The authors have declared that no competing interests exist.
The objectives of this longitudinal study were to examine the trajectory of breastfed infants’ growth in China to update growth standards for early childhood, and to compare these updated Chinese growth standards with the growth standards recommended by the World Health Organization (WHO) in 2006.This longitudinal cohort study enrolled 1,840 healthy breastfed infants living in an "optimal" environment favorable to growth and followed up until one year of age from 2007 to 2010. The study subjects were recruited from 60 communities in twelve cities in China. A participating infant’s birth weight was measured within the first hour of the infant’s life, and birth length and head circumference within 24 hours after birth. Repeated weekly and monthly anthropometric measurements were also taken. Multilevel (ML) modelling via MLwiN2.25 was fitted to estimate the growth curves of weight-for-age (WFA), length-for-age (LFA), and head circumference-for-age (HFA) for the study sample as a whole and by child sex, controlling for mode of delivery, the gravidity and parity of the mother, infant’s physical measurements at birth, infant’s daily food intaking frequency per day, infant’s medical conditions, the season when the infant’s physical measurement was taken, parents’ ages, heights, and attained education, and family structure and income per month. During the first four weeks after birth, breastfed infants showed an increase in weight, length, and head circumference of 1110g, 4.9 cm, and 3.2 cm, respectively, among boys, and 980 g, 4.4 cm, and 2.8 cm, respectively, among girls. Throughout infancy, the total growth for these three was 6930 g, 26.4 cm, and 12.5 cm, respectively, among boys, and 6480 g, 25.5 cm, and 11.7 cm, respectively, among girls. As expected, there was a significant sex difference in growth during the first year. In comparison with the WHO growth standards, breastfed children in our study were heavier in weight, longer in length, and bigger in head circumference, with the exception of a few age points during the first two to four months on the upper two percentile curves.Our data suggested the growth curves for breastfed infants in China were significantly different in comparison with those based on the WHO standards. The adoption of the WHO infant growth standards among Chinese infants, as well as the methods used in the development of such growth standards in China, need careful and coordinated consideration.
Attained growth is the most widely used means to assess childhood growth patterns [
In recent years, growth standards developed from healthy breastfed infants have been used as a normative standard to assess the nutritional and health status of children, which has important public health implications for obesity prevention [
Nevertheless, questions emerged regarding the applicability of the WHO standards in various countries and regions [
Since the 1970s, many studies on children’s physical development have been conducted in China. For instance, national growth surveys of children under seven years were conducted in nine cities every decade [
Therefore, the objectives of this longitudinal study are: a) to describe the trajectory of breastfed infant growth for infants in China to develop a more updated growth standard for early childhood; b) to delineate the determinants of the growth trajectory; c) to understand the growth characteristics of breastfed infants in China compared to the WHO standards. The methodology of this study was largely based on the MGRS protocol [
This study was a population-based longitudinal study from Jan. 2007 to Jan. 2010. Field implementation was undertaken by the Maternal and Child Health Care Surveillance System (MCHCSS) in China, which provides postnatal care including immunization, physical examinations, and growth monitoring at no cost to infants and children from birth to seven years. The inclusion criteria for study sites were made to match the WHO criteria for living in an "optimal" environment favorable for growth [
The selection of study sites was based on a three-stage sampling at the provincial, municipal, and community levels, separately. At the provincial level, in addition to the inclusion ctieria described above, the selection decision was made on the basis of geographic distribution (3–4 provinces were included in each of the three major geographic regions in China: the North, South, and Central regions), the integrity and technical capacity of MCHCSS, and participation interest. As a result, 11 provinces were selected among those that meet the inclusion criteria.
At the municipal level, one city per study province was chosen, often being the provincial capital city. Jingmen of Hubei was additionally selected, as it expressed high interest in this study and met the screening standards. Thus, 12 cities were enrolled. At the communities level, different numbers of representative communities from each city were selected to ensure sufficient eligible samples. Thus, a total of 60 communities from 12 cities were finally included in this study.
