Improvement of outcome for infants of birth weight under 1000 g. The Victorian Infant Collaborative Study Group

The impact of level of neonatal care provision on outcomes for preterm babies born between 27 and 31 weeks of gestation, or with a birth weight between 1000 and 1500 g: a review of the literature

OBJECTIVE

There is evidence that birth and care in a maternity service associated with a neonatal intensive care unit (NICU) is associated with improved survival in preterm babies born at <27 weeks of gestation. We conducted a systematic review to address whether similar gains manifested in babies born between 27+0 and 31+6 weeks (hereafter 27 and 31 weeks) of gestation, or in those with a birth weight between 1000 and 1500 g.

METHODS

We searched Embase, Medline and CINAHL databases for studies comparing outcomes for babies born between 27 and 31 weeks or between 1000 and 1500 g birth weight, based on designation of the neonatal unit where the baby was born or subsequently cared for (NICU vs non-NICU setting). A modified QUIPS (QUality In Prognostic Studies) tool was used to assess quality.

RESULTS

Nine studies compared outcomes for babies born between 27 and 31 weeks of gestation and 11 studies compared outcomes for babies born between 1000 and 1500 g birth weight. Heterogeneity in comparator groups, birth locations, gestational age ranges, timescale for mortality reporting, and description of morbidities facilitated a narrative review as opposed to a meta-analysis.

CONCLUSION

Due to paucity of evidence, significant heterogeneity and potential for bias, we were not able to answer our question-does place of birth or care affect outcomes for babies born between 27 and 31 weeks? This supports the need for large-scale research to investigate place of birth and care for babies born in this gestational age range.

Outcomes of neonates with birth weight⩽500 g: a 20-year experience

OBJECTIVE

Ethical dilemmas continue regarding resuscitation versus comfort care in extremely preterm infants. Counseling parents and making decisions regarding the care of these neonates should be based on reliable, unbiased and representative data drawn from geographically defined populations. We reviewed survival and morbidity data for our population at the edge of viability.

STUDY DESIGN

A retrospective review of our perinatal database was carried out to identify all infants born alive and admitted to the neonatal intensive care unit (NICU) with BW⩽500 g between 1989 and 2009. Data from the initial hospital stay and follow-up at 24 months were collected.

RESULT

Out of 22 672 NICU admissions, 273 were eligible: 212 neonates were reviewed after excluding infants with comfort care. BW ranged from 285 to 500 g (mean 448 g) and gestational age range 22 to 28 weeks (median 24 week). Sixty-one (28.8%) survived until discharge. Only 13.8% males survived compared with 39.2% females (P<0.05). Half (49%) were discharged with home oxygen/monitor. Fifty (82%) patients' charts were available to review at the 24-month follow-up. Thirty-three percent of surviving infants had a normal neurodevelopmental assessment at 24 months. Forty-three percent had weight/head circumference<5th percentile at 24 months.

CONCLUSION

About a third of neonates admitted to NICU with ⩽500 g BW survived, with 33% of those surviving, demonstrating age-appropriate development at a 24-month follow-up visit.

Flash visual evoked potentials at 2-year-old infants with different birth weights

BACKGROUND

Increased prevalence of visual impairments has been reported in preterm populations. However, it remains unclear about the long-term visual electrophysiological outcomes and their association with visual cognitive functions in premature infants. We investigated visual electrophysiological outcome of 2-year-old infants of different birth weights by flash visual evoked potentials (FVEPs) in order to explore the correlation between visual cognitive functions and FVEPs and to assess the application of FVEPs in evaluating the visual capability of an infant.

METHODS

The FVEPs of 77 infants, including 25 very low birth weight (VLBW) premature infants, 16 low birth weight (LBW) premature infants and 36 full-term infants, were tested with a visual electrophysiological testing device. Neuromotor development was assessed with the Bayley Scales of Infant Development, Second Edition (BSID-II). The visual cognitive functions were evaluated by scoring the proportion passed of 12 items chosen from the BSID-II for infants at 23 to 25 months of age.

RESULTS

The second prominent positive wave (P2) was the major component presented in all three groups. The mean latency of P2 in the VLBW, LBW and full-term groups was 149.65+/-23.79 ms, 129.39+/-8.70 ms, and 126.14+/-7.73 ms respectively. There was no significant difference in mean latency of P2 wave between the LBW and full-term groups; the mean latency of the P2 wave in the VLBW group was delayed more significantly than those of the other two groups. The difference in amplitude of the P2 peak to the preceding N2 peak (N2P2) between the three groups was not statistically significant. The latency of the P2 main wave was negatively correlated with mental developmental index (MDI) (r'(MDI) = -0.35) and visual cognitive capability (r'(visual capability) = -0.21).

CONCLUSIONS

The latency of the P2 main wave on FVEPs was delayed more significantly in premature infants than in full-term infants at 2 years of corrected age. The visual functional development was delayed in premature infants, especially in VLBW infants (gestational age <32 weeks). The FVEPs were reported low but there were statistically significant correlations between measures of visual cognition and P2 peak latency. As a noninvasive and convenient method, FVEPs are useful in assessing certain aspects of an infant's visual development and visual function.

Neurosensory disabilities at school age in geographic cohorts of extremely low birth weight children born between the 1970s and the 1990s

OBJECTIVE

To contrast the rates of neurosensory disabilities at age 8 years in extremely low birth weight (ELBW; birth weight 500 to 999 g) children born in the state of Victoria, Australia in 4 four distinct eras from the late 1970s to the late 1990s.

