THE JOURNAL OF
PEDIATRICS AUGUST
1967
V o l u m e 71
Number 2
A practical classification of newborn infants by weight and gestational age A classification of newborn infants based upon gestational age and birth weight is proposed,. The advantages o[ establishing such a routine on a nursery service, and the possibility o[ superimposing neonatal mortality rates upon gestational-age and birth-weight data are presented.
Frederick C. Battaglia, M.D., and Lula O. Lubchenco, M.D. DENVER,
COLO.
T I ~ E u s e o F some system on a nursery service which facilitates the recognition of infants born with birth weights disproportionate for their gestational age, either too large or too small, is becoming increasingly important in pediatrics. Different clinical problems develop in infants of the same birth weight, but different gestational ages. Furthermore, the identification of a high-risk newborn group is facilitated by the use of gestational age information, as well as birth weight information. While gestational age information is helpful in the identification of newborn infants at high risk, its widespread use will depend in From the Departments of Pediatrics and Obstetrics and Gynecology, University of Colorado Medical Center. Supported by Public Health Service Grants HD00781-03 and HD00373 and the Children's Bureau in cooperation with the Colorado State Department of Public Health and the University of Colorado Medical Center. Present Address, University o[ Colorado Medical Center, 4200 East 9th Ave. Denver, Colo., 80220.
great part upon establishing some convenient method of coding and classifying them by birth weight and gestational age shortly upon admission to the nursery service (Table I, See Editor's Column, p. 309 Fig. 2). In essence, this classification divides newborn infants into 9 groups, 3 by gestational age, and within each of these groups, 3 subgroups by birth weight. S U B D I V I S I O N S BY G E S T A T I O N A L AGE In accordance with recent recommendations of the Committee on the Fetus and Newborn of the American Academy of Pediatrics, the 3 basic divisions by gestational age have been referred to as Pre-Term, Term, and Post-Term. Assuming two weeks as a reasonable error of the estimated gestational age based upon the first day of the last menstrual period, Term has been referred to as Vol. 7I, No. 2, pp. 159-163
160
Battaglia and Lubchenco
The Journal o[ Pediatrics August 1967
T a b l e I, I n s t r u c t i o n s for use of classification study
Part I: Description o[ chart 1. Neonatal mortality risk (NMR): There are 4 colored zones shown: White Yellow Blue Red
mE infants infants z infants infants
with with with with
< 4% 4%-25% 25%-50% > 50%
2. GA-BW distribution: GA to be estimated from 1st day of LMP and classified by completed weeks: 37 weeks + 0 days = 37 weeks + 6 days = GA: Subdivided along abscissa into 3 categories:
NMR NMR NMR NMR
37 weeks 37 weeks
a. Pre-Term (Pr) ~ All infants less than 38 weeks GA, i.e., 37 weeks + 6 days or less. b. Term (T) ~ All infants between 38th and 42nd weeks GA. c. Post-Term (Po) ~- All infants of 42 or more weeks GA. BW: Within each GA group, there are defined 3 subgroups of infants by BW: a. LGA ~ Infants above 90th percentile. b. AGA ~--- Infants between 90th and 10th percentile. c. SGA ~ Infants below 10th percentile. Thus, 9 groups of newborn infants are defined and coded as follows: Pr-LGA Pr-AGA Pr-SGA T-LGA T-AGA T-SGA Po-LGA Po-AGA Po-SGA
Born Born Born Born Born Born Born Born Born
before 38th week, BW above 90th percentile. before 38th week, BW between 10th and 90th percentile. before 38th week, BW below 10th percentile. between 38th and 42nd weeks, BW above 90th percentile. between 38th and 42nd weeks, BW between 10th and 90tb percentile between 38th and 42nd weeks, BW below 10th percentile. at or after 42nd week, BW above 90th percentile. at or after 42nd week, BW between 10th and 90th percentiles. at or after 42nd week, BW below 10th percentile.
