability.

Survival and developmental disability in infants with birth weights of 501 to 800 grams, born between 1979 and 1994

OBJECTIVE

Because the survival rate has increased for extremely low birth weight neonates, many have raised the concern that the rate of developmental disability among survivors will also increase. To address this concern, we analyzed changes over time in survival and major neurosensory impairment in a sample of extremely low birth weight infants born between July 1, 1979, and June 30, 1994.

METHODS

The study sample included 513 infants with birth weights of 501 to 800 g who were cared for in either of the two neonatal intensive care units that serve a 17-county region in northwest North Carolina and who were born to mothers residing in that region. At 1 year of age (corrected for gestation), survivors were examined by a pediatrician and were tested using the Bayley Scales of Infant Development. Major neurosensory impairment was defined as cerebral palsy, a Bayley Mental Developmental Index <68, or blindness. A total of 209/216 (97%) of survivors were examined at 1 year of age. Epoch of birth was defined as follows: epoch 1, July 1, 1979 to June 30, 1984; epoch 2, July 1, 1984 to June 30, 1989; and epoch 3, July 1, 1989 to June 30, 1994.

RESULTS

Survival rates for epochs 1, 2, and 3 were, respectively, 24/120 (20%), 63/175 (36%), and 129/218 (59%). In contrast, the proportions with a major neurosensory impairment did not increase over time; rates for successive epochs were 6/24 (25%), 17/61 (28%), and 26/124 (21%). Rates of cerebral palsy were 3/24 (13%), 12/61 (20%), and 9/124 (7%); rates of delayed mental development were 4/24 (17%), 12/61 (20%), and 17/124 (14%); and rates of blindness were 2/24 (8%), 0/62, and 5/124 (4%), respectively.

CONCLUSIONS

This analysis suggests that the increasing survival of extremely low birth weight neonates since the late 1970s has not resulted in an increased rate of major developmental problems identifiable at 1 year of age.

Birth weight and physical ability in 5- to 8-yr-old healthy children born prematurely

Recent advances in perinatal care have resulted in increased survival rates of extremely small and immature newborns. This has resulted in some neurodevelopmental impairment. The purpose of this study was to quantitatively evaluate and compare neuromuscular performance in children born prematurely at various levels of subnormal birth weight (BW). Subjects were 5- to 8-yr-old children born prematurely at different levels of subnormal BW (535-1760 g, N = 22, PM), and age-matched controls born at full term (> 2500 g, N = 15, CON). None of the subjects had any clinically defined neuromuscular disabilities. Body mass (BM) of PM was lower than that of CON (18.3 +/- 2.7 vs 21.7 +/- 3.8 kg) with no difference in height or sum of 4 skinfolds. Peak mechanical power output determined with a 15-s modified Wingate Anaerobic Test and corrected for BM was lower (P = 0.07) in PM than in CON (5.11 +/- 1.07 vs 5.94 +/- 1.00 W.kg-1). This was especially noticeable in children born at extremely low BW (ELBW, < 1000 g, 4.49 +/- 1.04 W.kg-1, P < 0.01). Peak power, determined in a force-plate vertical jump, corrected for BM was lower in PM vs CON (25.5 +/- 5.4 vs 30.8 +/- 5.2 W.kg-1, respectively P = 0.01), especially in the ELBW group (20.0 +/- 5.5 W.kg-1). Similarly, the elapsed time between peak velocity and actual jump take-off was longer in PM than in CON (41.2 +/- 9.4 vs 35.8 +/- 5.8 ms, respectively, P = 0.04). No differences were observed in peak force. The results suggest that performance deficiencies of prematurely-born children may be a result of inferior inter-muscular coordination. The precise neuromotor factors responsible for this should be identified by future research.