STUDY DESIGN

Study subjects were assessed at age 8 years. Results were compared among 4 ELBW cohorts (87 of 89 children born in 1979-1980, 206 of 212 born in 1985-1987, 224 of 241 born in 1991-1992, and 160 of 170 born in 1997), and between each of these ELBW cohorts and normal birth weight (NBW; birth weight > 2499 g) controls.

RESULTS

The survival rate for ELBW children rose from 25% for the 1979-1980 cohort to 73% for the 1997 cohort. No statistically significant differences in the disability rates were seen in the 4 eras; however, in the 1997 cohort, disability rates were significantly higher in the ELBW children compared with NBW controls: mild disability, 36.7% vs 9.8%; moderate disability, 10.1% vs 2.3%; and severe disability, 8.2% vs 0.6%.

CONCLUSIONS

The survival rate of ELBW children continues to rise over time. Despite this, however, the rates of disability in these vulnerable children at school age have remained stable and high relative to controls.

Developmental outcomes at the age of two years for very premature babies managed with nasal prong continuous positive airway pressure

AIMS

To describe the developmental progress of very premature babies at the age of 2 years, who were managed in an era where nasal prong continuous positive airway pressure (CPAP) was the preferred method for the management of initial respiratory disease.

METHODS

Two groups of very premature babies of <32 weeks gestation were compared, the first being managed with an intubation and mandatory ventilation approach, and the second being managed with a CPAP approach. The groups are compared with regard to the presence of brain injury, retinopathy and requiring discharge home on oxygen and then at 2 years, for language impairment, non-ambulatory cerebral palsy and significant developmental delay. The study is designed as an audit of data collected prospectively and longitudinally for babies born from 1998 to 2002.

RESULTS

A significant number of babies were successfully managed on CPAP in the second era and significantly fewer received post-natal steroids. The number being discharged home on oxygen, brain injury and retinopathy were similar in the two groups. Developmental outcome assessed at 2 years of age was the same in both eras.

CONCLUSIONS

A CPAP approach to the management of initial respiratory disease in premature babies of less than 32 weeks gestation at birth is associated with no measurable developmental advantage or disadvantage at 2 years of age.

Neonatology fellowship training in research pertaining to development and follow-up

The methodology of the study of the short- and long-term outcomes has changed over the 30-40 years since the indroduction of neonatal intensive care. The training of neonatal fellows in research pertaining to development and follow-up currently needs to include study of epidemiology and biostatistics, knowledge concerning normal and abnormal growth and development throughout the life span and clinical skills and/or knowledge concerning the assessment of neurologic and developmental outcomes.

The effects of an early physical therapy intervention for very preterm, very low birth weight infants: a randomized controlled clinical trial

PURPOSE

A randomized controlled clinical trial was used to investigate effects of physical therapy (PT) intervention on motor outcome of infants born very preterm with very low birth weight (VLBW).

METHODS

Seventy-two infants born very preterm with VLBW were randomly assigned to a nontreatment (NT) (n = 38) or treatment (T) (n = 34) group. The T group received developmental PT from birth until four months corrected age (CA) weekdays during the infant's neonatal stay and on a needs- and problem-orientated basis thereafter. The NT group received no intervention. Both groups were assessed at four months CA using the Alberta Infant Motor Scale (AIMS) as was a control group of 14 infants born full term. Parental compliance was measured using a parent questionnaire.

RESULTS

PT intervention had no significant effect on the T group's motor performance. However, no T group subjects had abnormal motor development at four months CA when compared to the NT group (16%) and the control group (14%) (p = 0.09). The T group subjects with high levels of parental compliance had better scores on the AIMS than those with lower parental compliance (p = 0.05).

CONCLUSION

PT intervention does not significantly affect motor performance of infants born very preterm with VLBW at four months CA. Parental compliance and intervention frequency may have influenced the outcome. Preliminary evidence suggests that neonatal and early PT may reduce the incidence of motor delay among infants born very preterm with VLBW. Follow-up of this group is recommended to ascertain the long-term benefits of this type of early PT.

Regionalized long-term follow-up

The importance of population-based long-term follow-up studies of geographically determined cohorts to evaluate the effectiveness, efficiency and availability of a regionalized perinatal-neonatal care programme is demonstrated by the Victorian Infant Collaborative Study Group. The survival and quality of survival of consecutively born extremely-low-birthweight infants below 1000 g or extremely preterm infants below 28 weeks' gestation in the state of Victoria were assessed up to 14 years of age over four distinctive eras: 1979-1989, 1985-1987, 1991-1992 and 1997. Both survival and quality-adjusted survival rates rose progressively in all birth weight and gestation subgroups, associated with progressively more such infants being born in level III perinatal centres. Cost-effectiveness and cost-utility ratios remained stable overall, with efficiency gains in the smaller infants over time. Regionalized long-term follow-up provides unique information that is not available from institution-based studies, which is vital to the regional organization of perinatal-neonatal care.

Patterns of motor disability in very preterm children

Motor development in very preterm children differs in several important ways from that of children born at full term. Variability is common, although the anatomic and physiologic bases for that variability are often poorly understood. Motor patterns over the first postnatal year may depend on behaviours learned during often long periods of neonatal intensive care. The normal pattern of development may be modified by disturbances of brain function caused both by the interruption of normal brain maturation ex-utero and the superimposition of focal brain injuries following very preterm birth. Abnormal patterns of development over the first year may evolve into clear neuromotor patterns of cerebral palsy or resolve, as "transient dystonias." Cerebral palsy is associated with identified patterns of brain injury secondary to ischaemic or haemorrhagic lesions, perhaps modified by activation of inflammatory cytokines. Cerebral palsy rates have not fallen as might be expected over the past 10 years as survival has improved, perhaps because of increasing survival at low gestations, which is associated with the highest prevalence of cerebral palsy. Children who escape cerebral palsy are also at risk of motor impairments during the school years. The relationship of these impairments to perinatal factors or to neurological progress over the first postnatal year is debated. Neuromotor abnormalities are the most frequent of the "hidden disabilities" among ex-preterm children and are thus frequently associated with poorer cognitive ability and attention deficit disorders. Interventions to prevent cerebral palsy or to reduce these late disabilities in very preterm children are needed.