The subjects included in this study were healthy breastfed infants living in an "optimal"environment favorable for growth. The inclusion criteria for families consisted of no health-related, environmental, or economic constraints on infant growth; non-consanguineous marriage for parents; both or one of the parents having urban registration; the mother-infant pair living together, routine well-baby checkups at least up to age one; and parents willing to participate in one-year follow-up and signing of the consent form. Eligible mothers were of singleton pregnancy, a maternal age between 20 and 35 years old, had a height ≥ 1.5 m, without pregnancy complications (e.g. anemia, pregnancy induced hypertension, and diabetes), nonsmokers, and willing to deliver at designated hospitals. Only infants born to the eligible mothers with gestational age ≥ 37 completed weeks and < 42 weeks, birth weight ≥ 2500 g and < 4000 g, free of serious or life-threatening conditions at birth (e.g. congenital disease, asphyxia, birth trauma), without significant morbidity during the first year after birth (e.g. hypoxic-ischemic encephalopathy, heart disease, blood diseases, chronic nephritis, tuberculosis, chronic bronchitis, chronic diarrhea), and mothers’ compliance with feeding recommendations for this study were included.
The feeding recommendations of this study were defined as follows: 1) exclusive or predominant breastfeeding for a minimum of four months and optimally for six months of age, as suggested by national policies; 2) introduction of complementary foods between four and six months of age; and 3) continuing partial breastfeeding up to at least 12 months of age. The definitions of exclusive or predominant breastfeeding and partial breastfeeding refer to the Breastfeeding Counseling Training Course released by the WHO, as well as lactation counseling and infant feeding guidelines provided to the mothers [
This study was IRB approved by the Ethical Review Committee of the National Center for Women and Children's Health Chinese Center for Disease Control and Prevention. The approval number was FY2007-002. We also obtained written informed consent from parents on behalf of the children enrolled in our study.
Infants’ anthropometric measurements included three indices: weight, length, and head circumference, and were taken at birth, weekly during the first month after delivery, and monthly from two to twelve months of age. Birth weight was measured within the first hour of the infant’s life. Birth length and head circumference were measured within 24 hours after birth. Weekly and monthly measurements were taken within 23 hours of the designated infant’s age. Replicate measures were obtained for each measurement and the average values were used. The differences in replicate measures were limited to 100 g for weight and 5 mm for length and head circumference. All anthropometrists underwent the systemic standardized anthropometric training before and during the study and followed the unified anthropometry manuals. All study sites used the same high-precision measuring equipment. Regular calibration for all tools was performed daily at the community level, quarterly by urban anthropometric experts appointed for the study, and bi-annually by the National Center for Women and Children Health (NCWCH), that was in charge of this study.
Quality control procedures were critical to data quality and included the following: a) construction of a longitudinal study network from national to community level, consisting of data coordination, collection, and management; quality control; and advisory for groups; b) prior to implementation, the staff from each work group underwent thorough training to standardize the protocol for anthropometric measurements, feeding methods recommendations, and questionnaire survey administration; c) pilot testing of study protocol; d) regular visits to study sites (monthly at the district level, quarterly at the city level, and semi-annually at the national level) for the calibration of measurement tools, technology capacity assessment for filed researchers who conducted the anthropometric measurements, and home and telephone interviews; e) data quality assurance through calibration of equipment, standardization of measurements and surveys, and standardizing and auditing data entry; f) routine coordination of meetings, retraining, and staff exchanges at different levels.
To accommodate the multistage-sampling and the repeated measurement data collected in this study, we conducted multilevel (ML) growth curve modelling [
From July 1, 2007 to July 30, 2008, 1840 (67.4%: 905 boys and 935 girls) eligible mother-infant pairs were enrolled in the study, among which 1513 (82.2%) subjects completed the one-year follow-up, and 327 (17.7%) subjects had at least one missing assessment due to scheduling conflicts (54.7%), moving out of the study sites (33.3%), child illnesses (6.1%), mother illnesses (0.9%), and unknown or other reasons (4.9%).
