Birth Weight-specific Mortality Research Articles

Birthweight Specific Perinatal Mortality in Greece

Data from the Greek Perinatal Study in April 1983 revealed an excessively high perinatal mortality rate of 21.6 per 1,000 total births among singletons despite a low birthweight rate of only 4.5%. Comparison of perinatal mortality rates with Danish mortality rates in 1983, revealed the Greek rates to be three times higher than those in Denmark. When divided by time of death, the Greek stillbirth rates were two times higher and the early neonatal mortality rates were four times higher than the corresponding Danish rates. Subdivision of the Greek perinatal deaths using the Wigglesworth classification showed that the biggest group (40%) consisted of deaths associated with intrapartum asphyxia. The incidence of such deaths was 10 times higher than that found in Denmark. We conclude that in reducing the excessively high perinatal mortality rate in Greece special attention should be made to improve intrapartum and resuscitation techniques.

Socioeconomic Differentials and Neonatal Mortality: Racial Comparison of California Singletons

The median family income of the zip code of maternal residence was used to estimate the presence and determine the extent of socioeconomic differentials in the neonatal mortality rates of a cohort of 401,399 white and of 66,577 black Californian singletons born from 1982 to 1983. The neonatal mortality rate in the white infants increased from 3.99 in mothers residing in zip codes with a median family income greater than $25,000 to 12.1 for mothers residing in zip codes with a median family income less than $11,000. With decreasing socioeconomic status there was also a significant increase in the percentage of white infants weighing less than 2,500 g (percentage of low birth weight increased from 3.75 to 8.33) and weighing less than 1,500 g (percentage of very low birth weight increased from 0.56 to 1.46). When the source of the socioeconomic difference in white neonatal mortality was partitioned, 77.4% was due to deterioration in the birth weight distribution and 22.6% to deterioration in the birth weight-specific mortality rates. For the black cohort, the neonatal mortality rate increased from 5.9 in the most, to 9.0 in the least affluent strata. Although decreasing residential median family income was associated with an increase in the percent low birth weight (8.19 v 12.86), the percentage of very low birth weight was not significantly different (1.59 v 2.10). When the source of the differential in black neonatal mortality was partitioned, only 29% was due to deterioration of the birth weight distribution, whereas 71% was secondary to less favorable birth weight-specific mortality rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Perinatal mortality in twin pregnancy: an analysis of birth weight-specific mortality rates and adjusted mortality rates for birth weight distributions.

The objective of this study is to compare the fetal mortality rate (FMR), early neonatal mortality rate (ENMR) and perinatal mortality rate (PMR) of twin and single births. It is based on a survey which was carried out in 22 Hospital Centers in Spain in 1980, and covered 1,956 twins born and 110,734 singletons born. The FMR in twins was 36.3/1000 and 8.8/1000 for singletons. The ENMR in twins was 36.1/1000 and 5.7/1000 for singletons. The PMR in twins was 71.1/1000 and 14.4/1000 for singletons. When birthweight-specific PMR in twin and singletons births are compared, there were no differences between the rates for groups 500-999 g and 1000-1499 g. For birthweight groups of 1500-1999 g (124.4 vs 283.8/1000) and 2000-2999 g (29.6 vs 73.2/1000) the rates for twins were about twice lower than those for single births. The PMR for 2500 g and over birthweight was about twice higher in twins than in singletons (12.5 vs 5.5/1000). After we adjusted for birthweight there was a difference in the FMR (12.6 vs 9.8/1000) and the PMR (19.1 vs 16.0/1000, and no difference in the ENMR between twins and singletons (5.9 vs 6.4/1000), indicating that most of the differences among crude rates are due to differences in distribution of birthweight.

Perinatal Statistics

To the Editor.— Evaluation of the effect of good medical care of pregnant women and newborn infants and/or the impact of birth weight distribution on crude perinatal mortality rates is based upon the use of birth weight-specific mortality rates and standardized perinatal mortality rates.1-4 We agree with the suggestion made by Hermansen and Hasan5 that all future reports on perinatal statistics should comply with the recommendations made by WHO. Moreover, meaningful comparisons of standardized perinatal mortality rates over time and place require the use of a standard birth weight distribution.

