Low birth weight, intrauterine growth retardation, and preterm delivery

The relationship between low birth weight, intrauterine growth retardation, and preterm delivery in infants born at a perinatal center is described. Between 20% and 30% of infants born weighing 500 to 2000 gm and nearly 50% of infants born weighing 2001 to 2750 gm had intrauterine growth retardation. For infants within the same low-birth weight group, infants with intrauterine growth retardation had one half to one sixth of the neonatal mortality rate of non-growth-retarded infants. However, only in the 501 to 1000 gm group did the difference in mortality between infants with and without intrauterine growth retardation substantially influence the composition of the group of survivors.     

Breech delivery: evaluation of the method of delivery on perinatal results and maternal morbidity

A retrospective study of 460 single-gestation infants in breech position was conducted at the University of Colorado Medical Center to assess the impact of a policy for the selection of cases for vaginal delivery. Among infants weighing more than 2,500 grams, there was an increase in the cesarean section rate from 13% to 54%, with an associated increase in maternal morbidity from 7% to 15%. This occurred with no significant reduction in adverse perinatal outcome. However, a case-by-case review suggests that more frequent and timely cesarean sections would have further reduced perinatal morbidity and deaths among term infants. Among the infants weighing 2,500 grams or less there was an increase in cesarean births from 5% to 55% following the introduction of the strict criteria for vaginal delivery. Among the infants weighing 1,501 to 2,500 grams there was no significant difference in survival between the cesarean and vaginally delivered patients. Although infants weighing 501 to 1,500 grams delivered by cesarean section survived more frequently than did those delivered vaginally, the differences in perinatal deaths may have been due to a higher birth weight in the cesarean-delivered infants or an over-all improvement in neonatal intensive care for infants of very low birth weight.     

Maternal transport and the perinatal denominator

In conjunction with an active outreach program, a rural perinatal region of 18,000 deliveries was analyzed. All pregnancies which resulted in the delivery of live-born infants weighing 1,000 to 1,500 gm were reviewed for maternal/fetal risk and eventual neonatal outcome. Analysis included all mothers and infants cared for at regional hospitals as well as those transferred to any tertiary care center in the state system. Thus, an entire "perinatal denominator" for this group of patients at very high risk was identified. Maternal/fetal risk scoring was highest for the group of mothers transferred to the tertiary center prior to delivery. In spite of this increased risk, infant mortality was significantly decreased by delivery at the tertiary care center. It is recommended that other groups of high-risk conditions be evaluated in regional systems only after the entire perinatal denominator has been identified.     

Neonatal mortality in infants born weighing 501 to 1000 grams. The influence of changes in birth weight distribution and birth weight-specific mortality rates on neonatal survival

We analyzed changes over time in neonatal mortality rates for infants born weighing 501 to 1000 gm. The decline in total mortality in this weight group due to improved small-group, birth weight-specific mortality was contrasted to the increase in mortality caused by changes in the birth weight distribution resulting from the care of smaller infants. Had the birth weight distribution remained unchanged, the total improvement in neonatal mortality for the entire 501 to 1000 gm group would have been substantially greater.     

Prematurity and the obstetrician. A regional neonatal intensive care nursery is not enough

Modern-day perinatal care has resulted in dramatically improved outcomes of premature infants, particularly those weighing 750 to 1,500 gm or of 27 to 32 weeks' gestational age. Assuming that the birth is not traumatic, the infant asphyxiated, or made hypothermic at birth, the chances of the very small premature baby developing normally are great. The delivery of an infant of less than or equal to 32 weeks' gestational age or weighing less than 1,500 gm should occur at a perinatal center when possible.     

Neonatal survival and perinatal factors in infants born at 24 to 32 weeks of gestation

Clinical associations between neonatal survival and perinatal factors were studied in very premature infants delivered at Kurashiki Central Hospital Perinatal Center during April 1979 to March 1983. The very premature singleton infants without congenital anomaly were studied in the present work, including 45 live-birth infants born at 24 to 32 weeks of gestation and weighing 590 to 2,000g at birth. The mortality rate for male infants was higher than that for female infants, but this difference was not statistically significant. The mortality rate for infants born at 28 to 32 weeks of gestation was 2.9%, and that for infants weighing 1,000g or more at birth, respectively. The cause of all these neonatal death was massive aspiration syndrome with intracranial hemorrhage, and severe neonatal asphyxia. The mortality rate for infants born at 24 to 32 weeks of gestation was 60%, and that of infants weighing 999g or less, 60%, respectively. The cause of all these neonatal deaths was respiratory distress syndrome with intracranial hemorrhage. Clinically, it was suggested that cesarean section after onset of labor, PROM, and Betamethasone prior to delivery increased the survival rate of these infants statistically significantly. The most important neonatal complication in the prognosis of very premature infants was intracranial hemorrhage. The most correlated perinatal factors of neonatal intracranial hemorrhage were one min. Apgar score and fetal lung maturation.     

