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Growth of low-birth-weight infants
July, 1970 T h e Journal o[ P E D I A T R I C S
11
Gromh of lo v-birth- eigbt infants Growth in weight, length, and head eircum[erence was measured through the first year o[ li[e in three groups o[ low-birth-weight in[ants: very premature, moderately premature, and mature but severely undersized. Curves o[ growth for each group were compared to those considered normal for the [etus and newborn in[ant. When corrected [or gestationaI age, growth curves [or weight and length o[ the study groups paralleled but remained below the standard curves. Head size in the premature in[ants regained the standard curves; in the undergrown term in[ant, only part o[ the difference existing at birth was made up.
S. Gorham Babson, M.D. PORTLAND,
ORE.
L O N O I ' r U D I ~ A L studies of growth in Iow-birth-weight infants have been reported, in the main, on the basis of birth weight without regard to gestational age. In this study, particular attention is paid to grouping such infants on the basis of both birth weight and length of gestation. One purpose of the study is to,gompare growth in weight, length, and head circumference among three different groups of infants; these measurements for each group are also compared to those presumed representative for the average fetus and infant of corresponding gestational age. To visualize these comparisons, a graph was prepared to show curves of fetal growth in the three parameters for the last trimester of pregnancy and through the first year of life after From the Department o[ Pediatrics, University o[ Oregon Medical School. Address: 3181 S.W. Sam Jackson Park Road, Portland, Oregon 97201.
the equivalent age of "term ''~ has been reached. Another purpose of the study is to compare the composite curves of growth of the three groups from the time of birth with no correction for gestational age. SAMPLE Since 1962 all low-birth-weight infants admitted to the Premature Center of the University of Oregon Medical School have been measured longitudinally for weight, length, and head circumference. Three weight-gestation groups were selected for study. Group A : Very premature with weight appropriate for gestational age, gestation, 27 to 29 weeks; birth weight 0.95 to 1.30 Kg. Group B: Moderately premature with weight appropriate for gestational age, gestation, 31 to 33 weeks; birth weight, 1.40 to ~ " T e r m " represents approximately 40 weeks of age estimated from the first day of the last menstrual period, regardless o[ the time of birth.
Vol. 77, No. I, pp. 11-18
12
Babson
T h e Journal o[ Pediatrics July 1970
2.00 Kg. G r o u p C : Full-term, but severely underweight for gestational age, 38 weeks or more; birth weight less than 2.00 Kg. Additional criteria for inclusion were: ( 1 ) Caucasian, single born, with no obvious congenital abnormalities or fetal infection; (2) clinical evidence on examination of the infant at birth, supporting the calculation of
gestational age from the time of the last menstrual period; (3) daily determinations of weight and weekly measurements of length and h e a d circumference from one week of age until discharge from the hospital; (4) at least three complete measurements in the follow-up study clinic during the year following discharge from the hos-
- ovo:
. . . . . . .
2)
r
......
?
!i:
?i:ii
?
Fig. 1. A fetal infant growth graph derived from multiple sources which shows growth curves of weight, length, and head circumference from 26 weeks of gestational age through one year of life after "term" has been reached.
Table I. A composite of means and standard deviations for measurements of growth in weight, Fetus
28 wk. Weight (Kg.) Length (era.) Head (era.)
1.12 + 0.26 38.1 + 1.3 26.3 -+ 1.0
I
32 wk. 1.78 + 0.35 42.9 + 1.5 29.9 + 1.0
4
36 2,62 + 0.42 47.5 -+ 1.16 33.0 + 1.25
I
4o 3.40-+ 0.46 50.0 + 2.0 34.7 -'2 1.5
Volume 77 Number 1
Growth of low-birth-weight in[ants
pital; (5) no evidence of gross neurologic deficit or retardation through 18 months of age. T h e infants included in the study represent bias in favor of those who had a successful outcome and whose parents cooperated in the follow-up observations. Twelve infants met the qualifications for inclusion in Group C during the study period (1962 to 1965); accordingly, twelve infants were selected for Groups A and B. Only one infant in Group C was a male, but in Groups A and B infants were selected to achieve an equal ratio of sexes. Among the prematurely born infants (Groups A and B) the volume of formula given was 150 ml. per kilogram of body weight by the end of the second week of life in most instances; when this volume was reached, it was maintained until the infants weighed approximately 2200 Gm. T h e formulas used contained 80 calories per 100 ml. T h e infants received an average calorie intake of 115 per kilogram per day, and 3.2 Gm. per kilogram per day of protein, during the study period. Group C infants were fed in an unrestricted manner.