Part H: Instructions I. Shortly after delivery, newborn is to be plotted by GA and BW on above chart; check GA estimate from 1st day of LMP. 2. Colored tape signifying mortality range (white, yellow, blue, or red) of this infant placed on isolette or bassinet and on chart. 3. Write on colored tape, 1 set of initials applicable to that infant signifying which one of 9 possible categories he fails into, e.g., T-AGA. 4. Thus: color of tape ~ mortality subgroup initials on tape ~ GA and BW subgroup. 5. All infants falling on line dividing 2 zones should be coded as in zone with the highest risk, e.g., infant of 32 completed weeks GA falling on 10th percentile line should be coded as Pr-SGA.
encompassing
all infants
born
with
gesta-
t i o n a l ages f r o m t h e t h i r t y - e i g h t h c o m p l e t e d w e e k u p to b u t n o t i n c l u d i n g t h e f o r t y - s e c o n d c o m p l e t e d week. T h u s , all infants b o r n before 38 c o m p l e t e d weeks are r e f e r r e d to as P r e - T e r m , a n d all b o r n a f t e r the forty-first c o m p l e t e d w e e k as P o s t - T e r m . SUBDIVISIONS BY BIRTH WEIGHT S e v e r a l reports h a v e b e e n p u b l i s h e d recently establishing a f r e q u e n c y distribution of i n f a n t b i r t h weights at v a r i o u s gestational
ages. 1-6 T h e s e studies h a v e b e e n c a r r i e d o u t on w i d e l y d i f f e r e n t p o p u l a t i o n groups. I t is not surprising, therefore, t h a t s o m e striking differences in t h e f r e q u e n c y distribution of i n f a n t b i r t h w e i g h t ' s at various gestational ages h a v e b e e n f o u n d . H o w e v e r , this v a r i a tion is n o t p r e s e n t in the l o w e r p e r c e n t i l e curves a n d a g r e e m e n t a m o n g the v a r i o u s studies on t h e t e n t h p e r c e n t i l e d i s t r i b u t i o n is g o o d ? T h i s is t r u e in p a r t because t h e r e is a l o w e r absolute limit to t h e birth weight, so t h a t the d a t a t e n d to cluster into a t i g h t e r group. M o r e i m p o r t a n t l y , in those studies
UNIVERSITY
OF COLORADO
CLASSIFICATION BY B I R T H W E I G H T AND
GRAMS
MEDICAL
CENTER
OF N E W B O R N S
AND
BY N E O N A T A L
GESTATIONAL MORTALITY
AGE
RISK
lllllllllllllll In HIS uunnnuunounnnn u n m u m mmmnu~nmmmmnmnmmmmn mmmmmmmnummmmmmmmwn~m,~,~ mnnnunnm mnunuununuumn~,~ im-- ===I mmnummmnmmnnunm~imsummmnunnunm mmulimmiiuw~auim,oH,=uBa nmmmmmmmmununnpmnmum mnnmu u n ~ m mnuunnumwn~ammmmmmma Fig. i~ltlli INN~IHi i~-a Jill IIIIIIIIIKI.~ BE il~'~E| IIIillll~i,~l El I.~il IIIII JlEI.~IIIIIIIII IEIIIIIIIIIIR
I--4 r~ 26 21 28 29 3y 3~ ~2 J3 3~ 3~ 36 31 38 3~ ~0 41 ~2 ~
~4 ~
~6
W E E K S OF G E S T A T I O N PRE.TERM
UNIVERSITY
I
OF COLORADO
CLASSIFICATION GRAMS
SY B t R T H W E ( G H T
AND
TERM
MEDICAL
I
POST.TERM
J
CENTER
OF NEWBORNS GESTATIONAL
AGE
Fig. 2
24
25
26 27 2B 29
3 0 31
32
33
WEEKS
'E-TERM
34 3 5 3 6
37
3 8 39 4 0
41
42 43
44
45 46
OF GESTATION
I,ERM I,O..,.M I
16 2
Battaglia and Lubchenco
The Journal o/ Pediatrics August 1967
that have reported neonatal and perinatal mortality rates, there has been good agreement among the studies for mortality rates in a given birth weight and gestationaI age group5 ~'4 All of these studies have confirmed the clinical impression that infants born with birth weights small for their gestational ages have lower neonatal mortality rates than do infants of the same weight born earlier in gestation but greater mortality rates than infants of the same gestational age who have appropriate birth weights. The tenth and ninetieth percentile groupings based upon both male and female infants from the study of Lubchenco and associates ~ have been used for the subdivisions by weight. All infants above the ninetieth percentile are referred to as Large for their Gestational Age, those below the tenth percentile as Small for their Gestational Age, and those between the tenth and ninetieth percentile as Appropriate for their Gestational Age. As pointed out by Battaglia and asso.ciates, 3 the choice of which population distribution is used in the subdivisions by weight would make little