Impact of infants born at the threshold of viability on the neonatal mortality rate in Colorado.

OBJECTIVE: To determine the contribution of infants born at the threshold of viability (< 750 gm) on neonatal mortality in Colorado. STUDY DESIGN: For the period of January 1991 to December 1996, all Colorado live births who expired were evaluated for gestational age, birth weight, gender, hospital level of care, age at time of death, delivery room resuscitation, mechanical ventilation, medical and surgical complications, and serious malformations. RESULTS: Although infants weighing < 750 gm represent only 0.31% of all live births, they account for 46.3% of deaths. While those infants weighing < 500 gm and with a gestation of < 24 weeks almost always died (94.7%), the majority born in the 500- to 745-gm category (55.8%) survived. The vast majority (88.5%) of deaths occurred on the first day of life. A total of 38.4% of births in which the infant weighed < 750 gm occurred outside bona fide regional perinatal centers. CONCLUSION: Future attempts to reduce the Colorado neonatal mortality rate would best focus on the 500- to 750-gm weight group through the re-regionalization of high-risk perinatal care.     

Time of birth and the risk of neonatal death

OBJECTIVE: To assess whether mortality is increased in the United States in infants born at night, we compared case-mix adjusted neonatal mortality for low- and high-risk infants born during the daytime (7 am to 6 pm), early night (7 pm to 12 am), and late night (1 am to 6 am). METHODS: California linked birth-death certificate data on 3,363,157 infants, weighing more than 500 g and born without lethal congenital anomalies in 1992-1999, were analyzed. Logistic regression, adjusting for birth weight, gender, prenatal care initiation, maternal hypertension, eclampsia, diabetes, and placental abruption/previa, was used to estimate the relationship between neonatal mortality and time of birth. RESULTS: The overall neonatal mortality was 2.08 deaths per 1,000 live births. Neonatal mortality was 1.88 for daytime births, increasing to 2.37 for early night and 2.31 for late night births. After adjusting for case mix, early night births had a 12% increase and late night births a 16% increase in the odds of neonatal death, an excess that accounts for 9.6% of all neonatal deaths. Mortality was increased for night births that were less than 1,500 g or more than 1,500 g, singletons or multiples, and those delivered vaginally or by cesarean. The increased risk was identified in hospitals that provide intermediate, community, and regional neonatal intensive care, but not in hospitals that provide primary care. CONCLUSION: Identifying the causal factors and reducing the increased burden of mortality for infants born at night should be a major priority for perinatal medicine.     

Improved survival and neurodevelopmental outcome for infants less than 801 grams birthweight

We reviewed the perinatal management and subsequent outcome of infants 401 to 800 gm birthweight delivered in 1983 to 1985 compared with those born in 1980 to 1982. Intrapartum fetal heart rate monitoring, cesarean section delivery, attempted delivery room resuscitation, and 5-minute Apgar scores greater than 5 were more frequent in 1983 to 1985. Significantly greater neonatal survival was evident for infants 500 to 700 gm birthweight (31%) and 24 to 27 weeks' gestation (45%) in 1983 to 1985, p less than 0.005. Infant birthweight, gestational age, gender, and 5-minute Apgar score, in addition to intrapartum tocolysis use, were predictors of higher survival by stepwise discriminant analysis. At a mean follow-up of 27 months, 13% (6 of 46) born in 1983 to 1985 had major disability compared with 67% (6 of 9) of infants born in 1980 to 1982. There has been a significant increase in survival and improvement in neurodevelopmental follow-up status for infants less than 801 gm birthweight. These improved outcome data should be considered by caregivers providing perinatal management and counseling parents regarding extremely low birthweight infants.     