METHODS Weight was obtained from an automatic Toledo balance scale, accurate to 10 Gin. The babies were weighed prior to the morning feeding. Crown-heel measurements were made with the baby flat and both legs extended in a measuring device containing a built-in centimeter rule. H e a d circumference was reported at the largest occipitofrontal measurement obtained from two trials. Measurements were made weekly starting at seven days of age. Means and standard deviations were calculated from the mea-
surements of growth for the weekly periods during the nursery phase. Since measurements could not be made at precisely the same age for all infants after discharge from the hospital, derived measurements for appropriate interval~ of time were extrapolated from the curves of growth of each infant. This was accomplished by the use of an enlarged version of the growth graph (Fig. 1). Measurements for each parameter of growth were plotted on the vertical against the corrected age to tile nearest week on the horizontal. The best-fitting curve was drawn with the aid of an adjustable Dietzgen curve rule. The points at which this curve intersected with the time period of term, 3, 6, 9, and 12 months representing, respectively, 40, 53, 66, 79, and 92 weeks of postmenstrual age were taken as the calculated measurements for each infant at that age. Thus all infants had the same age reference calculated from the first day of the last menstrual period, representing the gestational plus the postnatal age. Means and standard deviations were calculated for each time period from the extrapolated measurements of each group. For estimation of fetal growth in weight, length, and head circumference, data were obtained from measurements reported in the literature for infants of known gestational age? -4 Data for postnatal growth were taken from longitudinal measurements of full-sized infants obtained from multiple sources 5-8 (Table I ) . Fig. 1 presents the mean curves of growth constructed from these data from 28 weeks of gestational age through one year of age after "term" has been reached. The stippled areas cover one standard deviation. Since infants who are
length, and head circumference for the fetus and infant, derived from multiple sources
_
3mo. 5.7 -- 0.7 ~9.9 *_ 2.5 ~0.3 • 1.6
I
6mo. 7.5 -+ 1.0 , ~ : ~ • 3.0 ~3.3 • ~.~
Infant p
13
9mo. 8.9 -+ 1.3 7~.~ *_ 3.2 45.3 _+ ~.8
f
,2mo. 10.0 -+ 1.5 75.0 • 3.5 ~ . 5 • 2.o
1 4 Babson
2"he Journal o[ Pediatrics July 1970
T a b l e I I . G r o u p A : 12 i n f a n t s . W e i g h t , l e n g t h , a n d h e a d c i r c u m f e r e n c e ( m e a n _+ 1 s t a n d a r d d e v i a t i o n ) f r o m 28 w e e k s o f g e s t a t i o n ( r a n g e 27 to 29) t o o n e y e a r of age after "term" has been reached
Age (wk. o[ "gestation") Birth Range Low 1 wk. 2 wk. 3 wk. 4 wk. 6 wk. 8 wk. 10 wk. "Term" 3 me. 6 me. 9 me. 12 me.
Weight (Kg.)
(28)
1.12 0.95 0.92 0.95 1.03 1.12 1.24 1.59 1.93 2.20 2.60 5.12 6.81 8.00 8.84
(29) (30) (31) (32) (34) (36) (38) (40)
Length (cm.)
-+ 0.12 - 1.35 + 0.12 -+ 0.11 -+ 0.16 + 0.17 + 0.17 + 0.25 +- 0.29 + 0.24 _+ 0.25 -+ 0.65 +- 1.00 + 1.20 +- 1.30
Head clrcum[erenee (cm.)
37.7 38.2 39.1 40.1 42.1 44.0
+- 1.2 + 1.4 -+ 1.5 -+ 1.3 "2- 1.7 + 1.7
25.6 26.3 27.2 28.2 30.4 32.4
-+ + -+ -+ -+ +
1.0 1.1 1.1 1.1 1.3 1.0
47.4 56.4 62.5 67.3 71.1
-+ + -+ + +-
34.8 40.4 43.5 45.2 46.3
+ -+ +++
0.8 0.9 0.9 0.9 1.1
1.5 2.3 2.4 2.6 2.8
T a b l e I I I . G r o u p B: 12 i n f a n t s . W e i g h t , l e n g t h , a n d h e a d c i r c u m f e r e n c e ( m e a n +_ 1 s t a n d a r d d e v i a t i o n ) f r o m 32 w e e k s of g e s t a t i o n ( r a n g e 31 to 33) t o o n e y e a r of age after "term" has been reached
Age (wk. o[ "'gestation") Birth Range Low 7 day 2 wk. 3 wk. 4 wk. 6 wk, "Term" 3 me. 6 me. 9 me. 12 me.
Welght (Kg.)
(32)
1.59 1.40 1.39 1.42 1.52 1.67 1.87 2.23 2.64 5.34 7.03 8.30 9.21
(33) (34) (35) (36) (38) (40)
Length (cm.)
+ 0.14 - 1.85 + 0.14 + 0.15 +- 0.16 + 0.18 -+ 0.21 +- 0.18 -+ 0.30 +- 0.66 + 0.91 --2 1.12 -+ 1.28
42.0 42.9 44.0 45.1 47.2 48.8 58.2 65.1 70.0 74.2
+ -+ -+ + +-+ -+ + -+ -+
1.1 1.0 1.3 1.2 1.1 1.3 1.8 2.2 2.4 3.6
Head clrcum[erence (cm.)
28.5 29.1 3O.2 31.2 33.2 34.5 40.2 43.4 45.0 46.0
++ ++ ++ -+ -+ -+ +
0.7 0.7 0.8 0.8 0.7 0.6 0.9 1.2 1.0 1.3
T a b l e I V . G r o u p C : 12 i n f a n t s . W e i g h t , l e n g t h , a n d h e a d c i r c u m f e r e n c e ( m e a n + 1 s t a n d a r d d e v i a t i o n ) f r o m 39 w e e k s o f g e s t a t i o n ( r a n g e 38 to 41) to o n e y e a r of life
Age Birth (39.3 wk.) Range Low 1 wk. (term) 2 wk. 3 me. 6 me. 9 me. 12 me.