The demographic characteristics of 1840 subjects were presented in
Demography | Total | Conpliant | Non-compliant | Comparison |
---|---|---|---|---|
Mother’s age, mean±SD, t(p) | 28.0±3.8 | 28.0±3.7 | 28.0±4.0 | 0.24(0.8096) |
Mother’s height, mean±SD, t(p) | 160.5±4.6 | 160.6±4.5 | 160.2±4.8 | 1.55(0. 1217) |
Father’s age, mean±SD, t(p) | 30.8±4.4 | 30.8±4.4 | 30.8±4.7 | 0.11(0.9092) |
Father’s height, mean±SD, t(p) | 172.5±5 | 172.6±5.1 | 172.1±4.8 | 1.47(0.1420) |
Delivery(%),Chi-Square(p) | 2.09(0.3521) | |||
Vaginal delivery | 44.4 | 45.1 | 41.1 | |
Caesarean section | 54.9 | 54.2 | 58.0 | |
Forceps delivery | 0.7 | 0.6 | 0.9 | |
Mother’s attained education(%), Chi-Square(p) | 73.76 (<0.0001) | |||
Primary school and under | 10.8 | 8.4 | 21.1 | |
Junior high school | 27.1 | 26.8 | 28.5 | |
High school(technical secondary school) | 44.3 | 44.5 | 43.7 | |
University(college) | 16.5 | 18.9 | 6.5 | |
Graduate and above | 1.3 | 1.5 | 0.3 | |
Father’s attained education(%), Chi-Square(p) | 66.41(<0.0001) | |||
Primary school and under | 7.7 | 6.0 | 14.7 | |
Junior high school | 24.2 | 23.0 | 29.0 | |
High school(technical secondary school) | 47.1 | 47.0 | 47.6 | |
University(college) | 19.8 | 22.5 | 8.5 | |
Graduate and above | 1.2 | 1.5 | 0.3 | |
Family structure(%),Chi-Square(p) | 9.27(0.0259) | |||
Nuclear family | 53.8 | 52.8 | 57.8 | |
Consanguineous family | 42.6 | 43.9 | 36.5 | |
Joint family | 3.4 | 2.9 | 5.4 | |
Single parent | 0.3 | 0.3 | 0.3 | |
Household monthly income(%),Chi-Square(p) | 8.57 (0.1276) | |||
<1000 RMB | 2.4 | 2.2 | 3.4 | |
1000–2000 RMB | 14.2 | 14.0 | 15.1 | |
2001–3000 RMB | 22.8 | 22.6 | 23.6 | |
3001–5000 RMB | 35.3 | 36.7 | 39.3 | |
5001–8000 RMB | 17.8 | 17.3 | 20.2 | |
>8000 RMB | 7.5 | 7.2 | 8.5 |
a T test and Chi-Square were used to conduct the comparison on numeric variables and Categorical variables respectively between compliant and non-compliant group.
From top to bottom is 97th, 85th, 50th, 15th, and 3rd.