The effect of cesarean delivery on birth outcome in very low birth weight infants. National Institute of Child Health and Human Development Neonatal Research Network

To determine whether cesarean delivery is associated with a better outcome than vaginal delivery for infants weighing less than 1500 g (very low birth weight), we examined neonatal mortality and the incidence of intraventricular hemorrhage (IVH) in 1765 very low birth weight inborn infants admitted to seven neonatal intensive care centers. The cesarean rate was 32.5% for infants weighing 501-750 g and 52.4% for infants weighing 751-1000 g. The neonatal death rate was 53.1% for infants weighing 501-750 g delivered by cesarean, compared with 64.3% for vaginally born infants (P = .046). However, for infants weighing 1001-1250 g, the neonatal death rate for infants delivered by cesarean was 14.4%, compared with 7.8% for infants born vaginally (P = .02). The incidence of IVH was significantly lower in infants born by cesarean than in those born vaginally only in the 1251-1500-g birth weight interval (11.8 versus 18.9%; P = .03). Compared with women delivering vaginally, those delivered by cesarean were more likely to attain a higher mean gestation, to have preeclampsia, and to have a breech presentation, and less likely to be in labor. After adjusting by logistic regression for gestational age, preeclampsia, breech presentation, presence or absence of labor, and for center effects, the odds ratio for neonatal death was 1.00 (95% confidence interval 0.71-1.41); for IVH, the odds ratio was 0.85 (95% confidence interval 0.61-1.19). These data suggest that after accounting for certain maternal and fetal factors, cesarean delivery is not associated with a lower risk of either mortality or IVH.     

Neonatal mortality in normal birth weight babies: does the level of hospital care make a difference?

Although neonatal intensive care for low birth weight infants has been extensively studied, few researchers have looked at the impact of the level of care at the delivery hospital for infants weighing greater than 2500 gm. Using linked birth-death records from Georgia for 1979 to 1982, we examined the effect that the level of care available at the hospital of delivery had on neonatal mortality in infants weighing 2500 gm and above. We used a risk scoring system designed for use with vital records to determine prepartum risk and the presence or absence of a complication of labor as indicated on the birth certificate to determine intrapartum risk. We found that women with a high prepartum risk score had increased neonatal mortality at level 1 hospitals. Women who developed a complication of labor, regardless of their prepartum risk status, had the highest neonatal mortality rates when they delivered at level 1 hospitals. We suggest prenatal risk assessment for all women and referral of high risk women to level 2 or 3 hospitals for delivery even at term.     

The cost of care of the less-than-1000-gram infant

One of the most difficult ethical issues in neonatal intensive care concerns the treatment of extremely low birth weight infants (ELBW). Because of their extreme prematurity, aggressive medical intervention is needed to sustain life. Advances in perinatal medicine have made it possible for these extremely immature infants to survive. More importantly, although the mortality and long-term morbidity are high, particularly for infants less than 700 gm, many of the survivors are expected to become productive members of society and produce measurable economic benefit. The limits set for aggressive management of the VLBW infant have gradually been lowered in virtue of the successful survival at each birth weight. It appears that, with each reduction in the birth weight at which maximal efforts should be used, enough babies have survived to encourage us to continue. As we drive to bring the limit of viability to lower gestations and lower birth weights, we are finding some biologic limitations to extrauterine survival that present technology and knowledge cannot overcome. Unquestionably, there is a need for more comprehensive statistics to allow us to define the lower limit of survival. Because of the poor survival rate among infants weighing less than 700 gm, and because of the high cost of their care and statistically poor quality of life among many of the surviving infants, it has been suggested that perhaps a less aggressive approach should be adopted for those extremely immature infants. However, some recent data indicate that aggressive treatment is effective in saving lives, even at the lower spectrum of birth weight, and many of the survivors are normal or have mild handicaps. The importance of economic considerations to solve the ethical dilemma posed by the intensive care of ELBW infants is being questioned. Concerns that reflect moral absolutes cannot be adequately answered in terms of mere dollars and cents. Although the cost of neonatal intensive care is high on a per diem or per case basis, it appears to be reasonable in relation to the health benefits it provides. For infants in the weight class less than 750 gm, probably none would have survived in the absence of neonatal intensive care. We believe that a policy of benign neglect for the ELBW infant is not justified in the present era of perinatal medicine. Given these considerations, we think that aggressive treatment is reasonable, at least initially at birth.(ABSTRACT TRUNCATED AT 400 WORDS)     

Survival and ventilatory course of a regional cohort of very low birthweight (501-1500 gm) infants

To minimize the selection bias inherent in reporting results gathered only in neonatal intensive care units, this study presents survival and respiratory course data on all 299 infants of birthweight 501 to 1500 gm liveborn to residents of the North Central Illinois Perinatal Region in 1985-1986. The survival rate was 86.8% (171 of 197) for infants between 1001 and 1500 gm, but only 35.3% (36 of 102) for infants weighing less than 1001 gm. In all, 207 infants (69.2%) survived. One hundred eighty-six infants (62.2%) required mechanical ventilation, and 122 (65.6%) ventilated infants survived. Seventy-five (40.3%) ventilated infants developed lung rupture and 54 (29%) developed chronic lung disease (CLD), as manifest by a supplemental oxygen requirement at 28 days of age. Lung rupture significantly predicted death in the first 7 days, the development of CLD, and fatal CLD. These data portray an accurate picture of the survival and ventilatory course of this group of babies because every member of the entire regional cohort is included.     