I
Weight(Kg.) 1.66 1.32 1.58 1.68 1.90 4.18 5.80 6.91 7.67
+ 0.21 - 1.90 +- 0.20 + 0.22 -+ 0.25 +- 0.48 + 0.61 + 0.71 -+ 0.93
[
Length(cm.)
43.8 44.6 54.6 61.2 65.5 69.2
-+ + + -+
1.1 1.1 2.1 2.4 2.3 2.4
l Head cricum[eren.) ce(cm
30.6 31.6 37.8 41.2 43.2 44.4
++ -+ + +-
0.6 1.0 1.3 1.7 2.0 2.2
Volume 77 Number 1
Growth of low-birth-weight infants
15
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~ 2 ~5
............. ~:;N g!;i*
Fig. 2. Plotted on the fetal infant growth graph (Fig. 1) are the mean growth curves of three groups of low-blrth-weight infants: A, very premature and appropriate in size; B, moderately premature and appropriate in size; C, full term but severely undergrown. These curves are plotted against the gestational age for that group.
born prematurely do not have the reduction in growth expected of the fetus as term is approached, the curves have been smoothed through this usual transitional period. RESULTS
I n Tables II, I I I , and I V are given the mean and one standard deviation of growth in weight, length, and head circumference for each time period for the three groups of low-birth-weight infants. 9 Fig. 2 depicts the curves for growth with the means of each parameter of growth plotted against the gestational "age of that group. After a two-week lag, the curves for weight and length of the p r e m a t u r e l y b o r n infants (Groups A a~d B) parallel those constructed from measurements reported for
standard fetuses and infants throughout the first year of life. The curves are at a lower level, however, with the curve of the most immature group (A) being reduced the most. Head circumference, after a two-week lag, regains and follows the projected curve, suggesting a temporary acceleration in growth of the head. This is in contrast to growth in length. Growth in the undersized infants (Group C), after a lesser interruption following birth, also parallels the mean curves of fullsized infants, but at a level substantially below them as well-as those for the prematurely born groups. T h e curve for head growth in Group C gradually approaches that of full-sized in-
16
Babson
The Journal o[ Pediatrics July 1970
Table V. Increments of growth for three low-birth-weight groups and those for normal-sized infants in weight, length, and head circumference for the twelvemonth period after the equivalent of 40 weeks of gestation has been reached
Weight (Kg.) Length (cm.) Head circumference (cm.)
Normal sized
Group A: small, premature
6.55 25.0 11.8
6.24 23.7 11.5
rants. However, the significant disparity in head size from the normal-sized infant at birth is only partly reduced by the end of the first year. Fig. 3 presents the growth curves of the Groups A, B, and C with the individual measurements for each parameter plotted against postnatal age without correction for gestational age. The premature infants, Groups A and B, contrary to the findings shown in Fig. 2, appear to have an increased rate of growth in all parameters; the curves approach those for full-slzed infants. Table V presents the increments of growth for the three study groups and for full-sized babies during the first year of life after the equivalent of "term" has been reached. These increments of increase for the three growth parameters in all groups are approximately the same except for head circumference, for which a greater increase is shown in the undersized term infants. COMMENTS
The inability to measure these groups of infants at the same age period after discharge from the hospitaI created a problem. Cross-sectional values extrapolated from the curves derived from the longitudinal growth measurements of each infant were used. Although this method reduces the validity of the data reported, it was the only practical way for obtaining the average growth of these groups of infants. A predominance of girls is seen in the undersized groups of infants. This discrepancy may be explained by the smaller size of girls at term and the increase in perinatal deaths of males.
Group B: moderate, premature
6.57 25.4 11.5
Group C: undergrown, term
6.01 25.4 13.8
The parallelism in the curves of growth in weight and length when those for lowbirth-weight infants are corrected for differences in gestational age has been shown by I-Iepner9 in selected patients. None of the loss in growth experienced after birth by the premature infants or undergrowth in the fetal period by the undersized infants is apparently made up in the first year of life. The curves of growth in the prematurely born infants, when plotted from birth without correction for gestational age (Fig. 3), appear to approach the curves of full-sized infants. This apparent increased rate of growth corresponds to that seen in the fetal period, when growth is more rapid. The early and temporary increase in rate of increase in head circumference by premature infants allows these infants to a p p r o a c h and even to surpass the projected curve for fetal head growth at a corresponding gestational age. This apparent "catch-up" in head size appears to coincide with the unridging of the sutures. The exaggerated increase in head circumference in the small premature infant between one and two months of postnatal age can on occasion give the clinician the false impression of developing hydrocephalus. A head-length ratio of less than 75 militates against the diagnosis of hydrocephalus in the premature infant during the nursery period. That some increase in fluid about or in the brain occurs is suggested by an extension of the area of reflected light seen on transillumination of the skull. These changes in head size may be related to the well-known late edema of prematurity and to the increased subarachnoid and subduraI space in the preterm infant.
Volume 77
Growth o[ low-birth-weight in[ants
I7
Number 1
::6:N~: :: i
~ ' s ~ 71;::::
..............
;r ~?..............
)
F i g . 3, T h e g r o w t h c u r v e s f o r the t h r e e g r o u p s of l o w - b i r t h - w e i g h t i n f a n t s are c o r r e c t i o n for gestational age.