Parameters | Birth Weight | Birth Length | Birth Head Circumference | |||
---|---|---|---|---|---|---|
Estimate(s.e.) |
Estimate(s.e.) |
Estimate(s.e.) |
||||
Intercept | -3.421(0.354) | <0.001 | -13.886(1.447) | <0.001 | -6.351(1.115) | <0.001 |
Sex = Boy | 0.007(0.015) | <0.001 | 0.401(0.061) | <0.001 | 0.334(0.047) | <0.001 |
Sex = Girl | Reference | |||||
Mode of delivery = Cesarean section | 0.306(0.05) | <0.001 | ||||
Mode of delivery = Vaginal births | Reference | |||||
Motherage | 0.006(0.002) | 0.009 | ||||
Motherheight | 0.012(0.002) | <0.001 | 0.049(0.007) | <0.001 | 0.021(0.006) | 0.000 |
Mother education = High school | -0.291(0.082) | 0.000 | ||||
Mother education = Bachelor and over | 0.02(0.131) | 0.882 | ||||
Mother education = Junior high school and under | Reference | |||||
Fatherheight | 0.008(0.002) | <0.001 | 0.034(0.007) | <0.001 | 0.016(0.005) | 0.002 |
Father education = High school | 0.214(0.083) | 0.010 | -0.048(0.055) | 0.387 | ||
Father education = Bachelor and over | 0.002(0.126) | 1.000 | -0.157(0.078) | 0.043 | ||
Mother education = Junior high school and under | Reference | |||||
Level 2(community) |
0.003(0.001) | <0.001 | 0.165(0.043) | <0.001 | 0.141(0.034) | <0.001 |
Level 1(subject) | 0.1(0.003) | 0.014 | 1.625(0.055) | 0.000 | 0.94(0.032) | <0.001 |
-2 |
995.897 | 5996.419 | 4928.687 |
a Standard errors in brackets.
b, As results shown, all the random coefficients were statistically significant (PWald test <0.05), indicating that infants’ physical status at birth presented significantly different from different communities.
c -2*loglikelihood (Iterative Generalised Least Squares (IGLS) Deviance).
Parameters | Weight-for-age | Length-for-ge | Head circumference-for-age | |||
---|---|---|---|---|---|---|
Estimate(s.e.) |
Estimate(s.e.) |
Estimate(s.e.) |
||||
Intercept | -5.228(0.294) | <0.001 | -40.019 (1.402) | <0.001 | -22.255(0.659) | <0.001 |
Age | -0.004(0.001) | <0.001 | -0.063(0.007) | <0.001 | -0.007(0.001) | <0.001 |
Age2 | 0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 |
Age3 | 0.000(0.000) | <0.001 | 0.000(0.000) | 0.001 | 0.000(0.000) | <0.001 |
Age4 | 0.000(0.000) | <0.001 | 0.000(0.000) | 0.001 | ||
Sex = Boy | -0.072(0.014) | <0.001 | 0.099(0.032) | 0.002 | ||
Sex = Girl | Reference | |||||
Sex = Boy×Age | 0.009(0.001) | <0.001 | 0.014(0.001) | <0.001 | 0.009(0.001) | <0.001 |
Sex = Boy×Age2 | 0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 |
Sex = Boy×Age3 | 0.000(0.000) | <0.001 | 0.000(0.000) | 0.000 | 0.000(0.000) | 0.002 |
Sex = Boy×Age4 | 0.000(0.000) | <0.001 | 0.000(0.000) | 0.005 | 0.000(0.000) | 0.022 |
Disease = With disease | -0.059(0.005) | <0.001 | -0.046(0.017) | 0.007 | ||
Disease = Without disease | Reference | |||||
Season = Summer | 0.009(0.010) | 0.346 | 0.132(0.033) | <0.001 | ||
Season = Autumn | 0.023(0.011) | 0.041 | 0.303(0.039) | <0.001 | ||
Season = Winter | 0.014(0.01) | 0.166 | 0.168(0.035) | <0.001 | ||
Season = Spring | Reference | |||||
Season = Summer×Age | 0.000(0.000) | 0 | 0.000(0.000) | 0.013 | ||
Season = Autumn×Age | 0.000(0.000) | <0.001 | -0.001(0.000) | 0.000 | ||
