Impact of the Korea Early Childhood Home-visiting Intervention

Pregnancy Related Clinical Trial

— KECHI  

Official title:

Impact of the Korea Early Childhood Home-visiting Intervention on Childhood Health and Development and Maternal Health: A Randomized Controlled Community Trial

Clinical Trial Details — Status: Active, not recruiting

Administrative data

• NCT number: NCT04749888
• Other study ID #: C-1911-150-1083
• Secondary ID: KCT0005579HI19C0
• Status: Active, not recruiting
• Phase: N/A
• Start date: October 27, 2021
• Est. completion date: December 31, 2045

Study information

• Verified date: April 2024
• Source: Seoul National University Hospital
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

Maternal and early childhood home visits have been proposed as an effective strategy to improve the health and development of disadvantaged children. In South Korea (hereafter, Korea), a maternal and early childhood home visit program has been implemented since 2013 in Seoul, and then was adopted in 2019 by the central government as a national policy for child health and development. The Korea Early Childhood Home-visiting Intervention (KECHI) encompasses 25-29 home visits, group activities, and community service linkage by social workers from the prenatal period until the child reaches the age of 2 years; as such, it is a complex intervention involving various domains to address a wide range of outcomes. Each home visit is implemented based on the family's needs, and individualized interventions are provided to improve parenting and the home environment in order to promote children's health and development and maternal health. This study is a randomized controlled community trial conducted in Korea to examine the impact of targeted home visits led by nurses in the prenatal and early childhood period on children's health and development and maternal health. This study is a superiority trial with two parallel groups from pregnancy until the child reaches 2 years of age. Pregnant women with two or more risk factors will be recruited to participate in the study after they provide informed consent. Participants will then be randomly assigned to the intervention or control group with a 1:1 allocation through an independent web-based random allocation system. We expect a total of 800 families (400 families in each group) to be recruited. The intervention group will receive the KECHI program and the control group will receive existing maternal and child health services (usual care), but not multiple home visits by nurses. Both groups will receive gift cards of 30,000 Korean won (about 27 USD) for each round of surveys. The intervention and control groups will be surveyed on the outcome variables of home environment, child development, breastfeeding, maternal health, child hospital visits due to injuries, and community service linkage at four home visits by trained research nurses at baseline and at 6 months, 12 months, and 24 months after birth. Telephone contact will also be made at 6 weeks and 18 months after birth for both groups. Outcome measurements will be performed by research nurses and data management will be conducted by statistical analysts. The analysis will be conducted for the intention-to-treat (ITT) and per-protocol (PP) groups, with an interim analysis of outcomes up to the 6-month follow-up. For the primary outcomes and certain secondary outcomes, subgroup analyses will be performed based on factors such as region, fertility status, number of risk factors, presence of depression, education level, etc.

Recruitment information / eligibility

• Status: Active, not recruiting
• Enrollment: 800
• Est. completion date: December 31, 2045
• Est. primary completion date: February 15, 2025
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Female
• Age group: N/A and older

Eligibility

Inclusion Criteria:

• Pregnant women with two or more risk factors at the time of screening
• Pregnant women at less than 37 weeks of gestation
• Pregnant women who can read and answer questionnaires in Korean

Exclusion Criteria:

• Pregnant women who have experienced any critical event such as termination of pregnancy, stillbirth, or child death
• Pregnant women who plan to move abroad or to other regions where the KECHI service is not available within the next 6 months

Related Conditions & MeSH terms

• Child Development
• Infant Development
• Maternal Distress
• Parenting
• Pregnancy Related

Intervention

Behavioral:
• Targeted nurse-led home visiting
The KECHI encompasses 25-29 home visits, group activities, and community service linkage by social workers from the prenatal period until the child reaches the age of 2 years; as such, it is a complex intervention involving various domains to address a wide range of outcomes. Pregnant women with two or more risk factors who are deemed to have difficulties in raising children are eligible for the targeted multiple nurse home visits. Each home visit is implemented based on families' needs, and individualized interventions are provided to improve parenting and the home environment in order to promote the child's health and development and maternal health. The program includes educational materials for parents, such as a booklet covering issues on prenatal care, child development, postnatal child care, parent-child attachment, play, communication, safety, and goal-setting.