Neuropsychological and functional outcomes of very low birth weight infants

Advances in perinatal and neonatal management have resulted in a significant increase in the survival of fragile extremely low birth weight (ELBW) infants > 1,000 g at birth. The evaluation and reporting of the outcome of these infants aids in assessing the efficacy of interventions, provides data to aid in policy decisions, and provides critical information for parents and primary care providers. Comprehensive assessment of multiple domains including neurologic/neurosensory, developmental-cognitive, visual perceptual, speech/language, motor, functional skills for daily living, and Kindergarten readiness permit a total view of the child within the context of the family. Survival of VLBW infants < 800 g has steadily improved from 0% (1943 to 1945) to 49% to 70% (1994 to 1995). Rates of cerebral palsy, mental retardation, blindness, and deafness have remained stable in the 1980s and 1990s. There is evidence, however, that the percent of functional limitations may be increasing. A requirement for Special Education Resources among VLBW infants remains high at 44% to 56%. As increasing numbers of infants at the limits of viability survive, the medical community must remain vigilant in its surveillance and advocate both humanistically and scientifically for comprehensive strategies that optimize long-term functional, academic, and family outcomes.

Survival of very low birthweight and very preterm infants in a geographically defined population

OBJECTIVE

To determine in a geographically defined population 1 year survival of infants with a birthweight of less than 1500 g or gestational age less than 32 weeks, and to establish the effect of postnatal age on predicted survival.

DESIGN

Cohort analysis of 72,427 births to Welsh residents in 1993-94. Deaths were identified using the All Wales Perinatal Survey, a population-based surveillance of mortality between 20 weeks of gestation and 1 year of age.

MAIN OUTCOME MEASURES

Birthweight- and gestation-specific infant mortality, and the effect of postnatal age, gender, and multiple pregnancy on predicted survival.

RESULTS

In normally formed infants 1 year survival at 24-25 weeks gestation was 35%, compared to 75% at 27-28 weeks, and 95% at 30-31 weeks. In infants with a birthweight of 500-699 g 1 year survival was 18% compared to 70% at 800-999 g, and 97% at 1300-1499 g. The chances of survival improved markedly with increasing postanatal age; at 24-25 weeks gestation it was 35% at birth, 50% at 12 h. 66% at 7 days and 78% at 4 weeks. Infant mortality was higher in males, but multiple pregnancy had no effect.

CONCLUSIONS

Up-to-date birthweight- and gestation-specific survival rates are essential for predicting the outcome of a newborn infant. The rapid change in the chances of survival with increasing postnatal age emphasises especially the importance of revising the prediction as the infant gets older, particularly during the first few days of life.

Assisted ventilation and survival of extremely low birthweight infants

OBJECTIVE

To determine the incremental consumption of ventilator resources associated with the improving survival rate of extremely low birthweight (ELBW birthweight 500-999g) infants, from the time assisted ventilation was introduced.

METHODOLOGY

Cohort study of ELBW infants born in one tertiary perinatal centre (The Royal Women's Hospital, Melbourne). All ELBW infants born from 1971 to 1993 were included in the study. In hospital survival rates and patient-days of assisted ventilation were the main outcome measures. Discrete eras of relatively stable survival rate and consumption of ventilator resources were identified. These comprised the years 1971-74, 1977-83, 1985-90, and 1992-93. Cost-effectiveness ratios (the incremental consumption of ventilator resources per additional survivor) were calculated between adjacent eras by dividing the increment in the consumption of ventilator resources by the increment in the survival rate.

RESULTS

The survival rates rose progressively between eras (6.2, 33.9, 49.1, 68.8%, respectively, as did the consumption of ventilator resources (0.1, 6.6, 16.2, 24.7 patient-days of assisted ventilation per livebirth, respectively). The cost-effectiveness ratio deteriorated initially, increasing from 23.2 to 63.5 additional patient-days of assisted ventilation per additional survivor, but then improved, falling to 43.1 additional patient-days of assisted ventilation per additional survivor in the last era. These changes were even more marked for those of birthweight 750-999g (20.0, 63.2 to 35.9 additional patient-days of assisted ventilation per additional survivor, respectively). In contrast, the cost-effectiveness ratio was initially worse for those of birthweight 500-749 g, being three-fold higher than for the larger infants, and only improved substantially in the last era (59.8, 58.3 to 44.1 additional patient-days of assisted ventilation per additional survivor, respectively).