Season = Winter×Age | 0.000(0.000) | 0.017 | 0.000(0.000) | 0.021 | ||
Birthweight | 0.792(0.021) | <0.001 | 1.04(0.091) | <0.001 | 0.395(0.056) | <0.001 |
Birthlength | 0.028(0.005) | <0.001 | 0.555(0.021) | <0.001 | 0.033(0.013) | 0.010 |
Birthhead | 0.025(0.006) | <0.001 | 0.075(0.025) | 0.003 | 0.568(0.015) | <0.001 |
Gravida = Non-first pregnancy | 0.031(0.014) | 0.031 | ||||
Gravida = First pregnancy | Reference | |||||
Gravida = Non-first pregnancy×age | -0.001(0.000) | 0.000 | ||||
Parity = Non-first birth | 0.056(0.025) | 0.028 | ||||
Parity = First birth | Reference | |||||
Mode of delivery = Cesarean section | -0.026(0.011) | 0.014 | ||||
Mode of delivery = Vaginal births | Reference | |||||
Motherage | -0.003(0.002) | 0.063 | ||||
Motherheight | 0.019(0.005) | 0.000 | ||||
Motherheight×Age | 0.000(0.000) | <0.001 | ||||
Mother education = High school | -0.013(0.012) | 0.249 | 0.055(0.048) | 0.256 | ||
Mother education = Bachelor and over | 0.003(0.017) | 0.862 | 0.159(0.073) | 0.030 | ||
Mother education = Junior high school and under | Reference | |||||
Mother education = High school×Age | 0.001(0.000) | 0.001 | ||||
Mother education = Bachelor and over×Age | 0.001(0.000) | 0.001 | ||||
Fatherheight | 0.003(0.001) | 0.005 | 0.018(0.005) | 0.000 | ||
Fatherheight×Age | 0.000(0.000) | <0.001 | ||||
Formula | 0.005(0.002) | 0.033 | 0.025(0.008) | 0.001 | ||
Cereal | -0.017(0.006) | 0.003 | ||||
Meat | -0.049(0.016) | 0.002 | ||||
Bean | 0.026(0.013) | 0.045 | ||||
Vegetable | 0.011(0.004) | 0.017 | 0.030(0.014) | 0.030 | ||
Fruit | 0.014(0.005) | 0.004 | ||||
Level 3(community) |
||||||
σ2 |
0.003(0.001) | 0.001 | 0.189(0.042) | <0.001 | 0.055(0.013) | <0.001 |
Level 2(infant) |
||||||
σ2 |
0.037(0.002) | <0.001 | 0.664(0.029) | <0.001 | 0.28(0.012) | <0.001 |
σ |
-0.001(0.000) | <0.001 | -0.003(0.000) | <0.001 | -0.001(0.000) | <0.001 |
σ2 |
0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 |
σ |
0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 |
σ |
0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 |
σ2 |
0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 | 0.000(0.000) | <0.001 |
Level 1(visit) | ||||||
σ2 |
0.048(0.001) | <0.001 | 0.532(0.006) | <0.001 | 0.162(0.002) | <0.001 |
-2 |
8751.320 | 60100.724 | 344442.472 |
a H0 for fixed effects degree; H1 for random effects degree
b Standard errors in brackets
c σ2
d σ2
e -2*loglikelihood (Iterative Generalised Least Squares (IGLS) Deviance).
It is noteworthy that on 97th percentile curve of WFA, the difference between the raw data and the predicted value became larger after 10 months old, which may be due to the degree of dispersion in our data. It appears that the older age a child was, the greater the degree of dispersion was observed for WFA, compared to LFA or HFA.
We further stratified our analysis by child sex. As expected, there was a significant sex difference in growth during the first year (P child sex value <0.0001, Tables
Boys’ predicted percentile curves are represented with solid lines and girls’ curves with dotted lines. From top to bottom is 97th, 85th, 50th, 15th, and 3rd percentile.
