Growth of Breast‑fed and Bottle‑fed Infants From Birth to 20 Months
著者 YONEYAMA Kyoko, NAGATA Hisanori journal or
publication title
奈良教育大学紀要. 自然科学
volume 43
number 2
page range 25‑35
year 1994‑11‑25
URL http://hdl.handle.net/10105/1644
Growth of Breast‑fed and Bottle‑fed Infants From Birth to 20 Months
Kyoko Yoneyama
(Department of Child Health and Care, Nara University of Education, Nara 630, Ja如n) and
Hisanori Nagata
(Faculty of Food and Nutritional Science, Mukogawa Women's University, Nishinomiya 663, Japan) (Received April 28, 1994)
Abstract
Longitudinal data for weight and length from birth to the 20th month of age obtained from 318 healthy infants were analyzed in relation to type of feeding during infancy (brast‑ or bottle‑fed). Differences in the growth patterns of infants according to the type of feeding were confirmed, breast‑fed infants tending to be lighter in weight than bottle‑fed infants. However, our analyses of the infants'growth patterns suggest that the differences in mean weight be‑
tween breast‑ and bottle‑fed infants may be due at least in part to over feeding of bottle‑fed in‑
fants. Thus, it is advisable that the standard growth curve for breast‑fed infants be based on observations of the growth of a large number of infants who are fed on breast milk only.
Introduction
It is indisputable that human milk is unique and is the most preferable first food for in‑
1‑9)
fants. However, various studies have indicated that breast‑fed infants tend to be smaller or to weigh less than bottle‑fed infants. There is no general agreement on whether or not this difference is due to the over feeding of bottle‑fed infants ; however, there is no doubt that when the mother's milk is insufficient, the growth of the breast‑fed infant would be retarded without the addition of powdered milk or some other supplement. Once powdered milk is in‑
troduced, however, most infants seem to prefer it to mothers'milk; decreased intake of mother s milk may not be desirable for infants, since the milk still contains relatively high
levels of total proteins and immunoglobulin A at 6 or 8th months after delivery10)
An ideal or standard growth curve for breast‑fed infants will be necessary for the early detection of growth retardation or to convince mothers to continue breast‑feeding without fear of growth retardation. Besides, growth curves of individual infants may differ. These in‑
dividual differences of growth curve will obscure differences of growth curves between breast‑ and bottle‑fed infants and make the evaluation of the growth of individual breast‑fed infants more difficult.
In the present study, growth of infants has been observed longitudinally concentrating
25
the attention on the difference between breast‑ and bottle‑ fed infants.
Materials and Methods
1. Subjects and Anthropometry.
Our data were obtained from an unselected population of 333 20‑month‑old infants (175 boys, 158 girls) who received health examinations at a health center in Nara, medium size city in Japan between February and May, 1991. All infants were Japanese born as singletons at fulトterm (37 weeks and more gestation). They all weighed more than 2500g at birth, and their mothers'pregnancies and deliveries were uneventful. In this health center, the general health and growth status of infants is examined at 1, 3, 6, 9, 12 and 20 months of age, with some infants being examined at 4, 7 and 10 months instead of at 3, 6, and 9 months, respec‑
tively. In our study, if the weights and lengths of infants were not measured at the desig‑
、lい
nated month, these values were interpolated by fitting the cubic spline function for each in‑
dividual.
Each infant's weight and length from birth to 12 months of age were obtained from the maternal and child health handbook. Naked weight was measured using standardized scales accurate to lOg, and length was measured by laying infants supine on a standardized length board accurate to 0.1 cm. All measurements were carried out by trained nurses. As most in‑
fants were examined at each designated month with a maximum variation of +7 days after that month, no correction for possible growth during the extra days was made. Only infants who had at least five measurements of weight and length (including those made at birth), and who had not missed two consecutive measurements, were included in the study.
