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Pediatrics International (2015) 57, 126–130
doi: 10.1111/ped.12421
Original Article
Predictors of early introduction of complementary feeding: Longitudinal study Li Tang, Andy H Lee and Colin W Binns School of Public Health, Curtin University, Perth, Western Australia, Australia Abstract
Background: Early introduction of complementary foods prior to 6 months of age may shorten breast-feeding duration and expose the infant to increased risk of morbidity and mortality. The aims of this study were to document the ages of complementary food introduction and to identify the determinants associated with early introduction of complementary feeding in Sichuan Province. Methods: A prospective study on infant feeding practices was conducted during 2010–2011 in Jiangyou, China. A total of 695 mothers were recruited and interviewed at discharge. The follow-up interviews were carried out by telephone at 1, 3 and 6 months postpartum. Cox regression analysis was performed to determine factors related to early introduction of complementary feeding. Results: The median age at start of complementary feeding was 4.5 months (95% confidence interval [CI]: 4.4–4.6 months). Mothers who perceived that most of their friends breast-fed (adjusted hazard ratio [HR], 0.70; 95%CI: 0.58–0.84) and those who returned to work when the infants were at least 6 months old were less likely to initiate complementary feeding early (adjusted HR, 0.73; 95%CI: 0.58–0.91), while infants who had been introduced to infant formula regularly before 6 months of age were at a higher risk of receiving complementary foods prematurely (adjusted HR, 1.81; 95%CI: 1.42–2.31). Conclusions: Introducing complementary feeding before 6 months postpartum was widely practiced in Jiangyou. The appropriate age at which to introduce complementary foods and its benefits need to be emphasized in the future breast-feeding education strategies in Sichuan.
Key words breast-feeding, China, cohort study, complementary food.
Appropriate feeding practices during infancy are important in achieving optimal health, growth and development.1,2 In 2001, following a commissioned systematic review and expert consultation on the optimal duration of exclusive breast-feeding, the World Health Organization (WHO) revised its guideline to recommend exclusive breast-feeding for the first 6 months of life.3,4 Complementary foods, defined as foods other than breast milk or infant formula introduced to an infant to provide nutrients, are recommended to be added to the infant’s diet beginning at 6 months of age while continuing to breast-feed.5 The premature introduction of complementary feeding prior to 6 months of age may cause decreased nursing frequency and less sucking time at the breast, resulting in reduced milk production and consequently early breast-feeding cessation.6,7 In addition, early introduction of complementary feeding increases the risk of infant exposure to microbial contaminated foods and fluids, especially in developing countries.8 As a result of
Correspondence: Li Tang, PhD, School of Public Health, Curtin University, GPO Box U 1987, Perth, WA 6845, Australia. Email: li.tang @curtin.edu.au Received 2 February 2014; revised 8 May 2014; accepted 27 May 2014.
© 2014 Japan Pediatric Society
decreased breast milk intake and/or infection by contaminated foods, infants may initially experience malnutrition and poor growth.9 In the longer term, excessive use of complementary foods may lay the foundations for childhood obesity.10 Moreover, a recent study found that infants who were introduced to complementary foods before 6 months of age had a significantly higher occurrence of picky eating behavior during preschool than infants who were exclusively breast-fed for 6 months.11 In spite of these disadvantages, introducing complementary foods before the age of 6 months is almost universal practice in China.12,13 For instance, 39% and 78% of infants in Xinjiang Uygur Autonomous Region had received cow’s milk and solid foods, respectively, by 6 months of age.14 Similarly, a prospective cohort study from Zhejiang Province of eastern China found that 95% of mothers had introduced complementary foods by 6 months postpartum.6 Nevertheless, no cohort studies in southwestern China have reported the age when infants are introduced to complementary foods. Few studies have identified the factors associated with early introduction of complementary feeding across the country. Therefore, we conducted a longitudinal study to investigate the age of complementary food introduction in Sichuan, the most populous Province in south-western China, and to explore factors associated with early introduction of complementary feeding.