Temporal and demographic trends in cerebral palsy--fact and fiction

The rate of cerebral palsy has not decreased in developed countries over the past 30 years, despite the widespread use of electronic fetal heart rate monitoring and a 5-fold increase in the cesarean delivery rate over the same period of time. However, neonatal survival has improved during these decades. These observations have lead to the hypothesis that increased survival of premature, neurologically impaired infants may have masked an actual reduction in cerebral palsy among term infants as a result of the use of electronic monitoring and the avoidance of intrapartum asphyxia. A review of the medical literature, as well as a demographic analysis of term and preterm birth rates in the United States, refutes this hypothesis on four grounds. First, cerebral palsy prevalence has been separately analyzed in term infants and shows no change over 30 years. Second, the prevalence of cerebral palsy is the same or lower in underdeveloped countries than in developed nations; in the former, the availability of emergency cesarean delivery based on electronic monitor data is limited or absent. Third, the increase in prevalence of cerebral palsy among low-birth-weight infants and the increase in cesarean sections based on presumed fetal distress were not simultaneous events-the former preceded the latter by a decade. Improved neonatal survival since the 1980s has been associated with a stable or decreasing rate of neurologic impairment and thus could not have obscured improvement from reduced term asphyxia. Finally, compared with the number of infants born by cesarean section for fetal distress, there are simply not enough infants born in the most vulnerable weight groups to make any impact on even a minimal improvement of outcome in the group delivered by cesarean section for presumed fetal distress. Except in rare instances, cerebral palsy is a developmental event that is unpreventable given our current state of technology.

Neuromotor behavioural assessment of preterm infants at risk for impaired development

This study was undertaken to evaluate the effectiveness of a new neuromotor behavioural assessment in identifying preterm infants whose development was potentially at risk as a result of their early birth and immediate postnatal experiences. All infants born at less than 30 weeks gestation or who weighed less than 1000g at birth and cared for in the Mater Hospital's Neonatal Intensive Care Unit in Brisbane over a two year period were included in the study. Infants were assessed in their third week of life and again at 36 weeks gestational equivalent age, or prior to discharge, whichever occurred sooner. Results indicate that the assessment is effective in differentiating those infants who suffered from adverse neonatal events from those who did not, when assessed between 30 and 36 weeks gestational equivalent age. The assessment did not prove useful for infants of less than 30 or greater than 36 weeks gestational equivalent age.

A national short-term follow-Up study of extremely low birth weight infants born in Finland in 1996-1997

OBJECTIVES

The aims of this prospective nationwide investigation were to establish the birth rate, mortality, and morbidity of extremely low birth weight (ELBW) infants in Finland in 1996-1997, and to analyze risk factors associated with poor outcome.

PARTICIPANTS AND METHODS

The study population included all stillborn and live-born ELBW infants (birth weight: <1000 g; gestational age: at least 22 gestational weeks [GWs]), born in Finland between January 1, 1996 and December 31, 1997. Surviving infants were followed until discharge or to the age corresponding with 40 GWs. National ELBW infant register data with 101 prenatal and postnatal variables were used to calculate the mortality and morbidity rates. A total of 32 variables were included in risk factor analysis. The risk factors for death and intraventricular hemorrhage (IVH) of the live-born infants as well as for retinopathy of prematurity (ROP) and oxygen dependency of the surviving infants were analyzed using logistic regression models.

RESULTS

A total of 529 ELBW infants (.4% of all newborn infants) were born during the 2-year study. The perinatal mortality of ELBW infants was 55% and accounted for 39% of all perinatal deaths. Of all ELBW infants, 34% were stillborn, 21% died on days 0 through 6, and 3% on days 7 though 28. Neonatal mortality was 38% and postneonatal mortality was 2%. Of the infants who were alive at the age of 4 days, 88% survived. In infants surviving >12 hours, the overall incidence of respiratory distress syndrome (RDS) was 76%; of blood culture-positive septicemia, 22%; of IVH grades II through IV, 20%; and of necrotizing enterocolitis (NEC) with bowel perforation, 9%. The rate of IVH grades II through IV and NEC with bowel perforation decreased with increasing gestational age, but the incidence of RDS did not differ significantly between GWs 24 to 29. A total of 5 infants (2%) needed a shunt operation because of posthemorrhagic ventricular dilatation. Two hundred eleven ELBW infants (40% of all and 60% of live-born infants) survived until discharge or to the age corresponding with 40 GWs. The oxygen dependency rate at the age corresponding to 36 GWs was 39%, and 9% had ROP stage III-V. Neurological status was considered completely normal in 74% of the surviving infants. The proportions of infants born at 22 to 23, 24 to 25, 26 to 27, and 28 to 29 GWs with at least one disability (ROP, oxygen dependency, or abnormal neurological status) at the age corresponding to 36 GWs were 100%, 62%, 51%, and 45%, respectively. Birth weight <600 g and gestational age <25 GWs were the independent risks for death and short-term disability. The primary risk factor for IVH grades II through IV was RDS. Low 5-minute Apgar scores predicted poor prognosis, ie, death or IVH, and antenatal steroid treatment to mothers with threatening premature labor seemed to protect infants against these. Some differences were found in the mortality rates between the 5 university hospital districts: neonatal mortality was significantly lower (25% vs 44%) in one university hospital area and notably higher (53% vs 34%) in another area. Furthermore, significant differences were also found in morbidity, ie, oxygen dependency and ROP rates. Differences in perinatal (79% vs 45%) and neonatal (59% vs 32%) mortality rates were found between secondary and tertiary level hospitals.