602 THE EFFECT OF PRENATAL CARE UPON BIRTH WEIGHT SPECIFIC OUTCOME

It is generally accepted that variations in birth weight-specific mortality rates (BWSMR) are closely related to the nature and quality of medical care provided the neonate once born. However, the effect of prenatal care on BWSMR has not been well explored. We studied linked birth/neonatal death vital statistics files for the City of Boston for the years 1975–79. Logistic models were used to assess the influence of prenatal care adjusting for race, gestational age, maternal age, education, and family income. For the 329 deaths and 68,842 births analyzed, prenatal care was significantly related to overall neonatal survival (p < .001). However, its effect upon BWSMR was not uniformly significant: The data suggest that prenatal care does not greatly influence BWSMR at low birth weights. However, the adequacy of prenatal care services appears to strongly affect survival at birth weights above 2500g. Alterations in access to prenatal care could therefore influence both the distribution of low birth weight (LBW) births and the BWSMR of non-LBW neonates.

Fetal growth and perinatal mortality in twin pregnancy - effect of sick leave and hospitalization

Fetal growth, birth weight specific mortality rates and effect of sick leave or hospitalization on the fetal growth were investigated in a material of 476 twin pregnancies managed at University Central Hospital of Turku in year 1970–1981. Birth weights of twin babies at any gestational age were slightly but not significantly higher than in earlier materials. When compared to growth curve of singleton fetuses, the growth rate of both twins is equal to singletons up to 30th week of pregnancy, being thereafter slower than in singleton pregnancies. Although duration of sick leave and hospitalization increased considerably during the study period, no change in the duration of pregnancy nor in the weight of twin babies occurred. Instead perinatal mortality decreased from 101/per thousand to 36.2/ per thousand. Birth weight specific mortality rates did not differ from those in singleton fetuses.

551 SUDDEN INFANT DEATH IN INTENSIVE CARE UNIT GRADUATES

The graduates of neonatal intensive care units (NICU) are a group of high risk infants. Few studies have documented the risk of sudden infant death syndrome (SIDS) in this special group of infants. We decided to document the incidence of SIDS and some risk factors associated with it as part of our High Risk Infant Follow-up Program, since January 1980 to September 1984, 917 infants have been discharged from our NICU. Eight infants died of SIDS during this period with an incidence of 0.87% among total NICU graduates. Further division into birth weight specific SIDS mortality rate revealed 3.8% (2/53) for BW between 500-1000 gm, 2.5% (3/120) for BW between 1001 to 1500 gm, 2.9% (5/173) for BW between 500 to 1500 gm 0.3% (1/348) for BW between 1500 to 2500 gm and 0.5% (2/396) for BW of >2500 gm. Mean age at death was 4 months, ranging from 1 to 6 months of age. Fifty percent of the deaths occurred in the winter season. Significant associated risk factors included low socioeconomic status (75% of SID infants), single mothers (62.5%), and race (50% black, 25% Hispanic, and 25% white). There was an equal distribution of sexes. This study reveals a 4 fold increase in the risk of SIDS in NICU graduates and 15 times increased risk in the VLBW infants of NICU graduates compared to that of general infant population.

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.

A controlled evaluation of rural regional perinatal care: impact on mortality and morbidity.

The impact of a rural regional perinatal care (RPC) program was assessed by a quasi-experimental, controlled, population-based design. Outcome measures included changes in five-year average fetal and neonatal mortality rates as well as short-term obstetric and newborn morbidity. Declines in fetal and neonatal as well as birthweight specific mortality rates were observed for both pilot and control regions, for both races, and especially for 1501-2500 g infants. However, comparisons of preprogram (1966-74) and postprogram (1975-80) average yearly changes showed no statistically significant differences between regions. While the incidence of prenatal morbidity was the same for both regions, intrapartum and newborn morbidity significantly favored the pilot region. These results were difficult to interpret. Program relevant implications of the findings in relation to rural RPC in North Carolina are discussed. Specific benefits appeared to be associated with the development of two high-risk maternity clinics and a Level II center capability in the pilot region. The importance of community support and public/private sector cooperation in relation to RPC is noted.