The head growth in the undergrown infants of term gestation does not show this early exaggerated increase in size. Yet during the first year head size increases at a faster rate than in either the normaT-'sized term or in premature infants when measured from an age equivalent to that of "term." An increase in the increment of head growth from birth to four years of age has been shown in a larger group of moderately under-sized infants at birth when compared to full-sized control infants? ~ Very little, if any, "preferential" head growth occurred in utero in our Group C infants. This is supported b y - t h e close comparison of their head-length ratio at one week of age (70 per cent) with that of normally sized term infants (68.5 per cent). Others 11-13 hav~also shown proportional re-
plotted without
duction in head and length in the neonate at birth who has suffered intrauterine growth retardation, presumably f r o m undernutrltion. Thus head size appears to be a poor correlate of gestafional age in the small-fordates infants. SUMMARY
AND CONCLUSIONS
A graph of growth is presented on which longitudinal measurements of weight, length, and head circumference for infants of varying gestational ages can be plotted against the period of time from 26 weeks of gestation to one year beyond the expected time of birth. Curves have been drawn to represent fetal and infant growth from means and standard deviations of growth data derived from multiple sources? -s Data on three parameters of growth are
18
Babson
presented a n d p l o t t e d for three groups of low-birth-weight infants t h r o u g h the first y e a r of life. T h e i n f a n t groups, 12 in each, are very p r e m a t u r e , m o d e r a t e l y p r e m a t u r e , a n d term, severely undersized. W h e n the composite curves of g r o w t h in the study groups a r e corrected for their differences in gestational age, the following observations can be m a d e for the study p e r i o d : (1) Curves for length a n d weight in these low-birth-welght infants p a r a l l e l b u t r e m a i n below the curves of g r o w t h considered n o r m a l for the fetus a n d infant, w i t h those of the undersized g r o u p of infants being r e d u c e d the most. (2) H e a d circumference in the groups of p r e m a t u r e infants, after a n initial lag, increases at an accelerated rate so t h a t their g r o w t h curves m a y a p p r o a c h or t e m p o r a r i l y surpass the expected m e a n curve for fetal growth. T h e r e a f t e r , h e a d circumference follows the expected p a t t e r n observed in n o r m a l infants. (3) I n the u n d e r g r o w n infant, h e a d circumference at birth is r e d u c e d p r o p o r t i o n ately to length. T h e curve for h e a d size a p p e a r s to a p p r o a c h t h a t seen in infants of n o r m a l size, b u t the difference existing at b i r t h is only p a r t l y reduced. C o m p a r i s o n s of g r o w t h curves for infants of different gestational ages, w h e n plotted on s t a n d a r d g r a p h s on w h i c h b i r t h is considered to be a t term, are n o t as m e a n i n g ful as when correction is m a d e for early birth. F r o m these d a t a it a p p e a r s t h a t little, if any, of the r e t a r d a t i o n in weight a n d length t h a t m a y be suffered in the fetal or n e o n a t a l p e r i o d is m a d e u p d u r i n g the first y e a r of life if the infant's age is corrected to term.
The Journal o[ Pediatrics July 1970
REFERENCES
1. Babson, S. G., and McKinnon, C. M.: Determination of gestational age in premature infants, J. Lancet 87: 174, 1967. 2. Lubchenco, L. O., Hansman, M., and Boyd, E.: The weight, height, and head circumference of living infants born after 24 weeks of gestational age and graphed as percentiles, Pediatrics 37: 403, 1966. 3. Usher, R., and McLean, F.: Intrauterine growth of live-born Caucasian infants at sea level: Standards obtained from measurements of infants born between 25 and 44 weeks of gestation, J. P~DIAT. 74: 901, 1969. 4. Babson, S. G., Behrman, R. E., and Lessel, R.: Fetal growth-live-born birth weights for gestational age of white middle class infants, Pediatrics. In press. 5. Vickers, V. S., and Stuart, H. C.: Anthropometry in the pediatrician's office: Norms for selected body measurements based on studies of children of North European stock, J. PEDIAT. 22: 155, 1943. 6. Meredith, H. V.: Physical growth from birth to two years. II. Head circumference, Part I: A review and synthesis on North American research on groups of infants, Child Develop. 17: 1, 1946. 7. Simmons, K.: Growth and development, monograph, Soc. Research Child Develop. IX: I, Washington, D. C., 1944, National Research Council. 8. Nellhaus, G.: Head circumference from birth to eighteen years, Pediatrics 41: 106, 1968. 9. Hepner, R.: In Gruenwald, P., Dawkins, M., and Hepner, R.: Panel discussion--chronic deprivation of the fetus, Sinai Hosp. J. 11: 51, 1963. 10. Babson, S. G., and Kangas, J.: Preschool intelligence of undersized term infants, Amer. J. Dis. Child. 117: 553, 1969. 11. Lubchenco, L. O., Hansman, C., and Bachstrom, L.: In Janxis, J. H. P., Visser, H. K. A., and Troelstra, J. A., editors: Factors influencing fetal growth. Aspects of prematurity and dysmaturity, Springfield, Ill., 1968, Charles C Thomas, Publisher. 12. Usher, R., McLean, F., and Scott, K. E.: Judgement of fetal age, Pedlar, Clin. N. Amer. 13: 835, 1966. 13. 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.