CONCLUSION

Our study shows that even with modern perinatal technology and care, intrauterine and early deaths of ELBW infants are common. The outcome of infants born at 22 to 23 GWs was unfavorable, but the prognosis improved rapidly with increasing maturity. The clear regional and hospital level differences detected in survival rates and in short-term outcome of ELBW infants emphasizes that the mortality and morbidity rates should be continuously followed and that differences should be evaluated in perinatal audit procedures. (ABSTRACT TRUNCATED)

Growth and respiratory health in adolescence of the extremely low-birth weight survivor

ELBW children grow poorly in early childhood, but catch up substantially in weight and height by 14 years of age. The final adult stature for ELBW children remains to be determined. Despite the need sometimes for prolonged periods of assisted ventilation and oxygen therapy, the respiratory health and lung function of ELBW children is mostly normal in adolescence. ELBW children with BPD had similar respiratory health compared with ELBW children without BPD. The effects of cigarette smoke, both passive and active, and of newer therapies, such as exogenous surfactant and postnatal corticosteroids, on respiratory health in adulthood remain to be determined.

Racial differences in temporal changes in newborn viability and survival by gestational age

This study examines trends in the rates of very preterm, moderately preterm and gestational age-specific neonatal mortality, and in the gestational age limit of viability in South Carolina (SC) from 1975 to 1994. We also investigate whether trends were similar between African-Americans and Whites. We hypothesised that disproportionate reductions in gestational age-specific mortality, rather than any major changes in the gestational age distributions of either race group, underlie any increasing racial disparity in overall mortality rates. During 1975-94, single livebirths, who were born to mothers resident in SC and were either White or African-American based on recorded maternal race, were selected for the investigation. We define the gestational age limit of viability as the gestational age at which > or = 50% of infants in the population died within 28 days of life. Although preterm percentages have not improved, there was a marked decline in neonatal mortality. Gestational age-specific neonatal mortality decreased for both race groups, although there were greater reductions for White preterm infants. By the end of the study period, the African-American neonatal mortality rate was 2.3 times that of Whites and the gestational age at which 50% of newborns died within 28 days of life was 24.5 weeks for Whites and 23.9 weeks for African-Americans. The ongoing decline in neonatal mortality continues to be mainly due to reductions in gestational age-specific neonatal mortality, probably related to high-risk obstetric and neonatal care. Technological developments in these areas may have differentially benefited Whites, resulting in an increasing racial disparity in neonatal mortality rates. Preterm African-American infants no longer have a marked survival advantage over White infants, even at the gestational age limit of viability.

Trends and racial differences in birth weight and related survival

OBJECTIVE

In the past two decades, infant mortality rates in the United States declined in African-American and White populations. Despite this, racial disparities in infant mortality rates have increased and rates of low birth weight deliveries have shown little change. In this study, we examine temporal changes in birth weight distributions, birth weight specific neonatal mortality, and the birth weight threshold for an adverse risk of survival within both racial groups in order to explore the mechanisms for the disparities in infant mortality rates.

METHOD

Single live births born to South Carolina resident mothers between 1975 and 1994 and considered White or African-American based on the mother's report of maternal race on the birth certificate were selected for investigation. We define the birth weight threshold for adverse survival odds as the birth weight at which 50% or more of infants in the population died within the first month of life.

RESULTS

Despite significant increases in very low birth weight percentages, neonatal mortality rates markedly declined. Birth weight specific neonatal mortality decreased for both races, although greater reductions accrued to White low birth weight infants. By the end of the study period, the birth weight at which over 50% of newborns died within the first month of life was 696 g for Whites and 673 g for African-Americans.

DISCUSSION

The ongoing decline in neonatal mortality is mainly due to reductions in birth weight specific neonatal mortality, probably related to high-risk obstetric and neonatal care. Technological developments in these areas may have differentially benefited Whites, resulting in an increasing racial disparity in mortality rates. Moreover, the relatively greater and increasing mortality risk from postmaturity and macrosomia in infants of African-America mothers may further exacerbate the racial gap in infant mortality.

Neurodevelopment until the adjusted age of 2 years in extremely low birth weight infants after early intervention--a case-control study

A total of 104 infants with birth weights of less than 1000 grams were enrolled in this prospective case-control study in order to examine the effect of occupational therapy based on sensory integration (SI) and neurodevelopmental therapy (NDT) on neurological development. The children were grouped as matched pairs on the basis of a set of developmental risks assessed at the age of 3 months. The intervention children had a weekly session of 60 minutes of occupational therapy from the corrected age of 6 months up to 12 months. All the children were examined at the corrected age of 3, 6, 9, 12, 18 and 24 months. The neurodevelopment of the cases and the controls did not differ essentially and the only significant difference was found in the social development of the children at the age of 12 months to the advantage of the intervention group. It is concluded that this amount of occupational therapy in at-risk children does not have a relevant effect on neurological development.

Chronic physiologic instability is associated with neurodevelopmental morbidity at one and two years in extremely premature infants

OBJECTIVE

The objective of this study was to evaluate the relationships between chronic physiologic instability, as assessed by the cumulative daily Score for Neonatal Acute Physiology (SNAP), and neurodevelopmental morbidity in premature infants at 1 year and at 2 to 3 years of age.