CONCLUSIONS

The initial deterioration in cost-effectiveness ratios between successive eras probably reflected the increased availability of resources for assisted ventilation, without any other major advances in perinatal care. The improvement in cost-effectiveness in the last era reflected, in part, the increased use of antenatal steroid therapy and the introduction of exogenous surfactant to neonatal intensive care.

Changing patterns of survival and outcome at 4 years of children who weighted 500-999 g at birth

OBJECTIVE

To evaluate the impact of changing perinatal practices on survival rates and 4 year neurodevelopmental outcome for infants of birthweight 500-999 g.

METHODOLOGY

The study was a tertiary hospital-based prospective cohort study that compared survival, impairment and handicap rates between two eras, July 1977 to December 1982 (era 1) and January 1983 to June 1988 (era 2). All 348 live, inborn infants and 49 outborn infants of birthweight 500-999 g were prospectively enrolled in a study of survival and outcome. Rates of survival, neurodevelopmental impairment and functional handicap at 4 years were compared between eras. Perinatal risk factors for handicap were also compared between eras.

RESULTS

Four year survival rates for inborn infants 500-999 g improved from 32.6% in era 1 to 49.2% in era 2 (OR 2.1, 95% CI 1.26-3.48) but for outborn infants the improvement between 31.8% and 53.6% was not significant. There were significant improvements in survival for inborn infants in birthweights 800-899 g and 900-999 g between study periods. The rates of functional handicap between the first and second eras (mild 10 vs 7%; severe or multiply severe 14 vs 16%) were not significantly different. Although the rate of cerebral palsy increased from 0 to 12% (P < 0.01) other rates of impairment such as blindness 0 vs 3%, deafness 2 vs 2% and developmental delay 12 vs 11% did not change. The chance of a survivor being free of handicap remained unchanged at 78% and 76% for the two eras, respectively. Although the absolute number of intact survivors more than doubled (41 vs 83) so too did the number of severe or multiply severe handicapped survivors (7 vs 17). Multivariate logistic regression analysis for the entire study cohort revealed male gender, multiple birth, prolonged mechanical ventilation and cerebral ventricular dilatation but not birthweight or gestational age to be independently associated with severe or multiply severe handicap.

CONCLUSIONS

The advances in neonatal intensive care for extremely low birthweight infants between July 1977 and December 1982 and January 1983-June 1988 resulted in an increased number of non-disabled survivors but had no impact on incidence of severe disability. The application of prediction of mortality or severe handicap to clinical practice has the potential to reduce the proportion and absolute number of severely handicapped survivors.

Bilateral spastic cerebral palsy--MRI pathology and origin. Analysis from a representative series of 56 cases

MRI of the brain was performed on 56 children with bilateral spastic cerebral palsy (CP) at a mean age of 10.7 years. Specific pathology was found in 91 per cent; periventricular leukomalacia was present in 42 per cent of term- and 87 per cent of preterm-born children. Parasagittal subcorticocortical injury, multicystic encephalomalacia and basal ganglia lesions were identified in 16 per cent, in all but one associated with severe peri-/neonatal events at term or near term. Maldevelopment comprised 9 per cent, all but one found in term-born children. MRI morphology correlated strikingly with outcome. Periventricular leukomalacia was associated with more severe disability in term- than preterm-born children.

Secular changes in the outcomes to eighteen to twenty-four months of age of extremely low birth weight infants, with adjustment for changes in risk factors and severity of illness

OBJECTIVES

To analyze secular changes in the rates of death and of major impaired outcome in surviving outborn infants who weighted < or = 800 gm at birth and were admitted in 1980 to 1989, with adjustment for changes in risk factors and severity of illness around the time of birth; and to identify changes in these factors that might explain changes in outcomes.