11
Gromh of lo v-birth- eigbt infants Growth in weight, length, and head eircum[erence was measured through the first year o[ li[e in three groups o[ low-birth-weight in[ants: very premature, moderately premature, and mature but severely undersized. Curves o[ growth for each group were compared to those considered normal for the [etus and newborn in[ant. When corrected [or gestationaI age, growth curves [or weight and length o[ the study groups paralleled but remained below the standard curves. Head size in the premature in[ants regained the standard curves; in the undergrown term in[ant, only part o[ the difference existing at birth was made up.
S. Gorham Babson, M.D. PORTLAND,
ORE.
L O N O I ' r U D I ~ A L studies of growth in Iow-birth-weight infants have been reported, in the main, on the basis of birth weight without regard to gestational age. In this study, particular attention is paid to grouping such infants on the basis of both birth weight and length of gestation. One purpose of the study is to,gompare growth in weight, length, and head circumference among three different groups of infants; these measurements for each group are also compared to those presumed representative for the average fetus and infant of corresponding gestational age. To visualize these comparisons, a graph was prepared to show curves of fetal growth in the three parameters for the last trimester of pregnancy and through the first year of life after From the Department o[ Pediatrics, University o[ Oregon Medical School. Address: 3181 S.W. Sam Jackson Park Road, Portland, Oregon 97201.
the equivalent age of "term ''~ has been reached. Another purpose of the study is to compare the composite curves of growth of the three groups from the time of birth with no correction for gestational age. SAMPLE Since 1962 all low-birth-weight infants admitted to the Premature Center of the University of Oregon Medical School have been measured longitudinally for weight, length, and head circumference. Three weight-gestation groups were selected for study. Group A : Very premature with weight appropriate for gestational age, gestation, 27 to 29 weeks; birth weight 0.95 to 1.30 Kg. Group B: Moderately premature with weight appropriate for gestational age, gestation, 31 to 33 weeks; birth weight, 1.40 to ~ " T e r m " represents approximately 40 weeks of age estimated from the first day of the last menstrual period, regardless o[ the time of birth.
Vol. 77, No. I, pp. 11-18
12
Babson
T h e Journal o[ Pediatrics July 1970
2.00 Kg. G r o u p C : Full-term, but severely underweight for gestational age, 38 weeks or more; birth weight less than 2.00 Kg. Additional criteria for inclusion were: ( 1 ) Caucasian, single born, with no obvious congenital abnormalities or fetal infection; (2) clinical evidence on examination of the infant at birth, supporting the calculation of
gestational age from the time of the last menstrual period; (3) daily determinations of weight and weekly measurements of length and h e a d circumference from one week of age until discharge from the hospital; (4) at least three complete measurements in the follow-up study clinic during the year following discharge from the hos-
- ovo:
. . . . . . .
2)
r
......
?
!i:
?i:ii
?
Fig. 1. A fetal infant growth graph derived from multiple sources which shows growth curves of weight, length, and head circumference from 26 weeks of gestational age through one year of life after "term" has been reached.
Table I. A composite of means and standard deviations for measurements of growth in weight, Fetus
28 wk. Weight (Kg.) Length (era.) Head (era.)
1.12 + 0.26 38.1 + 1.3 26.3 -+ 1.0
I
32 wk. 1.78 + 0.35 42.9 + 1.5 29.9 + 1.0
4
36 2,62 + 0.42 47.5 -+ 1.16 33.0 + 1.25
I
4o 3.40-+ 0.46 50.0 + 2.0 34.7 -'2 1.5
Volume 77 Number 1
Growth of low-birth-weight in[ants
pital; (5) no evidence of gross neurologic deficit or retardation through 18 months of age. T h e infants included in the study represent bias in favor of those who had a successful outcome and whose parents cooperated in the follow-up observations. Twelve infants met the qualifications for inclusion in Group C during the study period (1962 to 1965); accordingly, twelve infants were selected for Groups A and B. Only one infant in Group C was a male, but in Groups A and B infants were selected to achieve an equal ratio of sexes. Among the prematurely born infants (Groups A and B) the volume of formula given was 150 ml. per kilogram of body weight by the end of the second week of life in most instances; when this volume was reached, it was maintained until the infants weighed approximately 2200 Gm. T h e formulas used contained 80 calories per 100 ml. T h e infants received an average calorie intake of 115 per kilogram per day, and 3.2 Gm. per kilogram per day of protein, during the study period. Group C infants were fed in an unrestricted manner.