DESIGN

The subjects of this retrospective study were extremely premature (</=30 weeks' gestational age [GA]) infants born in 1993 and 1994 who were seen in follow-up at least once between 1 and 3 years of age. Cumulative daily SNAP scores were calculated over the entire neonatal intensive care unit course for 96 infants (mean GA, 27.3 +/- 1.6 weeks; mean birth weight, 1065 +/- 270 g). The Mental and Psychomotor Developmental (MDI and PDI) of the Bayley Scales of Infant Development (II) were administered at 1 year and at 2 to 3 years of age; the Receptive-Expressive Emergent Language Scale (REEL) was administered at 2 to 3 years of age. To compare the most stable infants with the most unstable infants, the subjects were divided into three quartile groups based on their cumulative SNAP scores (<25th percentile, 25 to 75th percentile, and >75th percentile). MDI, PDI, and REEL scores were compared for the three groups using analysis of variance. To evaluate the relative contributions of physiologic stability, intracranial abnormalities, GA, and early postnatal nutritional intakes, multiple regression analyses were performed using cumulative SNAP score, an intraventricular hemorrhage (IVH) score (incorporating IVH and periventricular leukomalacia), GA, and a weight-change score for the first month as independent variables, and MDI, PDI, and REEL quotients as dependent variables. Regression analyses were repeated, with cumulative SNAP subscores for oxygenation, hypotension, acidosis, and hypoxia/ischemia included with IVH score, GA, and first month weight z score change as independent variables, and MDI, PDI, and REEL quotients as dependent variables.

RESULTS

The infants with the highest degree of physiologic instability (cumulative SNAP scores greater than the 75th percentile) had significantly lower MDI scores at 1 year of age and lower PDI scores at 1 year and at 2 to 3 years of age than did infants who were more physiologically stable. Sixty-seven percent of infants with cumulative SNAP scores greater than the 75th percentile had neurodevelopmental abnormalities at 2 to 3 years of age (cerebral palsy or delayed mental, motor, or language development). Using multiple regression analyses, higher cumulative SNAP scores, IVH scores, and GA were associated with lower 1-year MDI scores. Higher cumulative SNAP scores and IVH scores were associated with lower 1-year PDI scores. By 2 years, only higher cumulative SNAP scores were significantly associated with lower MDI and PDI scores. With respect to language development, only lower weight-change scores over the first month were significantly associated with poorer receptive language development. Lower weight-change scores over the first month and higher hypotension scores were significantly associated with poorer expressive language development. In the secondary regression analyses, higher IVH score, higher cumulative oxygenation scores, and higher hypoxia/ischemia scores all were significantly associated with lower 1-year MDI scores. By 2 to 3 years of age, only higher oxygenation scores were significantly associated with lower MDI scores.

CONCLUSIONS

Prolonged physiologic instability was associated with deleterious neurodevelopmental consequences for extremely premature infants through 2 to 3 years of age, independent of effects of intracranial abnormalities and GA.

Preterm infants 30-36 weeks' gestation in Victoria--where should they be delivered?

There is little doubt that very preterm infants <30 weeks' gestation should be born in level-3 perinatal centres. For preterm infants 30-36 weeks' gestation, however, the optimum place of birth is not so clear-cut. The aims of this study of livebirths 30-36 weeks' gestational age born in Victoria were to determine: 1) the proportions delivered outside level-3 centres, and 2) for infants born outside level-3 centres, the proportions transferred after birth to a level-3 nursery in the first days after birth. Data on the number of livebirths 30-36 weeks' gestational age in Victoria in the 3 years 1994-1996, inclusive, were supplied by the Victorian Perinatal Data Collection Unit. Data were obtained from the Newborn Emergency Transport Service (NETS) on all transfers within the first 3 days after birth to a level-3 centre for infants born outside level-3 centres. For the 3 years 1994-1996 there were 11,375 livebirths 30-36 weeks' gestational age in Victoria. The proportion born outside a level-3 perinatal unit was 57.9% overall, and rose with increasing gestational age, from 10.9% at 30 weeks to 69.0% at 36 weeks. Of the 6,587 livebirths outside a level-3 centre, 808 (12.3%) were transferred within the first 3 days after birth by NETS to a level-3 centre, the proportions falling with increasing maturity, being 73.7%, 48.5%, 28.4%, 26.9%, 18.8%, 11.8%, and 7.0% at 30, 31, 32, 33, 34, 35, and 36 weeks, respectively. These data may help medical practitioners when determining the place of delivery for infants 30-36 weeks' gestation.

Ocular sequelae in extremely premature infants at 5 years of age

OBJECTIVE

To report long-term ophthalmological sequelae in extremely premature infants at 5 years and to determine the relationship between neonatal variables (including retinopathy of prematurity; ROP) and the 5 year ophthalmological outcome of these infants.

METHODOLOGY

The study cohort comprised 84 surviving infants born with a birthweight < 1000 g or gestational age < 28 weeks from June 1985 to December 1989. All infants had an ophthalmological assessment between 34 and 40 weeks post conceptional age to document grade of ROP and were assessed at 5 years of age for fundoscopy, visual acuity, refractive error and ocular mobility.

RESULTS

Of the 84 long-term survivors 69 (82%) were formally assessed at 5 years. Overall, 30 (43%) had some form of ocular disorder. Nineteen (27%) had reduced visual acuity of < 6/6 and three of these were blind. Myopia > -0.5 dioptre was noted in eight (12%), hypermetropia > or = 2.0 dioptre in five (8%), astigmatism in seven (11%) and strabismus was present in nine (14%) of the cohort. There was a significant relationship (P < 0.0001) between the incidence of ocular disorders and ROP. However, even those premature children without ROP had a 31% incidence of ocular disorder at 5 years.