Locations

Country	Name	City	State
Korea, Republic of	Institute of Health Policy and Management, Medical Research Center, Seoul National University	Seoul
Korea, Republic of	Medical Research Collaborating Center, Seoul National University Biomedical Research Institute	Seoul

Sponsors (7)

Lead Sponsor	Collaborator
Seoul National University Hospital	Hanyang University, Kangwon National University, National Evidence-Based Healthcare Collaborating Agency, Seoul National University, Soon Chun Hyang University, University of Ulsan

Country where clinical trial is conducted

Korea, Republic of, 

References & Publications (3)

June KJ, Lee JY, Cho SH. Infant Mother's Experiences with the Sustained Nurse Home-Visiting Program. J Korean Soc Matern Child Health. 2021;25(1):31-41.

Khang YH, Cho SH, June KJ, Lee JY, Kim YM, Cho HJ. The Seoul healthy first step project: Introduction and expansion, program content and performance, and future challenges. Journal of the Korean Society of Maternal and Child Health. 2018;22(2):63-76.

Lee JY, June KJ, Cho S-H. Competencies of nurses in a maternal early childhood sustained home-visiting program. Journal of Korean Academy of Community Health Nursing. 2017;28(4):397-409.

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Home environment	Home environment as assessed using IT-HOME (Infant-Toddler Home Observation for Measurement of Environment) when the child is 6 months old. IT-HOME (Infant-Toddler Home Observation for Measurement of Environment), composed of 45 items, was developed by Caldwell & Bradley (1984). The minimum score is 0 and the maximum score is 45, and a higher score means a better outcome.	when the child is 6 months old.
Primary	Home environment	Home environment as assessed using IT-HOME (Infant-Toddler Home Observation for Measurement of Environment) when the child is 12 months old. IT-HOME (Infant-Toddler Home Observation for Measurement of Environment), composed of 45 items, was developed by Caldwell & Bradley (1984). The minimum score is 0 and the maximum score is 45, and a higher score means a better outcome.	when the child is 12 months old.
Primary	Home environment	Home environment as assessed using IT-HOME (Infant-Toddler Home Observation for Measurement of Environment) when the child is 24 months old. IT-HOME (Infant-Toddler Home Observation for Measurement of Environment), composed of 45 items, was developed by Caldwell & Bradley (1984). The minimum score is 0 and the maximum score is 45, and a higher score means a better outcome.	when the child is 24 months old.
Primary	Emergency department visits due to injuries	Number of emergency department visits due to injuries when the child is 6 weeks old.	when the child is 6 weeks old.
Primary	Emergency department visits due to injuries	Number of emergency department visits due to injuries when the child is 6 months old.	when the child is 6 months old.
Primary	Emergency department visits due to injuries	Number of emergency department visits due to injuries when the child is 12 months old.	when the child is 12 months old.
Primary	Emergency department visits due to injuries	Number of emergency department visits due to injuries when the child is 24 months old.	when the child is 24 months old.
Primary	Child development (K-Bayley-III)	Child development as assessed using the K-Bayley-III (Korean Bayley Scales of Infant and Toddler Development-III) score when the child is 24 months old	when the child is 24 months old.
Primary	Breastfeeding duration	Breastfeeding duration when the child is 6 weeks old.	when the child is 6 weeks old.
Primary	Breastfeeding duration	Breastfeeding duration when the child is 6 months old.	when the child is 6 months old.
Primary	Breastfeeding duration	Maternal self-rated health when the child is 12 months old.	when the child is 12 months old.
Primary	Breastfeeding duration	Breastfeeding duration when the child is 24 months old.	when the child is 24 months old.
Primary	Maternal self-rated health	Maternal self-rated health when the child is 6 weeks old.	when the child is 6 weeks old.
Primary	Maternal self-rated health	Maternal self-rated health when the child is 6 months old.	when the child is 6 months old.
Primary	Maternal self-rated health	Maternal self-rated health when the child is 12 months old.	when the child is 12 months old.
Primary	Maternal self-rated health	Maternal self-rated health when the child is 18 months old.	when the child is 18 months old.
Primary	Maternal self-rated health	Maternal self-rated health when the child is 24 months old.	when the child is 24 months old.
Primary	Community service linkage	Community service linkage as measured by the number of community services a mother has received during the last year when the child is 12 months old.	when the child is 12 months old.
Primary	Community service linkage	Community service linkage as measured by the number of community services a mother has received during the last year when the child is 24 months old.	when the child is 24 months old.
Secondary	Safety knowledge	Safety knowledge as measured by the number of questions the mother answered correctly about child accident prevention when the child is 6 months old. The questionnaire testing mothers' safety knowledge is composed of five items from the Korean National Health Insurance Service's Infant Health Examination Questionnaire.	when the child is 6 months old.