METHODS Weight was obtained from an automatic Toledo balance scale, accurate to 10 Gin. The babies were weighed prior to the morning feeding. Crown-heel measurements were made with the baby flat and both legs extended in a measuring device containing a built-in centimeter rule. H e a d circumference was reported at the largest occipitofrontal measurement obtained from two trials. Measurements were made weekly starting at seven days of age. Means and standard deviations were calculated from the mea-
surements of growth for the weekly periods during the nursery phase. Since measurements could not be made at precisely the same age for all infants after discharge from the hospital, derived measurements for appropriate interval~ of time were extrapolated from the curves of growth of each infant. This was accomplished by the use of an enlarged version of the growth graph (Fig. 1). Measurements for each parameter of growth were plotted on the vertical against the corrected age to tile nearest week on the horizontal. The best-fitting curve was drawn with the aid of an adjustable Dietzgen curve rule. The points at which this curve intersected with the time period of term, 3, 6, 9, and 12 months representing, respectively, 40, 53, 66, 79, and 92 weeks of postmenstrual age were taken as the calculated measurements for each infant at that age. Thus all infants had the same age reference calculated from the first day of the last menstrual period, representing the gestational plus the postnatal age. Means and standard deviations were calculated for each time period from the extrapolated measurements of each group. For estimation of fetal growth in weight, length, and head circumference, data were obtained from measurements reported in the literature for infants of known gestational age? -4 Data for postnatal growth were taken from longitudinal measurements of full-sized infants obtained from multiple sources 5-8 (Table I ) . Fig. 1 presents the mean curves of growth constructed from these data from 28 weeks of gestational age through one year of age after "term" has been reached. The stippled areas cover one standard deviation. Since infants who are
length, and head circumference for the fetus and infant, derived from multiple sources
_
3mo. 5.7 -- 0.7 ~9.9 *_ 2.5 ~0.3 • 1.6
I
6mo. 7.5 -+ 1.0 , ~ : ~ • 3.0 ~3.3 • ~.~
Infant p
13
9mo. 8.9 -+ 1.3 7~.~ *_ 3.2 45.3 _+ ~.8
f
,2mo. 10.0 -+ 1.5 75.0 • 3.5 ~ . 5 • 2.o
1 4 Babson
2"he Journal o[ Pediatrics July 1970
T a b l e I I . G r o u p A : 12 i n f a n t s . W e i g h t , l e n g t h , a n d h e a d c i r c u m f e r e n c e ( m e a n _+ 1 s t a n d a r d d e v i a t i o n ) f r o m 28 w e e k s o f g e s t a t i o n ( r a n g e 27 to 29) t o o n e y e a r of age after "term" has been reached
Age (wk. o[ "gestation") Birth Range Low 1 wk. 2 wk. 3 wk. 4 wk. 6 wk. 8 wk. 10 wk. "Term" 3 me. 6 me. 9 me. 12 me.
Weight (Kg.)
(28)
1.12 0.95 0.92 0.95 1.03 1.12 1.24 1.59 1.93 2.20 2.60 5.12 6.81 8.00 8.84
(29) (30) (31) (32) (34) (36) (38) (40)
Length (cm.)
-+ 0.12 - 1.35 + 0.12 -+ 0.11 -+ 0.16 + 0.17 + 0.17 + 0.25 +- 0.29 + 0.24 _+ 0.25 -+ 0.65 +- 1.00 + 1.20 +- 1.30
Head clrcum[erenee (cm.)
37.7 38.2 39.1 40.1 42.1 44.0
+- 1.2 + 1.4 -+ 1.5 -+ 1.3 "2- 1.7 + 1.7
25.6 26.3 27.2 28.2 30.4 32.4
-+ + -+ -+ -+ +
1.0 1.1 1.1 1.1 1.3 1.0
47.4 56.4 62.5 67.3 71.1
-+ + -+ + +-
34.8 40.4 43.5 45.2 46.3
+ -+ +++
0.8 0.9 0.9 0.9 1.1
1.5 2.3 2.4 2.6 2.8
T a b l e I I I . G r o u p B: 12 i n f a n t s . W e i g h t , l e n g t h , a n d h e a d c i r c u m f e r e n c e ( m e a n +_ 1 s t a n d a r d d e v i a t i o n ) f r o m 32 w e e k s of g e s t a t i o n ( r a n g e 31 to 33) t o o n e y e a r of age after "term" has been reached
Age (wk. o[ "'gestation") Birth Range Low 7 day 2 wk. 3 wk. 4 wk. 6 wk, "Term" 3 me. 6 me. 9 me. 12 me.
Welght (Kg.)
(32)
1.59 1.40 1.39 1.42 1.52 1.67 1.87 2.23 2.64 5.34 7.03 8.30 9.21
(33) (34) (35) (36) (38) (40)
Length (cm.)
+ 0.14 - 1.85 + 0.14 + 0.15 +- 0.16 + 0.18 -+ 0.21 +- 0.18 -+ 0.30 +- 0.66 + 0.91 --2 1.12 -+ 1.28
42.0 42.9 44.0 45.1 47.2 48.8 58.2 65.1 70.0 74.2
+ -+ -+ + +-+ -+ + -+ -+
1.1 1.0 1.3 1.2 1.1 1.3 1.8 2.2 2.4 3.6
Head clrcum[erence (cm.)
28.5 29.1 3O.2 31.2 33.2 34.5 40.2 43.4 45.0 46.0
++ ++ ++ -+ -+ -+ +
0.7 0.7 0.8 0.8 0.7 0.6 0.9 1.2 1.0 1.3
T a b l e I V . G r o u p C : 12 i n f a n t s . W e i g h t , l e n g t h , a n d h e a d c i r c u m f e r e n c e ( m e a n + 1 s t a n d a r d d e v i a t i o n ) f r o m 39 w e e k s o f g e s t a t i o n ( r a n g e 38 to 41) to o n e y e a r of life
Age Birth (39.3 wk.) Range Low 1 wk. (term) 2 wk. 3 me. 6 me. 9 me. 12 me.