CONCLUSION

Long-term ophthalmological follow-up is recommended in all extremely premature infants regardless of the presence of ROP in the neonatal period.

Survival and neonatal and neurodevelopmental outcome of 24-29 week gestation infants according to primary cause of preterm delivery

A total of 189 infants of 24-29 weeks' gestation were born in a regional perinatal centre during a 2-year period. They were divided into groups according to the primary cause of preterm delivery: antepartum haemorrhage (n = 37, 20%), preeclampsia (n = 27), 14%), preterm premature rupture of membranes (n = 64, 34%), preterm labour (n = 27, 14%), chorioamnionitis (n = 16, 8%), other complications (n = 18, 10%). The perinatal mortality rate (PMR) was 286/1,000 of whom 44% were stillbirths. The 'other complication' group had the highest PMR due to a large number of intrauterine deaths, with no differences in neonatal mortality between the groups. Preeclampsia was associated with an increased risk of necrotizing enterocolitis and chorioamnionitis was associated with an increased risk of periventricular haemorrhage. Follow-up to at least 2 years was performed in 122 (97%) of survivors. Cerebral palsy occurred in 7%, while 18% had neurodevelopmental disability. No relationship was found between primary cause of preterm delivery and outcome. This information should be of value in counselling parents when preterm delivery is imminent.

Evaluation of neurodevelopmental outcome in high-risk infants in Australia

An understanding of the neurodevelopmental outcome of long-term survivors of neonatal intensive care is essential for the informed management of preterm or high risk infants. This annotation looks at the current status of neonatal follow-up services in Australasia and highlights problems in the collection and interpretation of data. It suggests that we should work towards achieving a consensus on standard definitions and test regimes and on national data collection.

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.

Intelligence and Learning Disabilities in 6- to 8-year-old Children Weighing under 1000 Grams at Birth

Intellectual ability and learning disabilities (LD) were assessed in a cohort of 33 extremely low-birthweight (1000 grams) children at 6-8 years of age with a psychometric test battery. The children were classified into the following three groups: a LD-suspected group of 9 boys (27.3%), a mentally delayed group of 3 boys and 3 girls (18.2%), and a typically developing group of 6 boys and 11 girls (51.5%). No correlation was found between birthweight and intelligence quotient (IQ) at 6-8 years of age. A negative correlation was found between IQ and gestational age (GA) at a nearly significant level. The mean verbal IQ for the 11 small for gestational age (SGA) children was significantly lower than that of the appropriate for gestational age (AGA) children. The LD-suspected group was characterised by lower scores on spatial relationships and rapid but inaccurate solving of the visuo-motor integration tasks on the Frostig test.

Prevalence and aetiology of neurological impairment in extremely low birthweight infants

OBJECTIVE

To determine the prevalence and perinatal predictors of cerebral palsy, intellectual impairment, visual impairment and deafness in a cohort of extremely low birthweight (ELBW) infants at two years of age.

METHODOLOGY

The study population comprised 199 of the 224 (89%) ELBW infants managed at the Mater's Mothers Hospital, Brisbane, between July 1977 and February 1990 and who survived to two years. The prevalence of cerebral palsy, intellectual impairment, blindness and deafness was measured by clinical,psychometric and audiological assessment and the association with 24 risk factors examined.

RESULTS

Cerebral palsy occurred in 20 children (10%). Risk of cerebral palsy was associated with ventricular dilatation, intraventricular haemorrhage, necrotizing enterocolitis and multiple birth, though only ventricular dilatation (OR 4.41; 95% CI 1.32-14.8) remained significant in the adjusted analysis. Intellectual impairment occurred in 20 children (10%) and was independently associated with ventricular dilatation (OR 15.0; 95% CI 2.2-102.8), ventilation F(i)(2) > 80% (OR 3.4; 95% CI 1.01-11.5), vaginal delivery (OR 3.5; 95% Cl 1.09-11.4) and male sex (OR 6.1; 95% Cl 1.67-22.3). No perinatal predictor was statistically associated with risk of deafness. Retinopathy of prematurity (OR 36.9; 95% Cl 2.8-495.5) was associated with risk of later visual impairment.

CONCLUSIONS

Intellectual impairment was associated with a broad range of perinatal variables. Cerebral palsy was associated with fewer variables, all of which were also associated with intellectual impairment. Neurologic injury was associated with male sex and multiple birth, which are not biological insults themselves, but may be markers of susceptibility to injury.

Surgery and the tiny baby: sensorineural outcome at 5 years of age. The Victorian Infant Collaborative Study Group

OBJECTIVE

To determine whether an association exists between long-term sensorineural outcome and the need for surgery requiring general anaesthesia during the primary hospitalization in extremely preterm (<27 weeks of gestational age) or extremely low birthweight (ELBW birthweight <100Og) infants.

METHODOLOGY

A geographically determined cohort study of extremely preterm or ELBW children in the State of Victoria, Australia. The study subjects were consecutive survivors with either gestational ages <27 weeks or birthweights <10OOg born in the State of Victoria during 3 years from 1 January 1985. The main outcome measure was the rate of sensorineural disability at 5 or more years of age in relation to surgical procedures requiring general anaesthesia performed during the primary hospitalization.