Introduction of complementary feeding
127
Methods
Results
A prospective cohort study on infant feeding practices was undertaken during 2010–2011 in Jiangyou, Sichuan Province. Jiangyou is a county-level city with a population of 880 000 located 160 km north of the provincial capital city, Chengdu. Between March and November 2010, a total of 723 mothers who were aged ≥18 years and who delivered single babies at four hospitals and three township health centers in Jiangyou were invited to participate. Women were excluded if they were unable to answer the questions due to limited understanding, illness or deemed unsuitable as advised by health professionals, including doctors, nurses and midwives, at the health facilities. At discharge, a total of 695 eligible women consented to participate (response rate, 96%) and were interviewed face to face by the first author or a trained health facility staff. Follow-up interviews were then conducted at 1, 3 and 6 months postpartum by telephone. The structured baseline and follow-up questionnaires solicited detailed information on sociodemographic and health characteristics, maternal infant feeding intention, maternal satisfaction with infant weight change, infant feeding practices and other data concerning the infant. The questionnaires were taken from those used in our previous studies in Xinjiang and Zhejiang, China, the validity and reliability of which had been verified for Chinese mothers.14,15 By 6 months postpartum, 96 out of 695 mothers (13.8%) were lost to follow up or dropped out of the study: 55 (7.9%) could no longer be reached by telephone, 39 (5.6%) decided not to continue participating, and two (0.3%) were excluded because their infants were severely ill. This project protocol was approved by the Chinese local health authorities and the Human Research Ethics Committee of Curtin University (approval number HR169/2009), and conformed to the provisions of the Declaration of Helsinki. An information letter explaining the project was given and read to each mother before obtaining her written consent. All participants were assured of anonymity and that they could withdraw freely from the study at any time without prejudice.
The 695 participants were aged between 18 and 44 years (median, 24 years). Almost all (99.8%) were married, approximately half received more than 9 years of schooling, and 68.8% of them were employed. Approximately 80% of mothers were delivering their first baby, and 98.4% had a gestation >37 weeks. The infant gender ratio was approximately 1:1, with 94% of birthweight within the range 2.5–4 kg. There were no differences in maternal age, education level, employment status, parity, family monthly income, delivery method, infant gender or infant birthweight between women who completed their participation within 6 months postpartum and those who were lost to follow up (n = 96). In the study, the median age to start complementary feeding was 4.5 months (95% confidence interval [CI]: 4.4–4.6 months). Figure 1 shows the age-specific introduction rates for complementary feeding. Approximately 27% of infants had received complementary foods by the age of 4 months and the rate increased to 90.7% by 6 months. Fruit juice and vegetable juice were the earliest foods introduced to infants in Jiangyou, followed by egg yolk. At 3 months, 14.5% and 1.7% of infants had been given juice and egg yolk, respectively. Three-quarters of the mothers had introduced solid foods to their infants before 6 months postpartum. Table 1 lists the variables that might be expected to have an influence on early introduction of complementary feeding. Univariate Cox regression analysis identified five factors associated with introducing complementary foods prior to 6 months postpartum: maternal education; parity; whether most friends breast-fed their infants; whether infants received formula regularly within the 6 months of life; and the age of the infant when the mother returned to work. Backward stepwise Cox regression analysis (Table 2) confirmed that maternal perception of friends’ breast-feeding behaviors remained as a significant determinant. Mothers who perceived that most friends breast-fed their infants were less likely to initiate complementary feeding before 6 months postpartum (adjusted hazard ratio [HR], 0.70; 95%CI: 0.58–0.84). Returning to employment when the infant was at least 6 months of age was another factor preventing mothers from introducing complementary foods early (adjusted HR, 0.73; 95%CI: 0.58– 0.91). Infants who were fed with infant formula regularly within 6 months, however, were at an elevated risk of receiving complementary foods before 6 months of age (adjusted HR, 1.81; 95%CI: 1.42–2.31).