I
Weight(Kg.) 1.66 1.32 1.58 1.68 1.90 4.18 5.80 6.91 7.67
+ 0.21 - 1.90 +- 0.20 + 0.22 -+ 0.25 +- 0.48 + 0.61 + 0.71 -+ 0.93
[
Length(cm.)
43.8 44.6 54.6 61.2 65.5 69.2
-+ + + -+
1.1 1.1 2.1 2.4 2.3 2.4
l Head cricum[eren.) ce(cm
30.6 31.6 37.8 41.2 43.2 44.4
++ -+ + +-
0.6 1.0 1.3 1.7 2.0 2.2
Volume 77 Number 1
Growth of low-birth-weight infants
15
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~ 2 ~5
............. ~:;N g!;i*
Fig. 2. Plotted on the fetal infant growth graph (Fig. 1) are the mean growth curves of three groups of low-blrth-weight infants: A, very premature and appropriate in size; B, moderately premature and appropriate in size; C, full term but severely undergrown. These curves are plotted against the gestational age for that group.
born prematurely do not have the reduction in growth expected of the fetus as term is approached, the curves have been smoothed through this usual transitional period. RESULTS
I n Tables II, I I I , and I V are given the mean and one standard deviation of growth in weight, length, and head circumference for each time period for the three groups of low-birth-weight infants. 9 Fig. 2 depicts the curves for growth with the means of each parameter of growth plotted against the gestational "age of that group. After a two-week lag, the curves for weight and length of the p r e m a t u r e l y b o r n infants (Groups A a~d B) parallel those constructed from measurements reported for
standard fetuses and infants throughout the first year of life. The curves are at a lower level, however, with the curve of the most immature group (A) being reduced the most. Head circumference, after a two-week lag, regains and follows the projected curve, suggesting a temporary acceleration in growth of the head. This is in contrast to growth in length. Growth in the undersized infants (Group C), after a lesser interruption following birth, also parallels the mean curves of fullsized infants, but at a level substantially below them as well-as those for the prematurely born groups. T h e curve for head growth in Group C gradually approaches that of full-sized in-
16
Babson
The Journal o[ Pediatrics July 1970
Table V. Increments of growth for three low-birth-weight groups and those for normal-sized infants in weight, length, and head circumference for the twelvemonth period after the equivalent of 40 weeks of gestation has been reached
Weight (Kg.) Length (cm.) Head circumference (cm.)
Normal sized
Group A: small, premature
6.55 25.0 11.8
6.24 23.7 11.5
rants. However, the significant disparity in head size from the normal-sized infant at birth is only partly reduced by the end of the first year. Fig. 3 presents the growth curves of the Groups A, B, and C with the individual measurements for each parameter plotted against postnatal age without correction for gestational age. The premature infants, Groups A and B, contrary to the findings shown in Fig. 2, appear to have an increased rate of growth in all parameters; the curves approach those for full-slzed infants. Table V presents the increments of growth for the three study groups and for full-sized babies during the first year of life after the equivalent of "term" has been reached. These increments of increase for the three growth parameters in all groups are approximately the same except for head circumference, for which a greater increase is shown in the undersized term infants. COMMENTS
The inability to measure these groups of infants at the same age period after discharge from the hospitaI created a problem. Cross-sectional values extrapolated from the curves derived from the longitudinal growth measurements of each infant were used. Although this method reduces the validity of the data reported, it was the only practical way for obtaining the average growth of these groups of infants. A predominance of girls is seen in the undersized groups of infants. This discrepancy may be explained by the smaller size of girls at term and the increase in perinatal deaths of males.
Group B: moderate, premature
6.57 25.4 11.5
Group C: undergrown, term
6.01 25.4 13.8
The parallelism in the curves of growth in weight and length when those for lowbirth-weight infants are corrected for differences in gestational age has been shown by I-Iepner9 in selected patients. None of the loss in growth experienced after birth by the premature infants or undergrowth in the fetal period by the undersized infants is apparently made up in the first year of life. The curves of growth in the prematurely born infants, when plotted from birth without correction for gestational age (Fig. 3), appear to approach the curves of full-sized infants. This apparent increased rate of growth corresponds to that seen in the fetal period, when growth is more rapid. The early and temporary increase in rate of increase in head circumference by premature infants allows these infants to a p p r o a c h and even to surpass the projected curve for fetal head growth at a corresponding gestational age. This apparent "catch-up" in head size appears to coincide with the unridging of the sutures. The exaggerated increase in head circumference in the small premature infant between one and two months of postnatal age can on occasion give the clinician the false impression of developing hydrocephalus. A head-length ratio of less than 75 militates against the diagnosis of hydrocephalus in the premature infant during the nursery period. That some increase in fluid about or in the brain occurs is suggested by an extension of the area of reflected light seen on transillumination of the skull. These changes in head size may be related to the well-known late edema of prematurity and to the increased subarachnoid and subduraI space in the preterm infant.
Volume 77
Growth o[ low-birth-weight in[ants
I7
Number 1
::6:N~: :: i
~ ' s ~ 71;::::
..............
;r ~?..............
)
F i g . 3, T h e g r o w t h c u r v e s f o r the t h r e e g r o u p s of l o w - b i r t h - w e i g h t i n f a n t s are c o r r e c t i o n for gestational age.