DESIGN

Retrospective cohort study with follow-up to a minimum of 18 months of postterm age. After preliminary screening, multivariate models of association between risk/severity of illness factors and outcomes were constructed, validated, and used to adjust outcomes (death and major impairment to 18 to 24 months of age).

SETTING

Regional neonatal intensive care unit for referral of "outborn" infants.

PATIENTS

Two hundred eighty-seven consecutively admitted infants who weighted < or = 800 gm at birth (97% follow-up).

RESULTS

The death rate during the 1980s did not fall significantly (p adjusted for risk factors = 0.115). The major impairment rate fell (odds ratio, 0.24 (95% confidence interval, 0.10, 0.60); p = 0.002, adjusted for delivery route and respiratory failure measures), mainly because of a reduced rate of blindness, not attributable to cryotherapy. The risk factors that improved and were possibly related to the reduced impairment rate were blood pH and glucose concentration, and serum sodium concentration in the first 48 hours of life.

CONCLUSIONS

Despite an increasing selection for referral of less mature and more severely ill outborn babies near the "limit of viability," and despite more aggressive care, the rate of major impairment fell significantly during the 1980s. This trend was enhanced by adjustment for severity of illness. The fall was attributable to a reduced rate of blindness, and was associated with evidence of improved control of physiologic balance after birth.

The cognitive outcome of very preterm infants may be poorer than often reported: an empirical investigation of how methodological issues make a big difference

The effects of relying on outmoded IQ-test norms and the use of arbitrary classifications of developmental delay on estimates of cognitive impairment of very preterm infants (VPI) was evaluated in a prospective population study. Cognitive assessments included the Griffiths test at 5 and 20 months and the Columbia Mental Maturity Scales (CMM) and a vocabulary test (Aktiver Wortschatz Test, AWST) at 56 months of age. Rates of cognitive impairment of 321 very preterm infants (VPI; < 32 weeks gestation or < 1500 g birth weight) were determined according to the published test norms, to scores of a full-term control group (FC n = 321), and to scores from a representative sample of children (NC n = 431) of the same birth cohort. IQ-scores were higher in the FC and NC children than in the original standardisation sample (SS). Using the concurrent test norms (FC, NC) up to 2.4 times more VPI were identified as seriously impaired (<-2 SD) than if the published (outdated) norms were used. Serious developmental delay was underestimated when arbitrary (e.g. DQ < 70) rather than across age comparable definitions (DQ <-2 SD) were used. VPI study drop-outs had mothers with lower educational qualifications and poorer cognitive developmental scores at 5 or 20 months of age. In conclusion, a lack of appropriate control groups and use of arbitrary criteria for judging serious delay leads to large underestimations of cognitive impairment in VPI. Findings from previous uncontrolled studies of VPI need re-interpretation.

Dynamic model for preventing mental retardation in the population: the importance of poverty and deprivation

A dynamic simulation model is used to answer the question, "What is the most effective child health policy initiative for the prevention of mental retardation (MR)?" The impact of medical strategies is contrasted with social interventions to see how they affect the prevalence of MR in the general population. The model is based on data from four U.S. Census and California Vital Statistics reports (1960, 1970, 1980, 1990). An interstate comparison (California and South Carolina) uses 1990 data. The results of the simulations reveal that medical interventions to improve the developmental outcome of low birth weight (LBW) infants did not cause a reduction in the rate of MR in the population after a 24-year trial period. In contrast, reducing the proportion of children living in poverty who are exposed to environmental deprivation significantly decreased (10%) MR at the end of the model's time period. This analysis supports the view that long-term reduction in MR prevalence is attainable by modifying public policies that influence children's development. Effective MR prevention calls for public policy committed to multifaceted health and educational services for both affected parents and their young children.