Statistical analysis
Kaplan–Meier tests were first applied to estimate the median age when complementary foods were introduced. Backward stepwise Cox regression analysis was then conducted to ascertain the determinants of starting complementary feeding before 6 months postpartum. Mothers who completed the 6 month follow-up interview and who did not introduce complementary feeding and those who had not introduced complementary feeding before loss to follow up were the censored observations. The former contributed 6 months of follow up to the Cox regression model and the latter contributed only follow-up time for which they were known to have not introduced complementary feeds. Independent variables considered were chosen from the pertinent literature; they were plausible factors associated with premature complementary feeding and applicable to Chinese mothers residing in Sichuan. Table 1 lists the independent variables used in the Cox regression model. All statistical analysis was performed with IBM SPSS Statistics version 20 (IBM, Armonk, NY, USA).
Discussion Complementary feeding practices documented in the study indicate poor adherence to the WHO recommendations in Jiangyou. Half of the infants had already begun to receive complementary foods by 4.5 months of age. Only one infant remained exclusively breast-fed at age 6 months, and >90% of the infants had received complementary foods. The finding is similar to our previous cohort study in Zhejiang Province, where 95% of infants had been introduced to complementary feeding before 6 © 2014 Japan Pediatric Society
128
L Tang et al.
Table 1 Univariate factors in early introduction of CF (before 6 months of age) Variables Maternal age (years) 3000 Living independently No Yes Parity Primiparous Multiparous Gender of infant Male Female Method of delivery Vaginal delivery Caesarean section Attending antenatal class No Yes Most friends breast-fed their infants No/do not know Yes Intended age of CF introduction Within 6 months After 6 months Do not know Introduction of infant formula within 6 months No Yes Satisfaction with infant weight change Not satisfied/do not know Satisfied Age of infant when mother returned to work
Pediatrics International (2015) 57, 126–130
doi: 10.1111/ped.12421
Original Article
Predictors of early introduction of complementary feeding: Longitudinal study Li Tang, Andy H Lee and Colin W Binns School of Public Health, Curtin University, Perth, Western Australia, Australia Abstract
Background: Early introduction of complementary foods prior to 6 months of age may shorten breast-feeding duration and expose the infant to increased risk of morbidity and mortality. The aims of this study were to document the ages of complementary food introduction and to identify the determinants associated with early introduction of complementary feeding in Sichuan Province. Methods: A prospective study on infant feeding practices was conducted during 2010–2011 in Jiangyou, China. A total of 695 mothers were recruited and interviewed at discharge. The follow-up interviews were carried out by telephone at 1, 3 and 6 months postpartum. Cox regression analysis was performed to determine factors related to early introduction of complementary feeding. Results: The median age at start of complementary feeding was 4.5 months (95% confidence interval [CI]: 4.4–4.6 months). Mothers who perceived that most of their friends breast-fed (adjusted hazard ratio [HR], 0.70; 95%CI: 0.58–0.84) and those who returned to work when the infants were at least 6 months old were less likely to initiate complementary feeding early (adjusted HR, 0.73; 95%CI: 0.58–0.91), while infants who had been introduced to infant formula regularly before 6 months of age were at a higher risk of receiving complementary foods prematurely (adjusted HR, 1.81; 95%CI: 1.42–2.31). Conclusions: Introducing complementary feeding before 6 months postpartum was widely practiced in Jiangyou. The appropriate age at which to introduce complementary foods and its benefits need to be emphasized in the future breast-feeding education strategies in Sichuan.
Key words breast-feeding, China, cohort study, complementary food.