The growth medians and the corresponding standard deviations were also detailed in
Age | Boys | Girls | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Weight-for-age (kg) | Length-for-age (cm) | Head circumference-for-age (cm) | Weight-for-age (kg) | Length-for-age (cm) | Head circumference-for-age (cm) | |||||||
Median | SD | Median | SD | Median | SD | Median | SD | Median | SD | Median | SD | |
Birth | 3.36 | 0.32 | 50.1 | 1.3 | 34.1 | 1.0 | 3.26 | 0.32 | 49.9 | 1.3 | 33.9 | 1.0 |
Week 1 | 3.39 | 0.34 | 51.1 | 1.4 | 34.8 | 0.9 | 3.30 | 0.34 | 50.8 | 1.3 | 34.4 | 0.9 |
Week 2 | 3.73 | 0.34 | 52.4 | 1.4 | 35.7 | 0.9 | 3.58 | 0.34 | 51.9 | 1.3 | 35.2 | 0.9 |
Week 3 | 4.11 | 0.34 | 53.6 | 1.4 | 36.5 | 0.9 | 3.90 | 0.35 | 53.1 | 1.4 | 35.9 | 0.9 |
Week 4 | 4.47 | 0.36 | 55.0 | 1.4 | 37.3 | 0.9 | 4.24 | 0.35 | 54.3 | 1.3 | 36.7 | 0.9 |
month 2 | 5.86 | 0.44 | 59.1 | 1.4 | 39.2 | 0.9 | 5.49 | 0.45 | 58.2 | 1.4 | 38.5 | 0.9 |
Month 3 | 6.79 | 0.54 | 62.4 | 1.5 | 40.6 | 0.9 | 6.35 | 0.56 | 61.2 | 1.5 | 39.8 | 0.9 |
Month 4 | 7.51 | 0.64 | 64.7 | 1.6 | 41.9 | 0.9 | 7.04 | 0.66 | 63.5 | 1.6 | 41.0 | 0.9 |
Month 5 | 8.05 | 0.73 | 66.8 | 1.7 | 42.8 | 1.0 | 7.53 | 0.75 | 65.5 | 1.7 | 41.9 | 1.0 |
Month 6 | 8.51 | 0.78 | 68.7 | 1.8 | 43.7 | 1.0 | 8.04 | 0.80 | 67.4 | 1.8 | 42.8 | 1.0 |
Month 7 | 8.86 | 0.82 | 70.2 | 1.8 | 44.4 | 1.1 | 8.36 | 0.84 | 68.9 | 1.8 | 43.4 | 1.1 |
Month 8 | 9.21 | 0.86 | 71.8 | 1.9 | 44.9 | 1.1 | 8.68 | 0.88 | 70.4 | 1.9 | 43.9 | 1.1 |
Month 9 | 9.48 | 0.90 | 73.0 | 2.0 | 45.4 | 1.1 | 8.95 | 0.89 | 71.7 | 1.9 | 44.5 | 1.1 |
Month 10 | 9.76 | 0.90 | 74.2 | 2.0 | 45.7 | 1.0 | 9.25 | 0.92 | 72.9 | 2.0 | 44.8 | 1.0 |
Month 11 | 9.98 | 0.91 | 75.3 | 2.1 | 46.1 | 1.0 | 9.48 | 0.94 | 74.1 | 2.0 | 45.2 | 1.1 |
Month 12 | 10.29 | 0.91 | 76.5 | 2.1 | 46.6 | 1.0 | 9.74 | 0.96 | 75.4 | 2.0 | 45.6 | 1.0 |
In comparison with the WHO growth standards [
Boys’ mean z score represented with solid lines, and girls’ with dotted lines. Most of the z values were statistically significant, except the six age points: birth for WFA-Boys; W2 for WFA-Gilds; W1 and W2 for LFA-Boys; birth and W2 for HFA-Girls.
Compared to the WHO standards [
We further compared the growth percentile curves of WFA, LFA, and HFA by child sex from the present study to the WHO standard percentile curves. As
Findings fom this study were represented with lines and WHO with triangle signs. From top to bottom represents the 97th, 85th, 50th, 15th, and 3rd percentiles.
The boys and girls included in our study fell below the WHO standards by 60–400 g and 270–340 g, respectively, during the first three months after birth, but were above the WHO standards by 210–470 g and 300–510 g, respectively, for the remaining study period until 12 months of age, when the corresponding values of the WHO standard approximately equaled the predicted 91st-93rd values of the present study. Notable differences were also found in the 15th and 3rd percentile curves. The values of the 15th curve of boys’ WFA or LFA in the WHO Standards were close to the corresponding values of our 1st-3rd or 3rd-8th percentile curves, respectively, and those of the 3rd curve were below the lowest limit of our populations. Similar results were also evident for the girls group.