Neonatal mortality in infants born weighing 501 to 1000 grams

Abstract 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.

Mortality in the first week of life and mode of delivery.

11 923 singletons with birthweight greater than 775 g born consecutively at the 2nd School of Medicine of Naples during a four-year period (November 1975 to October 1979) were the subjects of the study. Mortality in the first week of life was 10.9, 9.7, 6.7 and 10.7 per 1 000 respectively in the four years. The total variability of the crude death rates was reduced by 21.4% after standardization for birthweight distribution alone and by 28.6% when both birthweight and mode of delivery were taken into account. Therefore only a small fraction of the variations in mortality can be ascribed to changes in the distribution of modes of delivery during the study period. Most of these variations are probably related to the quality of perinatal care, which seems to have improved only for babies under 1 526 g. Birthweight specific mortality in relation to mode of delivery is further discussed.

The use of standardized neonatal mortality ratios to assess the quality of perinatal care in Colorado

Neonatal mortality in Colorado in the 3-year period 1977-1979 has been analyzed by means of standardized neonatal mortality ratios derived from birth weight-specific mortality for every obstetric facility. The standardized neonatal mortality ratios adjusted for the percentage of neonatal deaths due to untreatable disorders are presented as one possible method for comparing the neonatal outcome in obstetric populations of dissimilar risk. We have suggested that facilities with adjusted standardized neonatal mortality ratios significantly above 1 are those that might benefit from an in-depth review of perinatal services.

Perinatal mortality in a large perinatal center: Five-Year review of 31,000 births

The perinatal mortality rate for 30,928 babies born at Medical Center Hospital, San Antonio, Texas, between 1978 and 1982, was 20.3/1,000 births. Neonatal and fetal mortality rates were, respectively, 10.1/1,000 live births and 10.4/1,000 births. Exclusion of babies who weighed less than 500 gm yielded adjusted fetal, neonatal, and perinatal mortality rates of, respectively, 9.2, 9.8, and 17.9. Birth weight-specific mortality rates were calculated by groups of 250 gm birth weight for all neonates and by increments of 100 gm for babies who weighed 500 to 1,499 gm. Male infants, intrauterine growth-retarded babies, and babies whose mothers were less than 15 years old contributed more deaths than would be expected from the characteristics of the obstetric population. Presumptive cause of fetal death was unknown in 32%, fetal anoxia in 21%, maternal pathologic conditions in 20%, inappropriate fetal growth in 13%, congenital malformations in 8%, and systemic fetal infections in 6%. Leading presumptive causes of neonatal death were immaturity (29%), congenital malformations (18%), hemorrhages (16%), and systemic infections (10%). Hyaline membrane disease and necrotizing enterocolitis contributed, respectively, 7% and 6% of deaths. Past and future trends of perinatal mortality are discussed.

Decline in Neonatal Mortality, 1968 to 1977: Better Babies or Better Care?

A state's declining neonatal mortality rate was studied over the decade 1968 to 1977 to determine how much of the decrease resulted from improved risk characteristics in the newborn population. A shift was found over time, mostly among white births, toward higher birth weights and longer gestations. Overall, there was a 19% reduction in the low-birth-weight rate. Considerable improvement in birth weight-specific mortality was also found, especially in babies weighing 1,000 to 2,500 g during the last 5 years of the study. A neonatal risk matrix model was applied to the changes over time to separate the improvement due to shifts in population risk characteristics from that due to better care of the newborn. Thirty-four percent of the decade's decrease in NMR was attributable to changes in the birth weight and gestational age makeup of the newborn population. This "better babies" component was more prominent early in the decade and among the white population.

Completeness of infant death registration for very low birthweight infants: Washington State 1978-79.

Washington State hospitals were queried about the fate of 507 infants born in 1978-79 for whom no linked death certificate existed. Only ten previously unregistered deaths were discovered, raising mortality for this group by 2.5 per cent. In addition, 13 previously unmatched death records were linked to birth records, providing more accurate calculation of birthweight-specific mortality rates. Washington State infant death registration is more complete that that found in either Georgia or North Carolina.