RESULTS

Of 221 children surviving to 5 years of age, 54 (24.4%) had at least one surgical operation requiring general anaesthesia during their primary hospitalization. The operations included the following: (i) ligation of ductus arteriosus (n = 26); (ii) inguinal hernia repair (n = 16); (iii) central nervous system surgery (n = 4); (iv) gastrointestinal surgery (n = 5); and (v) tracheostomy or bronchoscopy (n = 5). Of the 221 survivors to 5 years of age, 218 (98.6%) were assessed for sensorineural impairments and disabilities. Of the 53 children who were assessed at 5 or more years of age and who had had surgery, 7 (13.2%) were severely disabled, 8 (15.1%) were moderately disabled, 12 (22.6%) were mildly disabled,and 26 (49.1%) were non-disabled. The overall rate of sensorineural disability was significantly higher in children who had been operated on compared with those who had not (Mann-Whitney U-test, z =3.7, P<0.001).

CONCLUSIONS

There is an adverse association between the need for surgery requiring general anaesthesia during the primary hospitalization and sensorineural outcome in extremely preterm or ELBW infants.

Impact of extremely immature infants on neonatal services

The impact of very immature infants on neonatal services was examined within the United Kingdom. The Trent Health Region was used as a geographically defined population. Data were obtained on all infants weighing less than 1501 g at birth and all infants born before 32 weeks gestation between 1991-93. Information relating to length of stay, duration of ventilation, and survival was documented. Only one of 49 infants born before 24 weeks gestation survived. However, 75% of this group were ventilated. Most of the remaining infants died before 48 hours of age. A similar pattern was also seen in infants of 24 and 25 weeks gestation. Infants under 24 weeks gestation comprised 1.5% of all ventilated infants and consumed 2.14% of the total neonatal ventilator days for the region. It is concluded that the United Kingdom operates a conservative policy towards infants born before 24 weeks gestation and as a result resources expended on them are limited.

Neurosensory outcome at 5 years and extremely low birthweight. The Victorian Infant Collaborative Study Group

OBJECTIVE

To establish the stability of neurosensory outcome at 5 years of age compared with 2 years of age, and to determine whether the improving survival rate of extremely low birthweight (ELBW) (500-999 g) children has been accompanied by an increase in the number of severely impaired and disabled children in the community.

METHODS

A geographically determined cohort study was made of consecutive ELBW survivors born in the state of Victoria during 1985-7, and during 1979-80, inclusive. Rates of neurosensory impairments and disabilities at 2 and 5 or more years of age were measured.

RESULTS

Of 212 children surviving to 5 years of age born during 1985-7, 211 (99.5%) had been assessed at 2 years of age, and 209 (98.6%) were assessed at 5 or more years of age. Of the 208 children seen at both 2 and 5 years, 32 children had deteriorated, 23 children had improved, and 153 were unchanged, compared with their 2 year assessment. The major reason for a change in classification was an alteration in psychological test results. Compared with ELBW children born in 1979-80, those born in 1985-7 had significant reductions in hearing and intellectual impairment. The rate of severe neurosensory disability in the 1985-7 cohort was 5.7% compared with 12.4% in children born in 1979-80.

CONCLUSIONS

The age of 2 is too early to be sure of neurosensory outcome in ELBW infants. The additional survivors born in the mid 1980s, compared with the late 1970s, are free of severe neurosensory disability at 5 years of age, with no increase in the absolute number of ELBW children surviving with severe neurosensory disability.

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.

Improving outcome for Western Australian infants with birthweights 500-999 g

OBJECTIVE

To assess changes in survival and disability in liveborn extremely low birthweight infants (500-999 g) in Western Australia, 1980-1987.

DESIGN

Cohort study comparing two periods, 1980-1983 (P1) and 1984-1987 (P2).

PARTICIPANTS

All 586 liveborn extremely low birthweight infants in WA in 1980-1987 (266 in P1, 320 in P2).

MAIN VARIABLES EXAMINED

Birthweight, place of birth, age at death, neurosensory examination findings and scores on the Griffiths Mental Development Scales or other standardised test results.

RESULTS

482/586 infants (82%) were born at King Edward Memorial Hospital (KEMH), a level III referral centre, and a further 4% were transferred there after birth. The proportion born at KEMH increased from 78% in P1 to 86% in P2. Survival increased from 35% to 43% overall. In those below 800 g birthweight, survival doubled from 14% to 29%. There was no change in the age at death for non-survivors. Follow-up information was known for 222 of the 229 survivors at median ages of 46 months (P1) and 43 months (P2). Disability rates in infants below 800 g birthweight remained static (P1, 26%; P2, 28%), but fell in those of 800-999 g birthweight from 24% to 13%. Overall, survival free of disability increased from 26% to 34%.

CONCLUSION

Increased survival rates occurred without any increase in the rate or severity of disability in survivors.

Extremely low birth weight and control infants at 2 years corrected age: a comparison of intellectual abilities, motor performance, growth and health

A 2-year cohort of 63 surviving extremely low birth weight (ELBW) infants was prospectively studied and 60 of these infants, together with 44 normal birth weight control infants, were assessed at 2 years of age for intellectual abilities, motor skills, growth and health. The total ELBW group differed significantly from controls on overall Griffiths developmental quotient (99.3 vs. 103.8 P = 0.02) and in the personal/social subscale (100.7 vs. 106.7 P = 0.01). A subset of 43 of the ELBW infants was identified as low risk at discharge. No statistically significant differences were present between the low risk ELBW subset and controls in intellectual abilities though both the total ELBW group and the low risk ELBW subset differed from controls in fine and gross motor abilities, and in weight at 2 years. The total ELBW group also experienced more frequent ill health and hospital readmission.

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.