Consequently, during the first year of life, estimates of obesity (with the 97th percentile of weight-for-age as the cut-off point) for Chinese infants were higher when based on the standard draw from the WHO MGRS, while underweight (with the 3rd percentile of weight-for-age as the cut-off point), and stunting (with the 3rd percentile of length-for-age as the cut-off point) were lower.
Compared to the infant growth reference from the 2005 nine-city study (3), the growth levels reached by breastfed infants on the 97th percentile curve in our study were relatively lower both for weight and length. The differences between the two studies across the first year were 280–560 g and 1.1–1.4 cm for boys and 10–370 g and 0.7–1.5 cm for girls, respectively. However, conflicting results occurred on the 50th curve, as well as the lower two percentile curves. Especially on the 3rd percentile curve, the boys’ weights and lengths in our study were 120–630 g and 1.2–1.9 cm above the current national reference, which also presented in the girls group.
The present study was the first longitudinal study of breastfed infants based on a large sample of Chinese children. Compared to Chinese growth standards developed 25 years ago by means of a longitudinal study design [
The considerable divergence in infant growth between our study and the 2005 nine-cities study, as noted above, likely resulted from the differences in study design and the characteristics of study samples, specifically from the differences in the types of feeding methods for the enrolled subjects. In the nine- cities study, 36.3% of the study sample reported partially breast-feeding during the first four months and 15.1% exclusively formula-feeding. Only 48.6% of infants were exclusively or predominantly breastfeeding [
An updated infant growth standard based on data from longitudinal studies from a study sample meeting the recommended feeding practices is critical to provide an appropriate reference for the optimal growth and development of healthy Chinese children during their first year of life. In comparison with the growth curves of the WHO standards [
Noteworthy, the weight and length values of Chinese infants from this study were shown to be slightly lower at birth (average differences of 220 g and 0.69 cm among boys and 190 g and 0.19 cm among girls) as compared to the reference issued in Sweden [
In view of these findings, the adoption of the WHO infant growth standards in China would result in an increased number of Chinese infants classified as overweight or obese but a decreased number of infants classified as underweight or stunted. With a vast territory, significant regional differences in child development exist in China. In urban areas, where obesity has become the main public health problem, the WHO standards might be helpful to avoid excess weight gain but probably will lead to inappropriate assessment concerning weight-for-age, resulting in needless parental worrying. By contrast, in rural areas, especially in Western China, malnutrition is still the most common health problem adversely affecting child growth. Quite a few malnourished infants would be classified as having normal development by the infant growth standard based on the WHO MGRS study and subsequently miss out on early interventions.
Similar results were reported from Juliusson et al. on Norwegian and Belgian children that the number of Belgian and Norwegian children below -2 SD lines of the WHO standards was lower and above +2 SD higher than expected [
The strengths of the present study include its prospective design with repeated measures on breastfeeding infant growth. Most previous research on infant growth was limited by cross-sectional study design and without the clear definition of infant feeding methods [
In conclusion, our study was a large, longitudinal-based study of a sample of healthy breastfed Chinese infants. This study showed that the growth curves for breastfed infants in China were significantly different in comparison with those based on the WHO MGRS study, as well as those from the current national growth standards based on the Chinese nine-cities study. The adoption of the WHO infant growth standards among Chinese infants, as well as the methods used in the development of such growth standards in China, need careful and coordinated consideration.
This study was a multi-center study. We gratefully thank all the members of the Chinese Breastfeeding Infants’ Growth Reference Study Group and all the families that participated in the study. Also thanks to the Ministry of Science and Technology of the People's Republic of China and the Ministry of Health of the People’s Republic of China for its support.