Developmental outcome in extremely premature infants. Impact of surfactant

Advances in neonatology, particularly surfactant, have enabled us to significantly improve mortality in the extremely low-birth-weight prematurely born infant. The impact on morbidity remains less clear but decidedly optimistic as the preponderance of the data currently available suggests that although we have not improved outcome in this high-risk group of infants, neither have we increased the percentage of infants with significant impairments. But overall morbidity remains high, especially for the smallest and earliest survivors. There is a growing body of research that supports the idea that with modification of the stressful impact of the NICU environment on the physiologically unstable and vulnerable premature infant, we may be able to improve developmental outcome. We are already seeing even very small infants extubated at a younger age and ready for discharge home well before their originally anticipated "due date." Within this setting we have unequalled opportunity to positively impact development by caring for the infants in a supportive environment that integrates parents as primary caretakers who are comfortable and competent at the time of the infant's discharge home. Further research endeavors should be enlightening in this regard.

Long-term outcome of infants born preterm

This chapter outlines some of the many long-term health problems to be expected in surviving preterm children. They have higher rates of sensorineural impairments (such as cerebral palsy, and visual, auditory and intellectual impairments) and sensorineural disabilities from these impairments, than children born at term. In addition, they grow poorly and have higher rates of other health problems, including poorer respiratory health in early childhood. There is little doubt that preterm children contribute disproportionately to the prevalence of health problems in childhood. However, there are still many gaps in our knowledge of the outcome for preterm survivors, particularly regarding outcome in adulthood. Obstetricians and neonatologists working in intensive care, as well as parents, want to know the long-term outcome for preterm children born today, not that of children born a generation ago when fewer preterm children (particularly those of extremely low birthweight) survived. Despite the many problems, the conclusion is that most preterm children are as healthy as term children, suffering only usual childhood illnesses; we feel confident that the majority make, and will continue to make, useful contributions to their families and the societies in which they live.

Extremely low birthweight infants at 3 years: a developmental profile

This study documents the neurodevelopmental outcome at 3 years of 52 of 55 extremely low birthweight (ELBW) survivors (survival rate 49%) born in a tertiary maternity centre from July 1985 through December 1988, and examines more closely the developmental profile of the neurologically normal survivors. At 3 years, 6 (12%) children had severe neurodevelopmental impairment (severe cerebral palsy, blindness, deafness or a General Quotient (GQ) < 70 on the Griffiths Scales), 11 (21%) had mild to moderate impairment and 35 (67%) had no neurosensory impairment and normal development (GQ > or = 85). Significant risk factors for severe impairment were stage 3 or 4 retinopathy of prematurity (odds ratio [OR] 21.5), treatment with postnatal steroids (OR 21), grade III or IV intraventricular haemorrhage (OR 11) and supplemental oxygen at 'term' (OR 6.4). The developmental profile of the 35 neurologically normal children revealed a significant weakness in eye and hand coordination skills and a relative strength in hearing and speech skills. Early recognition of this developmental profile may allow implementation of more appropriate preschool programmes for ELBW children.

Changing survival and impairment rates at 18-24 months in outborn very low-birth-weight infants: 1984-1987 versus 1980-1983

Outcomes at 18-24 months corrected age of very low-birth-weight infants admitted to our Neonatal Intensive Care Unit in 1984-1987 (period 2) were compared with the outcomes of infants admitted in 1980-1983 (period 1) (total 1357 infants). In the 500-750-g birth-weight subgroup, the survival rate increased from 32 to 54% (p = 0.002). Rates of moderate and severe impairment at 18-24 months (neurosensory deficit, or Bayley corrected mental developmental index < or = 68) in this subgroup decreased from 41 to 15% (p = 0.005), and in those without severe impairment, mean mental Bayley scores in periods 1 and 2 were 84 +/- 18 and 90 +/- 16, respectively (p = 0.20). Analysis after exclusion of small-for-gestational-age infants gave similar results. In the small-for-gestational-age infants of birth weight 500-750 g, the survival rate increased but the impairment rate was unchanged between periods. It is concluded that outcomes improved in 1984-1987 compared with 1980-1983 only for infants with birth weight of 500-750 g.