Outcome of neonates with birth weights of less than 801 grams

The follow-up results of intensive care for 68 infants with birth weights less than 801 g treated at Stanford University Hospital were reviewed. The overall survival rate for these infants was 35%, but was 50% for those infants who had been successfully resuscitated in the delivery room and were admitted to the Intensive Care Nursery. Infants under 601 g in weight or less than 25 weeks gestation were more likely to die in the delivery room, but survival among those admitted to the Intensive Care Nursery did not depend on birth weight or gestational age. One-minute and 5-minute Apgar scores less than 5 and interstitial emphysema were associated with increased risk of neonatal death. Only two of 22 survivors (9%) were severely handicapped and another eight (36%) had remediable disabilities at 2 years of age. No infant developed hydrocephalus and only one infant had spasticity. We suggest that the low incidence of major handicaps among survivors encourages the vigorous resuscitation of infants weighing less than 801 g at birth, yet strategies must be developed that will minimize both prolonged dying and the cost of intensive care for nonviable infants.     

Placenta previa: aggressive expectant management

We report the outcomes of 95 expectantly managed cases of placenta previa; all were diagnosed after 21 weeks' gestation. Patients at risk for preterm delivery because of hemorrhage or preterm labor received aggressive care, including multiple transfusions, volume expansion and tocolytic therapy, and amniotic fluid surfactant determinations, to achieve the goal of delivery at 37 weeks' gestation with mature fetal lung function. We present guidelines for outpatient management and double setup examination prior to delivery. The role of ultrasound in diagnosis (three asymptomatic cases; 13 cases with preterm labor) and serial placental localization to determine the timing, route, and place of delivery is presented. Eighty-six percent of 19 infants born weighing less than 2500 gm were managed expectantly. Hemorrhage was the determinant in delivery timing in 50 cases. All four deaths were neonatal with birth weights less than 2200 gm. This is the lowest perinatal mortality rate (4.2%) published to date. Use of this aggressive approach is particularly suitable for patients cared for in a teritary center.     

The NICHD neonatal research network: changes in practice and outcomes during the first 15 years

The National Institute of Child Health and Human Development (NICHD) Neonatal Research Network was founded in 1986 to perform trials that, because of their size and complexity, were beyond the scope of a single center and required the expertise and resources of many collaborating centers. This report briefly documents changes in mortality, selected morbidities, and therapies amongst Network centers. The Network registry incorporating perinatal and neonatal data on all infants with a birth weight 501-1500 g cared for at participating centers served as the database. Mortality and selected morbidities were compared for 3 time periods, 1987/1988, (7 centers 1,765 infants, presurfactant); 1993/1994 (12 centers, 4,593 infants, postsurfactant and moderate antenatal corticosteroid utilization); and 1999/2000 (15 centers, 5,848 infants, postsurfactant and widespread corticosteroid use). Detailed outcomes for infants with birth weights between 501 and 800 g, and gestational ages of 23 to 25 weeks are also presented because they dramatically document the changes over time. Mortality for the entire cohort decreased from 23% in 1987/1988 to 17% in 1993/1994 and 14% in 1999/2000. Between 1987/1988 and 1999/2000 mortality prior to discharge, decreased from 66% to 45% for infants weighing 501-750 g; from 34% to 12% for birth weight between 751 to 1000 g, and from 13% to 7% for infants between 1001 and 1500 g. Mortality was higher in boys. Survival free of major morbidity (chronic lung disease/bronchopulmonary dysplasia, necrotizing enterocolitis or grade III/IV intraventricular hemorrhage) did not change significantly over time. Since the inception of the Network, multiple births have increased from 18% to 26%; deliveries by Cesarean section from 47% to 57%, and antenatal corticosteroid use increased from 16% to 79%. Surfactant, which was not used prior to 1990, is now given to 57% of the infants, including 87% with birth weights between 501 and 750 g. There have been significant decreases in the incidence of grade III-IV intraventricular hemorrhage from 18% in 1987/1988 to about 11% since 1993/1994, and periventricular leukomalacia from 8% to 3%. However, other morbidities, including necrotizing enterocolitis, patent ductus arteriosus, and late onset sepsis, have not changed substantially. Advances in perinatal care within NICHD Network centers have resulted in marked improvements in survival. Further advances are required to increase survival free of neonatal morbidity or neurodevelopmental impairment.     