difference in the position of the tenth percentile, but does make a big difference in the position of the ninetieth percentile. The Colorado study was chosen for two reasons: first, it was one of the earliest studies giving a frequency distribution by birth weight and gestational age and thus is the one most familiar to pediatricians. Secondly, this study has the tightest distribution of appropriate for their gestational age infants at early gestational ages. It seemed worthwhile to incorporate "this tight distribution" in a classification proposed for detection of highrisk infants, since previous studies have shown that the neonatal mortality rate of large infants born early is higher by weight alone than is expected. NEONATAL
MORTALITY
RATES
The Neonatal Mortality Rate data of Erhardt, ~ have been adapted to the birth weight-gestational age chart. This is the largest study of mortality rates at given birth weights and gestational ages. Though it is not
ideal for such purposes, it is the best available at this time. Ideally, one would like more numerous Neonatal Mortality Rate zones with each zone encompassing a narrower mortality rate group. In addition, such mortality rates should be based upon local data and revised frequently (Figs. 1 and 2 contain the same birth weight-gestational age classification; one with and one without the superimposed mortality zones). Thus, the basic classification of nine newborn groups can be used as is, or with Erhardt's data, or with local Neonatal Mortality Rates substituted when indicated. NURSERY
PROCEDURE
At the time of admission to the nursery, the head nurse plots the infant's birth weight and gestationai age on the chart shown in Fig. 2, using the estimated age calculated by the house staff from the last day of menstrual period on the obstetrical chart. The color of the tape denotes the appropriate Neonatal Mortality Rate zone and the lettering, which of the nine gestational agebirth weight groups the infant falls into ( Table 1). All infants falling in a blue or red mortality zone, i.e., 25 per cent or greater risk of dying, should be admitted to a high-risk nursery. In addition, all infants who have any significant clinical problem, regardless of classification, are admitted to a high-risk nursery. The method described above provides a convenient means of defining Pre-Term, Term, and Post-Term infants, and the mortality risk makes possible a decision as to type of nursery care needed for an individual infant. The advantages of setting up such a routine on a nursery service are considerable. First, it ensures that all infants in a high Neonatal Mortality Rate group will be observed closely. Secondly, it makes it a great deal more convenient on house staff or attending staff rounds to identify small for their gestational age and large for their gestational age infants, particularly in separating small for their gestationaI age Term infants from appropriate for their gestational age PreTerm infants.
Volume 71
Number 2
Birth-weight and gestationaI-age classification 1 6 3
REFERENCES 1. Lubchenco, L. O., Hansman, C., Dressler, M., and Boyd, E.: Intrauterine growth as estimated from liveborn birth-weight data at 24 to 42 weeks of gestation, Pediatrics 32: 793, 1963. 2. Butler, N. R., and Bonham, D. G., editors: Perinatal mortality: The first report of the British perinatal mortality survey, London, 1963, E. & S. Livingstone, Ltd. 3. Battaglla, F. C., Frazier, T. M., and I-Iellegers, A. E.: Birth weight, gestational age, and pregnancy outcome, with special reference to highbirth-weight-low-gestational-age infant, Pediatrics 37: 717, 1966.
4. Ehrhardt, C. L., Joshi, G. B., Nelson, F. G., Kroll, B. H., and Weiner, L.: Influence of weight and gestation on perinatal and neonatal mortality by ethnic group, Am. J. Pub. Health 54: 1841, 1964. 5. Gruenwald, P.: Growth of the human fetus: I. Normal growth and its variation, Am. J. Obst. & Gynec. 94" 1112, 1966. 6. van den Berg, B. J., and Yerushalmy, J.: The relationship of the rate of intrauterine growth of infants of low birth weight to mortality, morbidity, and congenital anomalies, J. PEDIAT. 69: 531, 1966.