Monitoring perinatal mortality by birth weight specific mortality rates

The perinatal mortality at University Central Hospital of Turku, Finland decreased significantly from 15.7/1000 in years 1970–1975 to 8.9/1000 in years 1976–1978. The main decrease has occurred in weight groups of 1000 g and more. In years 1976–1978 the perinatal mortality of non-malformed babies in the weight group 1500–1999 g was 93 1000 , in the group 2000–2499 g 21 1000 and in the group of 2500 g and over 1.7/1000. The early neonatal mortality of non-malformed infants has decreased significantly only in the weight group of 1500–1999 g. The 1-week survival rate has been 48% in the weight group 500–999 g, but 77% in the weight group 1000–1499 g. The birth weight specific mortality rates are greatly required when the quality of obstetrical care is assessed. Birth weight specific neonatal mortality rates are essential when guidelines for elective termination of third trimester pregnancy are designed.

Indirect standardization of neonatal mortality for birth weight.

Recent advances in perinatal medicine, together with the proliferation of regionalized perinatal networks, have increased the need for monitoring of trends and variations in birth weight-specific perinatal mortality rates. Since the United states has no national system of linked birth and death records, the only available method for comparing weight-specific mortality among geographic areas or medical care facilities in through indirect standardization of mortality for birth weight. This paper investigates the characteristics of the Standardized Mortality Ratio (SMR) obtained by indirect standardization using 1974-77 neonatal mortality and birth weight data for 202 geographic areas across the United States. The results show that the SMR is not sensitive to the choice of standard rates even when the area's birth weight-specific mortality rates are not a constant multiple of standard rates. A method for estimating the standard error of the SMR without knowledge of the weight-specific rates is presented and shown to be nearly unbiased. There is also a substantial amount of variation among geographic areas in both neonatal mortality rates, SMRs, and birth weight distributions. Thus, despite certain limitations, the SMR provides a useful summary measure for monitoring trends and variations among geographic areas or medical care facilities in birth outcome.

Regional variations in perineonatal mortality

Regional variations in fetal outcome have been assessed by means of birthweight specific mortality rates calculated from routinely collected data. Implications for medical audit are outlined.

Neonatal mortality: an analysis of the recent improvement in the United States.

To test the hypothesis that the recent substantial decline in the United States neonatal mortality rate (20.0/1000 in 1950 to 11.6/1000 in 1975) is associated with improvements in perinatal medical care, we examined this change in relation to the two primary components which determine neonatal mortality: birthweight distribution and birthweight-specific mortality. No improvement in the weight distribution of U.S. live births has occurred during this 25-year period, indicating that the change in neonatal mortality is attributable to improved survival for one or more birthweight groups. Decline in the mortality rate in the first 15 years was slow; three-fourths of the decline in the entire 25-year period occurred since 1965. With the exception of perinatal medical care, factors known to affect survival at a given birthweight have not changed in prevalence in the 25-year period. It is a plausible hypothesis that improved perinatal medical care is a major factor in declining neonatal mortality in the U.S.

PERINATAL MORTALITY IN SWEDEN: Analyses with International Aspects

The perinatal mortality in Sweden has been decreasing during the last four decades. From available vital statistics in 1976 Sweden's figures are the lowest internationally. The decline continues and in 1978 the figure was as low as 10.0 per thousand. The five-year period 1973--1977 has been specially analysed using medical birth records from all births. Data from an international perinatal study in 1973 coordinated by WHO have been treated in the same way. With birth weight (BW) specific mortality rates in groups of 250 g it is shown that late fetal deaths (LFD) are related to BW only for high BW and that early neonatal deaths (END) are inversly related to BW. There is no sex difference in LFD but a marked male dominance in END, with one third higher rate for the boys. BW specific mortality rates in BW groups of 250 g, separated in LFD and END can be used as a tool for evaluating the quality of perinatal care. The influence oof factors related to patterns and standards of living is emphasized. It is suggested that perinatal mortality should be given in its two components separately late fetal death rates (LFD) and early neonatal death rates (END).