Appropriate feeding practices during infancy are important in achieving optimal health, growth and development.1,2 In 2001, following a commissioned systematic review and expert consultation on the optimal duration of exclusive breast-feeding, the World Health Organization (WHO) revised its guideline to recommend exclusive breast-feeding for the first 6 months of life.3,4 Complementary foods, defined as foods other than breast milk or infant formula introduced to an infant to provide nutrients, are recommended to be added to the infant’s diet beginning at 6 months of age while continuing to breast-feed.5 The premature introduction of complementary feeding prior to 6 months of age may cause decreased nursing frequency and less sucking time at the breast, resulting in reduced milk production and consequently early breast-feeding cessation.6,7 In addition, early introduction of complementary feeding increases the risk of infant exposure to microbial contaminated foods and fluids, especially in developing countries.8 As a result of
Correspondence: Li Tang, PhD, School of Public Health, Curtin University, GPO Box U 1987, Perth, WA 6845, Australia. Email: li.tang @curtin.edu.au Received 2 February 2014; revised 8 May 2014; accepted 27 May 2014.
© 2014 Japan Pediatric Society
decreased breast milk intake and/or infection by contaminated foods, infants may initially experience malnutrition and poor growth.9 In the longer term, excessive use of complementary foods may lay the foundations for childhood obesity.10 Moreover, a recent study found that infants who were introduced to complementary foods before 6 months of age had a significantly higher occurrence of picky eating behavior during preschool than infants who were exclusively breast-fed for 6 months.11 In spite of these disadvantages, introducing complementary foods before the age of 6 months is almost universal practice in China.12,13 For instance, 39% and 78% of infants in Xinjiang Uygur Autonomous Region had received cow’s milk and solid foods, respectively, by 6 months of age.14 Similarly, a prospective cohort study from Zhejiang Province of eastern China found that 95% of mothers had introduced complementary foods by 6 months postpartum.6 Nevertheless, no cohort studies in southwestern China have reported the age when infants are introduced to complementary foods. Few studies have identified the factors associated with early introduction of complementary feeding across the country. Therefore, we conducted a longitudinal study to investigate the age of complementary food introduction in Sichuan, the most populous Province in south-western China, and to explore factors associated with early introduction of complementary feeding.
Introduction of complementary feeding
127
Methods
Results
A prospective cohort study on infant feeding practices was undertaken during 2010–2011 in Jiangyou, Sichuan Province. Jiangyou is a county-level city with a population of 880 000 located 160 km north of the provincial capital city, Chengdu. Between March and November 2010, a total of 723 mothers who were aged ≥18 years and who delivered single babies at four hospitals and three township health centers in Jiangyou were invited to participate. Women were excluded if they were unable to answer the questions due to limited understanding, illness or deemed unsuitable as advised by health professionals, including doctors, nurses and midwives, at the health facilities. At discharge, a total of 695 eligible women consented to participate (response rate, 96%) and were interviewed face to face by the first author or a trained health facility staff. Follow-up interviews were then conducted at 1, 3 and 6 months postpartum by telephone. The structured baseline and follow-up questionnaires solicited detailed information on sociodemographic and health characteristics, maternal infant feeding intention, maternal satisfaction with infant weight change, infant feeding practices and other data concerning the infant. The questionnaires were taken from those used in our previous studies in Xinjiang and Zhejiang, China, the validity and reliability of which had been verified for Chinese mothers.14,15 By 6 months postpartum, 96 out of 695 mothers (13.8%) were lost to follow up or dropped out of the study: 55 (7.9%) could no longer be reached by telephone, 39 (5.6%) decided not to continue participating, and two (0.3%) were excluded because their infants were severely ill. This project protocol was approved by the Chinese local health authorities and the Human Research Ethics Committee of Curtin University (approval number HR169/2009), and conformed to the provisions of the Declaration of Helsinki. An information letter explaining the project was given and read to each mother before obtaining her written consent. All participants were assured of anonymity and that they could withdraw freely from the study at any time without prejudice.