2. Classification of feeding method and other related information.
Types of feeding during infancy were identified in interviews with mothers and were classified into three groups : (A) Breast Group : exclusively breast‑fed more than 6 months : no other source of milk, (B) Mixed Group : partially breast‑fed ; amount of mother's milk ing‑
estとd being greater than that of bottled milk, or almost equal amounts of breast and bottled milk, and (C) Bottle Group : bottled milk only or mainly bottled milk ; the amount of bottled milk being greater than that of mother's milk. Solid foods were given ad libitum, in addition to milk, in all groups. Information on the age of complete weaning from mother's milk, the age when solid food was initially given, the infant's birth order in the family, the gestation period, any history of illness of the infant, whether they attended a nursery school, the age of the mother and the weight and height of the parents was also elicited by interview. The pa‑
rent s socio‑economic and educational levels were not examined.
3. Analysis
The mean weight and length at birth and at each designated month, and the mean in‑
crease of weight and length during three month periods were calculated for all three groups.
The significance of the differences of these mean values among the groups were tested by analysis of variance. The weight and length of each infant at each designated month was further categorized into eight by the 3rd, 10th, 25th, 50th, 75th, 90th and 97th percentiles of weights and lengths by sex ; these calculations were performed for all subjects in this study, and the frequency distributions of the weight and length at each month and changes in the categorized weight and length from birth to the 3rd month, the 3rd to the 6th month, the 6th to the 12th month, and the 12th to the 20th month were compared in the breast and bottle groups. The significance of the differences in these frequency distributions between the two groups was tested by Kormogorov‑Smirnov statistics.
To examine whether the type of feeding had any effect on the infants weight or length at 12 and 20 months, multiple regression analyses were performed for boys and girls separately by the stepwise method. The independent variables were : birth weight and length, birth order in the family, weeks of gestation, parents'weights and heights, feeding type, age of complete weaning from mother's milk, age when solid food was initially given and whether the child attended a nursery school. For birth order (first or after the first) and attendance at nursery school, dummy variables with values of 1 and 0 were used ; for feeding type, two such dummy variables were used.
The SPSSx package was used for all statistical analyses.
Results
Data for 165 boys and 153 girls were available for analysis. The numbers of infants in the breast, bottle, and mixed groups were 112 [48 boys (29.1%), 64 girls (41.8%)], 133 [73 boys (44.2%), 60 girls (39.2%)], and 73 [44 boys (26.7%), 29 girls (19.0%)], respectively.
The percentage of breast‑fed girls was similar to the national figure in Japan, while it was a little less in boys. The time of initial solid food ingestion ranged from 3 to 7 months; the mean values were similar among the three feeding groups (5.1, 4.7, and 4.5 months in the breast, mixed, and bottle groups, respectively). The age of complete weaning from mother's milk was more than 7 months for all infants in the breast group; the mean ages were ll.7, 4.1, and 2.0 months in the breast, mixed, and bottle groups, respectively. The differences among the three feeding groups were significant by analysis of variance. The percentage of infants who were the eldest of the siblings was 45.9%, 46.6%, and 55.2%; the mean gesta‑
tion periods were 39.3, 39.4 and 39.3 weeks; and the mean ages of the mothers were 26.8,
27.1, and 26.9 years for breast, mixed and bottle groups, respectively. Thirty‑nine infants
attended nursery schools ; 21 0f these infants were in the bottle group. Many infants in all
feeding groups experienced illnesses, but most of them were minor infections, as colds, di‑
Table 1. Means and standard deviations of weight and length by feeding type.