The head growth in the undergrown infants of term gestation does not show this early exaggerated increase in size. Yet during the first year head size increases at a faster rate than in either the normaT-'sized term or in premature infants when measured from an age equivalent to that of "term." An increase in the increment of head growth from birth to four years of age has been shown in a larger group of moderately under-sized infants at birth when compared to full-sized control infants? ~ Very little, if any, "preferential" head growth occurred in utero in our Group C infants. This is supported b y - t h e close comparison of their head-length ratio at one week of age (70 per cent) with that of normally sized term infants (68.5 per cent). Others 11-13 hav~also shown proportional re-
plotted without
duction in head and length in the neonate at birth who has suffered intrauterine growth retardation, presumably f r o m undernutrltion. Thus head size appears to be a poor correlate of gestafional age in the small-fordates infants. SUMMARY
AND CONCLUSIONS
A graph of growth is presented on which longitudinal measurements of weight, length, and head circumference for infants of varying gestational ages can be plotted against the period of time from 26 weeks of gestation to one year beyond the expected time of birth. Curves have been drawn to represent fetal and infant growth from means and standard deviations of growth data derived from multiple sources? -s Data on three parameters of growth are
18
Babson
presented a n d p l o t t e d for three groups of low-birth-weight infants t h r o u g h the first y e a r of life. T h e i n f a n t groups, 12 in each, are very p r e m a t u r e , m o d e r a t e l y p r e m a t u r e , a n d term, severely undersized. W h e n the composite curves of g r o w t h in the study groups a r e corrected for their differences in gestational age, the following observations can be m a d e for the study p e r i o d : (1) Curves for length a n d weight in these low-birth-welght infants p a r a l l e l b u t r e m a i n below the curves of g r o w t h considered n o r m a l for the fetus a n d infant, w i t h those of the undersized g r o u p of infants being r e d u c e d the most. (2) H e a d circumference in the groups of p r e m a t u r e infants, after a n initial lag, increases at an accelerated rate so t h a t their g r o w t h curves m a y a p p r o a c h or t e m p o r a r i l y surpass the expected m e a n curve for fetal growth. T h e r e a f t e r , h e a d circumference follows the expected p a t t e r n observed in n o r m a l infants. (3) I n the u n d e r g r o w n infant, h e a d circumference at birth is r e d u c e d p r o p o r t i o n ately to length. T h e curve for h e a d size a p p e a r s to a p p r o a c h t h a t seen in infants of n o r m a l size, b u t the difference existing at b i r t h is only p a r t l y reduced. C o m p a r i s o n s of g r o w t h curves for infants of different gestational ages, w h e n plotted on s t a n d a r d g r a p h s on w h i c h b i r t h is considered to be a t term, are n o t as m e a n i n g ful as when correction is m a d e for early birth. F r o m these d a t a it a p p e a r s t h a t little, if any, of the r e t a r d a t i o n in weight a n d length t h a t m a y be suffered in the fetal or n e o n a t a l p e r i o d is m a d e u p d u r i n g the first y e a r of life if the infant's age is corrected to term.
The Journal o[ Pediatrics July 1970
REFERENCES
1. Babson, S. G., and McKinnon, C. M.: Determination of gestational age in premature infants, J. Lancet 87: 174, 1967. 2. Lubchenco, L. O., Hansman, M., and Boyd, E.: The weight, height, and head circumference of living infants born after 24 weeks of gestational age and graphed as percentiles, Pediatrics 37: 403, 1966. 3. Usher, R., and McLean, F.: Intrauterine growth of live-born Caucasian infants at sea level: Standards obtained from measurements of infants born between 25 and 44 weeks of gestation, J. P~DIAT. 74: 901, 1969. 4. Babson, S. G., Behrman, R. E., and Lessel, R.: Fetal growth-live-born birth weights for gestational age of white middle class infants, Pediatrics. In press. 5. Vickers, V. S., and Stuart, H. C.: Anthropometry in the pediatrician's office: Norms for selected body measurements based on studies of children of North European stock, J. PEDIAT. 22: 155, 1943. 6. Meredith, H. V.: Physical growth from birth to two years. II. Head circumference, Part I: A review and synthesis on North American research on groups of infants, Child Develop. 17: 1, 1946. 7. Simmons, K.: Growth and development, monograph, Soc. Research Child Develop. IX: I, Washington, D. C., 1944, National Research Council. 8. Nellhaus, G.: Head circumference from birth to eighteen years, Pediatrics 41: 106, 1968. 9. Hepner, R.: In Gruenwald, P., Dawkins, M., and Hepner, R.: Panel discussion--chronic deprivation of the fetus, Sinai Hosp. J. 11: 51, 1963. 10. Babson, S. G., and Kangas, J.: Preschool intelligence of undersized term infants, Amer. J. Dis. Child. 117: 553, 1969. 11. Lubchenco, L. O., Hansman, C., and Bachstrom, L.: In Janxis, J. H. P., Visser, H. K. A., and Troelstra, J. A., editors: Factors influencing fetal growth. Aspects of prematurity and dysmaturity, Springfield, Ill., 1968, Charles C Thomas, Publisher. 12. Usher, R., McLean, F., and Scott, K. E.: Judgement of fetal age, Pedlar, Clin. N. Amer. 13: 835, 1966. 13. 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.