The 695 participants were aged between 18 and 44 years (median, 24 years). Almost all (99.8%) were married, approximately half received more than 9 years of schooling, and 68.8% of them were employed. Approximately 80% of mothers were delivering their first baby, and 98.4% had a gestation >37 weeks. The infant gender ratio was approximately 1:1, with 94% of birthweight within the range 2.5–4 kg. There were no differences in maternal age, education level, employment status, parity, family monthly income, delivery method, infant gender or infant birthweight between women who completed their participation within 6 months postpartum and those who were lost to follow up (n = 96). In the study, the median age to start complementary feeding was 4.5 months (95% confidence interval [CI]: 4.4–4.6 months). Figure 1 shows the age-specific introduction rates for complementary feeding. Approximately 27% of infants had received complementary foods by the age of 4 months and the rate increased to 90.7% by 6 months. Fruit juice and vegetable juice were the earliest foods introduced to infants in Jiangyou, followed by egg yolk. At 3 months, 14.5% and 1.7% of infants had been given juice and egg yolk, respectively. Three-quarters of the mothers had introduced solid foods to their infants before 6 months postpartum. Table 1 lists the variables that might be expected to have an influence on early introduction of complementary feeding. Univariate Cox regression analysis identified five factors associated with introducing complementary foods prior to 6 months postpartum: maternal education; parity; whether most friends breast-fed their infants; whether infants received formula regularly within the 6 months of life; and the age of the infant when the mother returned to work. Backward stepwise Cox regression analysis (Table 2) confirmed that maternal perception of friends’ breast-feeding behaviors remained as a significant determinant. Mothers who perceived that most friends breast-fed their infants were less likely to initiate complementary feeding before 6 months postpartum (adjusted hazard ratio [HR], 0.70; 95%CI: 0.58–0.84). Returning to employment when the infant was at least 6 months of age was another factor preventing mothers from introducing complementary foods early (adjusted HR, 0.73; 95%CI: 0.58– 0.91). Infants who were fed with infant formula regularly within 6 months, however, were at an elevated risk of receiving complementary foods before 6 months of age (adjusted HR, 1.81; 95%CI: 1.42–2.31).
Statistical analysis
Kaplan–Meier tests were first applied to estimate the median age when complementary foods were introduced. Backward stepwise Cox regression analysis was then conducted to ascertain the determinants of starting complementary feeding before 6 months postpartum. Mothers who completed the 6 month follow-up interview and who did not introduce complementary feeding and those who had not introduced complementary feeding before loss to follow up were the censored observations. The former contributed 6 months of follow up to the Cox regression model and the latter contributed only follow-up time for which they were known to have not introduced complementary feeds. Independent variables considered were chosen from the pertinent literature; they were plausible factors associated with premature complementary feeding and applicable to Chinese mothers residing in Sichuan. Table 1 lists the independent variables used in the Cox regression model. All statistical analysis was performed with IBM SPSS Statistics version 20 (IBM, Armonk, NY, USA).
Discussion Complementary feeding practices documented in the study indicate poor adherence to the WHO recommendations in Jiangyou. Half of the infants had already begun to receive complementary foods by 4.5 months of age. Only one infant remained exclusively breast-fed at age 6 months, and >90% of the infants had received complementary foods. The finding is similar to our previous cohort study in Zhejiang Province, where 95% of infants had been introduced to complementary feeding before 6 © 2014 Japan Pediatric Society
128
L Tang et al.
Table 1 Univariate factors in early introduction of CF (before 6 months of age) Variables Maternal age (years) 3000 Living independently No Yes Parity Primiparous Multiparous Gender of infant Male Female Method of delivery Vaginal delivery Caesarean section Attending antenatal class No Yes Most friends breast-fed their infants No/do not know Yes Intended age of CF introduction Within 6 months After 6 months Do not know Introduction of infant formula within 6 months No Yes Satisfaction with infant weight change Not satisfied/do not know Satisfied Age of infant when mother returned to work