Weight (g)
Boys Girls Age Bre (n ‑48)Mix (n ‑44)Bot (n ‑73) Bre (n ‑64)Mix (n ‑29)Bot (n ‑60)
Month M SD M SD M SD F t M SD M SD M SD F
3153 301 4450 436 6650 846 8126 827 8973 1122 9651 1040
3247 345 4494 414 6847 750 8472 814 9338 827 9991 935 20 11020 1161 11330 959
3215 378 0.88 0.8 4522 470 0.37 0.6 6712 665 0.84 0.3 762 2.18 1.1 9212 1.79 1.2 9932 1069 1.53 1.4
3106 310 4186 369 6268 690 7645 777 8276 1042 9059 907
3190 351 1230 382 6124 615 7660 674 8607 688 9250 799
3166 331 0.85 1.1 4327 456 1.8 6322 641 0.98 0.6 7860 751 1.45 1.6
5.20**3.1**
9538 4.45* 2.9**
11296 1140 1.15 1.3 10311 899 10600 715 10934 972 7.29**3.7**
Length (cm)
Boys Girls
Age Bre (n ‑44)Mix (n ‑43)Bot (n ‑71) Bre (n ‑63)Mix (n ‑28)Bot (n ‑59) Month M SD M SD M SD F t M SD M SD M SD
0 49.5 2.3 50.3 2.0 50.1 1.9 2.01 1.5 49.3 1.7 49.2 1.7 49.6 1.6 0.52 0.9 53.7 2.4 54.5 2.0 54.6 2.4 2.97 2.5* 53.3 2.0 53.5 1.8 54.2 2.4 2.74 2.2*
61.7 2.9 62.3 2.5 62.1 2.6 0.49 0.7 60.7 2.3 0.9 2.1 61.4 2.4 1.41 1.6 67.7 2.2 8.1 2.8 8.3 2.0 1.14 1.6 66.2 1.9 66.4 2.1 67.1 2.3 2.75 2.3*
71.6 2.5 72.3 2.8 72.7 2.7 2.40 2.3* 70.6 2.4 70.4 2.2 71.0 2.4 0.83 1.0 12 75.8 2.9 76.5 3.2 76.7 3.2 1.43 1.4 75.0 3.3 74.6 2.7 74.8 3.3 0.19 0.4 20 82.0 2.8 82.8 2.7 83.0 3.0 1.54 1.7 80.9 2.4 81.0 1.9 .9 2.9 2.47 1.8
Bre = exclusively Breast‑fed, Mix = Mixed breast‑ and bottle‑fed, Bot = mainly Bottle‑fed, F : F‑
testamongthethreegroups,t: t‑test between Bre and Bot * : P<0.05, ** : P<0.01
m : numbers of subjects
arrhea, or eczema. Morbidity rates of these diseases were generally similar among the three
groups.
Table 1 shows the mean values and standard deviations of weights and lengths for the three feeding groups. The growth curves of weight and length for the mixed group appeared to be similar to those of the bottle group for boys and to run between the two groups for girls. Because our interest was focused predominantly on the differences in growth curves according to feeding type, we compared study results only in the breast and bottle groups.
The differences in mean weight between these two groups were relatively small until four
months of age ; however, the differences increased thereafter, and the differences of mean
weight in girls from 9 to 20 months of age were significant. The mean weight of the breast
Table2. Means and standard deviations of gains in weight and length in breast‑ and bottle‑fed groups.
Weight gain (g) Length gain (cm)
Feeding Boys Girls Boys Girlsmonths Group M SD t M SD t M SD t M SD
0‑3 Bre 3497 749 0.00 3161 547 0.05 12.2 3.3 0.54 11.4 2.0 0.75 Bot 3497 627 3156 575 11.9 2.5 11.7 2.3 3‑6 Bre 1477 676 0.90 1377 533 1.76 6.0 2.0 0.80 5.5 1.8 0.56
Bot 1578 478 1538 485 6.2 2.0 5.7 2.1 6‑9 Bre 847 648 0.48 755 380 2.65** 3.9 1.8 1.23 4.2 1.8 0.85
Bot 922 422 950 384 4.4 2.2 3.9 1.7
9‑12 Bre 678 499 0.46 742 448 0.78 4.1 1.3 0.49 4.3 2.0 1.61
Bot 720 458 799 319 4.0 1.4 3.8 1.1
12‑20 Bre 1351 554 0.12 1250 687 1.16 6.3 2.4 0.27 6.1 2.5 1.75Bot 1364 647 1382 565 6.2 2.5 6.9 2.1 Bre= Breast‑fed,Bot= Bottle‑fed * * : p<0.01
12
group was slightly higher than the Japanese standard throughout the study period for boys and until the 6th month for girls. The mean length of the infants in the bottle group was sig‑
nificantly more than that of the breast group in the lst and 9th months for boys, and in the lst and 6th months for girls. However, in the 12th and 20th months the differences in both sexes were not significant. The mean length of infants in the breast group was slightly less than that of the Japanese standard, but were almost equal to the standard at the 12th and the 20months.
Table 2 shows the increases in weight and length in breast and bottle groups during three・months intervals. The mean increases in weight in each 3‑month period except during 0‑3 months were consistently greater in the bottle group than in the breast group for both sexes. For girls the differences in mean increases between breast and bottle groups were sig‑
nificant during the 6‑9 month period (p <0.01). As for the mean increases in length during three months, no marked difference was observed between the breast and bottle groups in either sex.