Factors affecting the sex differential in neonatal mortality: the role of respiratory distress syndrome

We investigated factors affecting the sex differential in neonatal mortality rate using linked birth and death certificates of more than 300,000 infants born in Georgia between 1974 and 1977. The neonatal mortality rate was higher in male infants than in female infants (relative risk = 1.23, p less than 10(-8)) and was most pronounced for infants weighing between 1501 and 2500 gm (relative risk = 1.78, p less than 10(-8)). This differential persisted after adjustment was made for effects of several prenatal and labor-related factors. The male excess in neonatal mortality rate was most prominent during the first week of life and was found for several perinatal disorders. Respiratory distress syndrome-related mortality showed the largest male excess (relative risk = 1.57, p less than 10(-8)) and was most pronounced in infants weighing between 1501 and 2500 gm (relative risk = 2.78, p less than 10(-8)), in whom it accounted for roughly 60% of the excess. Since previous studies have shown that male infants have a higher incidence of respiratory distress syndrome but not a higher case-fatality rate, we suggest that slower lung maturation among male fetuses is a major contributing factor to the sex differential in neonatal mortality.     

Effectiveness of neonatal transport systems

In order to assess the effectiveness of neonatal transport systems, morbidity on admission and early neonatal mortality of low birth weight infants below 2000 gm were studied. All infants referred to a neonatal department in Munich or Southern Bavaria from 1979 to 1981 were included. The data of infants born in Munich perinatal centers were compared to those of infants delivered in hospitals in the Munich area (radius 30 km) and in other hospitals in Southern Bavaria. Ninety-four percent of 248 LBW neonates born in the Munich perinatal centers, 87.5% of 736 infants and 84.4% of 681 LBW infants from the Munich area and Southern Bavaria respectively survived the first week of life although the morbidity risks of inborn infants were higher than those of the outborn. The presence of a pediatrician at birth and during neonatal transport to an NICU did not improve survival rates of infants delivered outside the perinatal centers. The effectiveness of neonatal transport systems is limited. They should be complemented by a maternal transport system, i.e., an infant transport in utero for cases in which the necessity for intensive neonatal care is expected.     

Obstetric factors influencing outcome in infants weighing from 1,001 to 1,500 grams.

The neonatal mortality rate has dramatically improved in recent years. Occurrence of these losses is concentrated in low-birth-weight infants. At Los Angeles County-University of Southern California Medical Center, the infants weighing less than 1,500 grams contribute two thirds of neonatal deaths, although they may represent only 1.5 per cent of total births. Such observations have led to the evaluation of obstetric factors as they relate to the outcome in the low-birth-weight infants weighing from 1,001 to 1,500 grams. Retrospective evaluation of 201 low-birth-weight-infants' charts demonstrated a tendency by the obstetrician to clinically underestimate fetal weight. In cases where fetal estimated weight and measured birth weight correlated, the mortality rate was 20 per cent; in cases of underestimation, the mortality rate rose to 50 per cent. Other obstetric factors evaluated were the use of FHR monitoring, the method of delivery, and the significance of the Apgar score.     

A clinical study on the prognosis of infants born by breech delivery

The influence of breech and vertex delivery on intrapartum fetal and neonatal mortality was studied in 8,863 infants delivered at Kurashiki Central Hospital Perinatal Center. The rate of mortality was studied in cases without fatal congenital anomalies. The frequency of congenital anomaly was also studied in 8,863 infants delivered by breech and vertex presentation. Infants were divided into five groups according to their birth weight: 99g or less, 1,000-1,499g, 1,500-1,999g, 2,000-2,499g and 2,500g or more. Infants were also grouped into four by gestational age: 24-27 weeks, 28-31 weeks, 32-36 weeks and 37 weeks or more. The total infant mortality rate was 4.9% in breech delivery, and 0.5% in vertex delivery, respectively. This difference was statistically significant. The rate of major congenital anomaly in breech delivery was significantly higher than in vertex delivery. The rate of premature deliveries in breech presentation was also significantly higher than in vertex delivery. The rate of mortality in the group weighing 1,000-1,499g was 50.0% in breech delivery, and 17.6% in vertex delivery, respectively. This difference was statistically significant. The rate of mortality in the group delivered at 28-31 weeks gestational age was 62.5% in breech delivery, and 15.4% in vertex delivery, respectively (statistically significant). The rate of severe neonatal asphyxia in infants delivered at 28-31 weeks of gestational age was significantly higher in breech delivery than in vertex delivery.