Low birthweight and risk of mild mental retardation by ages 5 and 9 to 11

This prospective analysis assessed the risk of mild mental retardation (MMR) associated with low birthweight (LBW) in the Child Health and Development Studies. Scores of 50-70 on the Raven Progressive Matrices, a relatively culture-free test of cognitive functioning, were used to categorize MMR. At the age of 5, 13.8% of the 195 children with birthweights less than 2500 g (LBW) were MMR, whilst 4.2% of the 2293 children with normal birthweights (> 2955 grams) were MMR. After adjusting for confounders (maternal age, race, education, prenatal alcohol use, maternal conditions, and congenital anomalies), the relative risk of MMR for LBW was 3.4 (95% CI 1.2-5.4). For children aged 9-11, 7.7% of 194 LBW children were MMR, compared with 6.2% of the 2546 with normal birthweights; the adjusted relative risk for LBW was 1.2 (95% CI 0.7-2.0). Although a strong association between LBW and MMR was observed for both blacks and non-blacks at the age of 5, the association between birthweight and MMR was apparent only for blacks in the cohort of children aged 9-11. These findings suggest that race, a marker for environmental factors which were not measured in this study, may modify the LBW and MMR relationship.

Risk factors for early intraventricular hemorrhage in low birth weight infants

Because earlier studies suggested that preterm infants with germinal matrix hemorrhage or intraventricular hemorrhage or both (GMH/IVH) present within the first 12 postnatal hours are at greatest risk for the development of high-grade hemorrhage and neurodevelopmental disability, we examined the risk factors for this insult among 229 neonates of 600 to 1250 gm birth weight in a multicenter study. All had echoencephalography (ECHO) within the first 11 hours and serially for the next 20 days; risk factor data were collected prospectively. Forty-three infants had GMH/IVH within the first 5 to 11 hours (mean age at ECHO 7.7 hours): 18 GMH and 21 grade II, 1 grade III, and 3 grade IV IVH. One hundred eighty-six infants did not have GMH/IVH at a mean age of 7.9 hours. Both groups of infants were similar in birth weight, gestational age, maternal risk factors, cord pH values, and surfactant therapy before ECHO. The group with early IVH had more vertex presentations than the group without early IVH (79% vs 55%, p = 0.043), less maternal tocolytic use (42% vs 60%, p = 0.029), and more vaginal deliveries (67% vs 44%, p = 0.005). In the first 21 days, severe IVH developed in 12 infants with early IVH and in 6 infants without early IVH (p < 0.001). There were more neonatal deaths (16% vs 6%, p = 0.035) and more deaths at any time during the primary hospitalization (23% vs 9%, p = 0.010) among the early IVH group than among the group without early IVH. Multivariate analysis indicated that the mode of delivery, fetal presentation, and birth weight were important and independent prognostic indicators of IVH.

Survivors of extreme prematurity--outcome at 8 years of age

Of 149 infants liveborn in a large maternity hospital in 1980 to 1982 and delivered between 24 and 29 completed weeks of gestation inclusive, 91 (61%) survived; 88 (97%) survivors were assessed at 8 years' corrected age; 77% of children were not disabled; disability was mild in 13%, moderate in 2% and severe in 4% of children. Although survival decreased with decreasing gestation, disability in survivors did not increase. An earlier assessment of the same children at approximately 2 years of age had been unduly pessimistic particularly for those born less than or equal to 26 weeks' gestation. The only other reports in the literature on outcome by gestation have all assessed the children in early childhood, and estimates of severe disability rates from these studies will probably also be too pessimistic. Since the rate of severe disabilities in infants of borderline viability is not much higher than in more mature infants the obstetrician should mainly consider survival chances for the fetus, and not be overly concerned with long-term neurological outcome, when making clinical decisions.