Figure 1 shows comparisons between the breast and bottle groups with regard to the re‑
lative frequency distribution of weight in the eight categories in both sexes at birth and at 6, 9, 12, and 20 months. The distribution in the bottle group tended to show a shift towards the right (to the heavier side) indicating that there were more heavier infants in the bottle group than in the breast group. These differences increased slightly with age and were significant in 12 and 20 months in girls (P <0.05). The differences in distribution of length between
the bottle and breast groups were much smaller than those in weight.Figure 2 shows the distribution of changes in weight categories from birth to 3 months, 3 to 6 months, 6 to 12 months, and 12 to 20 months in both sexes. In this figure, the positive
>
3 N u
⊃ 0 山
∝ j
12345 67 8 1 234 5678
CATEGORY
D: Kormogorov‑Smilnov Statistics I: Pく0.05
Figure 1. Comparison of relative frequency distributions of weight between breast and bottle groups.
The abscissa is the categorized number by the 3rd, 10th, 25th, 50th, 75th, 90th and 97th percentiles of weights.
BOYS 旧LS
‑3‑2‑101234 ‑3‑2‑101234
(20 monthsトtでnwlh)
CATEGORY DIFFERENCES
D: Kormogorov‑Smirnov Statistics
Figure2. Comparison of the distributions of changes in weight categories between breast and bot‑
tiegroups.
The abscissa is the number obtained by subtracting the category number of the begin‑
ning month from that of the final month in each period.
A O N 3
⊃
○ 山
∝
﹂
‑6 ‑5 ‑4 ‑3 ‑ ‑1
CATEGORY DIFFERENCES (Weight) ‑ (Length) D: Kormogorov‑SmirnovもStatistics * p<0.05
Figure3. Comparison of the distributions of the difference between categories of weight and length at 12 and 20 months in girls between the breast and bottle groups.
and negative numbers mean change towards the upper and the lower percentile categories, respectively. The changes in categories from birth to 3 months are widely distributed, but af‑
ter that period the distribution is narrower, indicating that changes in weight categories are greater at an earlier age, irrespective of the type of feeding. For changes in weight categories between 3 and 6 months and between 6 and 12 months for both boys and girls, the proportion of infants who shifted towards the smaller categories were relatively higher in the breast group than in the bottle group for both sexes, whereas, the proportion of infants who shifted to the larger categories was higher in the bottle group than in the breast group,
Figure 3 shows the distribution of differences between percentile categories of weight and length at 12 and 20 months in the breast and bottle groups in girls. The number on the abscissa was obtained by subtracting the length category number from the weight category number. The number of infants who were in smaller weight categories, compared with their length category was much higher in the breast than in the bottle group, while, numbers of in‑
fants in the larger weight categories compared with their length category were much greater in the bottle than in the breast group, and the difference between the breast and bottle
groups in 12 months was significant (P <0.05).
Table3. Effects of feeding type on weight and length at 20 months of age by multiple regression analysis (stepwise method).
Girls (n ‑144) Boys (n ‑154) Dep.Var. Step Var. Step Var.
WEIGHT 1 birthweight 0.287 0.082 0.285** 1 birthweight 0.380 0.442**
2 BOTTLE‑FEEDING 0.382 0.146 0.253** 2 gestationperiod 0.468 ‑0.274**
3 mother's weight 0.499 0.171*
4 father'sheight 0.520 0.1485*
LENGTH 1 father'sheight 0.316 0.100 0.290** 1 birthweight 0.338 0.367**
2 birthheight 0.406 0.165 0.222** 2 mother'sweight 0.442 0.277**
3 mother'sweight 0.444 0.197 0.184** 3 gestationperiod 0.477 ‑0.177*
4 BOTTLE‑FEEDING 0.471 0.222 0.157* 4 father'sheight 0.500 0.148*
* * : P <0.01, * : P <0.05 Probability ofF value to enter p ‑0.05, Dummy variable: Bottle‑feed‑
ing ‑1, others =0 ; Excluded variables in all analyses : age of mother, breast‑feeding, height of mother, weight of father, birth order, period of breast‑feeding, month of addition of solid food ; R ‑ Coefficient of multiple regression, β ‑ Standardized coefficient
Table 3 shows the results of the multiple regression analysis of weight and length at 20 months. Only variables that had significant effects at P <0.05 level were shown in the table.