A changing pattern of cerebral palsy. Declining trend for incidence of cerebral palsy in the 20-year period 1970-89

In a population-based study cerebral palsy (CP) was diagnosed in 110 cases (2.4 per 1000) among children live born with birth weight > or = 500 g (n = 45,976) during the 20-year-period 1970-89 (CP cases with a postneonatal etiology excluded). The CP-incidence showed a linear trend of decline from 2.8 per 1,000 in the first 5-year-cohort born 1970-74, to 2.0 per 1,000 in children born 1985-89 (p = 0.17). Birth weight specific CP-incidence showed a trend of decline in very low birth weight infants (500-1,499 g) and in infants > or = 2,500 g from the first 10-year-cohort born 1970-79 to the second born 1980-89. The same trend occurred for the incidence of spastic diplegia in total and in children born preterm. These trends of decline did not achieve statistical significance (p > 0.05). The CP-incidence was 36.7 and 11.3 times higher among infants with birth weight 500-1,499 g and 1,500-2,499 g respectively compared to infants > or = 2,500 g (p < 0.01). 15.9% of the decline in CP-incidence from the first to the second 10-year-cohort could be explained by a decreased low birth weight rate (500-2,499 g) in the population, from 4.2% 1970-79 to 3.8% 1980-89 (p < 0.05). The origin of CP was considered prenatal in 22 (20%), perinatal in 47 (42.7%), and undifferentiated in 41 (37.3%) of the cases. More CP-children born in the 10-year-period 1980-89 were treated with mechanical ventilation in the neonatal period (13/46; 28.3%) than those born in the 10-year-period 1970-79 (4/64; 6.3%) (p < 0.01). The neonatal mortality rate declined significantly from 7.2 per 1,000 in the first to 3.9 per 1,000 in the last 10-year-cohort respectively (p < 0.01). Birth weight-specific neonatal mortality rates declined more than 50% in all weight groups (p < 0.01). The results are contradictive to other investigations showing increased CP-incidence following improved survival rates in low birth weight infants, and may reflect a different pattern for development of perinatal care (organization, intensive care). The overall effect of mechanical ventilation may be improved survival and prevention of brain damage, though the percentage of ventilated CP-children increased. Preventing low birth weight should be a main strategy for preventing CP.

Perinatal outcomes of a large cohort of extremely low gestational age infants (twenty-three to twenty-eight completed weeks of gestation)

OBJECTIVES

To determine gestational age (GA)-specific mortality rates; the effects of GA, birth weight, sex, and multiple gestation on mortality rates; short-term morbidity for infants born at 23 to 28 weeks GA; and impairment rates at a corrected chronologic age of 18 months for those born at 23 to 25 weeks GA.

METHODS

A data base analysis was performed with a linked obstetric and a neonatal database. GA was determined by obstetric data and confirmed by early ultrasonography (available in 88%) on all births < 30 weeks GA at British Columbia's tertiary perinatal center from 1983 to 1989.

RESULTS

Of 1024 births occurring between 23 and 28 weeks GA, 911 were live born. The mortality rate decreased with increasing GA: 84% at 23 weeks; 57% at 24 weeks; 45% at 25 weeks; 37% at 26 weeks; 23% at 27 weeks; and 13% at 28 weeks GA. For each GA, mortality rate versus birth weight plots showed a decreasing mortality rate with increasing birth weight, except for infants who were large for GA. Male infants had a higher mortality rate than female infants (odds ratio, 1.8; confidence interval, 1.4 to 2.5). Twins fared worse than singletons with a decreasing effect from 24 weeks GA (odds ratio, 10.3) to no effect at 28 weeks GA. The median number of days supported by mechanical ventilation and the length of stay in the neonatal intensive care unit decreased markedly with increasing GA. Eighteen-month outcome of survivors between 23 and 25 weeks GA with 93% follow-up rate revealed an overall impairment rate of 36%, but 6 of the 9 surviving 23-week infants had major impairments.

CONCLUSIONS

The GA-specific perinatal outcome results of this large cohort provide information to assist in perinatal management decision making and for counseling parents prenatally.

Annual audit of three year outcome in very low birthweight infants

Annual odds ratios, standardised for known confounding variables, were used to examine trends in outcome at 3 years of age among 1499 infants of less than 1500 g birth weight admitted to a regional referral centre between 1980 and 1989. Despite improved survival, the chance of survival with a major disability or with cerebral palsy was unchanged. The likelihood of dying or surviving with a major disability significantly reduced during the decade.

Outcome of infants born preterm, with special emphasis on extremely low birthweight infants

The outcome of extremely low birthweight (ELBW) infants has been reviewed from published articles and up-to-date data from Japan. The mortality rate of these infants declined significantly from over 90% to below 50% after the introduction of intensive care in the 1970s, but the incidence of major neurological sequelae remained steady at around 20%. Similarly, the incidence of major neurological sequelae did not increase along with the decrement of birthweight, although the mortality rate increased significantly. Long-term follow-up of ELBW children until school age has revealed poor school performance in spite of the absence of major neurological sequelae and the attainment of average intelligence quotient scores. Physical growth is retarded initially but generally catches up by the age of 8-9 years. In Japan, the neonatal mortality rate of ELBW infants declined from 56% in 1981 to 25% in 1989 with an increased birth rate of ELBW infants. In ELBW infants cared for at Tokyo Women's Medical College during 1984-90, the survival rate was 112 out of 134 (84%) and the incidence of major neurological sequelae was 15 out of 87 (17%) at 1-8 years old. The viability limit of ELBW infants has been discussed based on recent data. As a result of the rapid progress of medical care of ELBW infants, their viability limit as defined in the Eugenic Protection Law in Japan was amended from 24 completed weeks of gestation to 22 completed weeks in 1991.

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.