Bottle‑feeding was a variable that had positive effects on weight and length in girls ; the weight and length of girls were significantly greater at the 20th month in the bottle group than in the breast and mixed groups. The R value showed that the feeding type accounted for 6.4% and 2.5% of the variations in weight and length, respectively. Almost the same re‑
suits were obtained from the multiple regression analysis of weight and length in girls at 12 months of age. However, in boys, the feeding type was not a significant factor affecting weight or length at 12 or 20 months of age.
Discussion
The results of this study show that there is a difference in the growth patterns of in‑
fants according to the type of feeding. Breast‑fed infants tend to be shorter and lighter in weight than bottle‑fed infants. These findings accord well with those in several previous re‑
ports, which have indicated that healthy infants who are breast‑fed for comparatively long periods tend to be lighter in weight, to be shorter, and to have smaller fat‑folds than infants
(13)
who are bottle‑fed from birth or have been switched to mixed feeding at an early stage However, the differences in length distribution, accordingly, the differences in mean length between the breast‑ and bottle‑fed infants were much smaller, or negligible, compared with the relatively great differences observed in the weight distribution and the great differ‑
ence of mean weight between the two groups, especially after 6 months of age. Since length is also a reliable indicator for evaluating infant growth, that there was no significant difference
observed in length between the breast‑ and bottle‑fed infants suggests that the development of the breast‑fed infants was not necessarily inferior to that of the bottle‑fed infants, although the mean weight of the breast‑fed infants was less than that of those who were bottle‑fed.
Further, when infants at each designated month of age were divided into eight categories according to the 3rd, 10th, 25th, 50th, 75th, 90th, and 97th percentiles of weight and length, it was found that a realtively large number of the breast‑fed infants shifted to the lighter weight categories, and a relatively large number of bottle‑fed infants shifted to the heavier weight categories during the 3‑ to 6‑month and 6‑ to 12‑month periods ; this was so for both sexes. However, such tendencies were not observed with changes in length categories. Most infants ingest some solid food in addition to milk after 7 months of age at the latest, and the findings that the differences in mean weight between breast‑ and bottle‑ fed infants became greater after 6 months of age and that many breast‑fed infants towards heavier weight cate‑
gories at the 3‑ to 6‑month and 6‑ to 12‑month intervals appear somewhat strange. Stuff and
(7)
Nichols demonstrated that, in infants fed exclusively on human milk, the energy intake per kilogram of body weight did not increase after ad libitum addition of solid food to their diet, although the milk intake decreased. In their view, breast‑fed infants maintain an adequate energy intake after weaning, so it could be assumed that the discrepancy in mean weight be‑
tween breast‑ and bottle‑fed infants which increases after 6 months of age, in particular, is,
at least in part, due to the over feeding of the bottle‑fed infants. We found that the tendency to over feed with bottled milk was greater in girls than in boys. This fact may suggest that girls are more likely than boys to be affected by the method of feeding and to gain fat even in infancy.
It is necessary to construct a standard growth curve for the length and weight of breast‑
fed infants based on a larger number of healthy breastイed infants in various communities.
Longitudinal data are preferable, as has been pointed out by Tanner
(14)
Acknowledgements
We thank Dr. Noriko Kato of the National Institute of Public Health for her assistance in
the use of the spline function computer program.
References
1 ) Whitehead, RG., and Paul, AA., 1984. Growth charts and the assessment of infant feeding practices in the western world and in developing countries. Early Development, 9, 187‑207.
Owen, GM., Garry, PJ., Hooper, EM., 1984. Feeding and growth of infants. Nutritional Research, 4, 727‑731.
3 ) Duncan, B., Schaefe, C, Sibley, B., and Fonseca, NM., 1984. Reduced growth velocity in exclusively
breast‑fed infants. A耶erican Journal of Dieases of Children. 138, 309‑313.4 ) Salmenpera, L., Perheentupa, J., and Siimes, MA., 1985. Exclusively breast‑fed healthy infants grow slower than reference infants. Pediatric Research. 19, 307‑312.