Secondary	Safety knowledge	Safety knowledge as measured by the number of questions the mother answered correctly about child accident prevention when the child is 12 months old. The questionnaire testing mothers' safety knowledge is composed of five items from the Korean National Health Insurance Service's Infant Health Examination Questionnaire.	when the child is 12 months old.
Secondary	Safety knowledge	Safety knowledge as measured by the number of questions the mother answered correctly about child accident prevention when the child is 24 months old. The questionnaire testing mothers' safety knowledge is composed of five items from the Korean National Health Insurance Service's Infant Health Examination Questionnaire.	when the child is 24 months old.
Secondary	Emergency department visits	Number of emergency department visits when the child is 6 weeks old.	when the child is 6 weeks old.
Secondary	Emergency department visits	Number of emergency department visits when the child is 6 months old.	when the child is 6 months old.
Secondary	Emergency department visits	Number of emergency department visits when the child is 12 months old.	when the child is 12 months old.
Secondary	Emergency department visits	Number of emergency department visits when the child is 24 months old.	when the child is 24 months old.
Secondary	Hospital admission	Number of hospital admission when the child is 6 weeks old.	when the child is 6 weeks old.
Secondary	Hospital admission	Number of hospital admission when the child is 6 months old.	when the child is 6 months old.
Secondary	Hospital admission	Number of hospital admission when the child is 12 months old.	when the child is 12 months old.
Secondary	Hospital admission	Number of hospital admission when the child is 24 months old.	when the child is 24 months old.
Secondary	Child development (Denver II)	Child development as assessed using Denver (Denver Developmental Screening Test) II when the child is 6 months old.	when the child is 6 months old.
Secondary	Child development (Denver II)	Child development as assessed using Denver (Denver Developmental Screening Test) II when the child is 12 months old.	when the child is 12 months old.
Secondary	Child development (Denver II)	Child development as assessed using Denver (Denver Developmental Screening Test) II when the child is 24 months old.	when the child is 24 months old.
Secondary	Premature birth	Premature birth as assessed by asking the mother whether the child was delivered before 37 weeks.	when the child is 6 weeks old.
Secondary	Delayed growth - height	Height in centimeters measured by a physical examination of the child when the child is 6 months old.	when the child is 6 months old.
Secondary	Delayed growth - height	Height in centimeters measured by a physical examination of the child when the child is 12 months old.	when the child is 12 months old.
Secondary	Delayed growth - height	Height in centimeters measured by a physical examination of the child when the child is 24 months old.	when the child is 24 months old.
Secondary	Delayed growth - weight	Weight in kilograms measured by a physical examination of the child when the child is 6 months old.	when the child is 6 months old.
Secondary	Delayed growth - weight	Weight in kilograms measured by a physical examination of the child when the child is 12 months old.	when the child is 12 months old.
Secondary	Delayed growth - weight	Weight in kilograms measured by a physical examination of the child when the child is 24 months old.	when the child is 24 months old.
Secondary	Delayed growth - head circumference	Head circumference in centimeters measured by a physical examination of the child when the child is 6 months old.	when the child is 6 months old.
Secondary	Delayed growth - head circumference	Head circumference in centimeters measured by a physical examination of the child when the child is 12 months old.	when the child is 12 months old.
Secondary	Delayed growth - head circumference	Head circumference in centimeters measured by a physical examination of the child when the child is 24 months old.	when the child is 24 months old.
Secondary	Knowledge of SIDS (sudden infant death syndrome) prevention	Knowledge of SIDS (sudden infant death syndrome) prevention as measured by the number of questions the mother answered correctly about SIDS prevention when the child is 6 months old. The questionnaire testing the mother's knowledge of SIDS is composed of five items from the Korean National Health Insurance Service's Infant Health Examination Questionnaire.	when the child is 6 months old.
Secondary	Vaccination	Vaccination as assessed by the completion of recommended vaccinations (tuberculosis, hepatitis B, Haemophilus influenzae type b (Hib), DTaP, polio, Streptococcus pneumoniae) when the child is 6 months old.	when the child is 6 months old.
Secondary	Vaccination	Vaccination as assessed by the completion of recommended vaccinations (tuberculosis, hepatitis B, Haemophilus influenzae type b (Hib), DTaP, polio, Streptococcus pneumoniae) when the child is 12 months old.	when the child is 12 months old.
Secondary	Vaccination	Vaccination as assessed by the completion of recommended vaccinations (tuberculosis, hepatitis B, Haemophilus influenzae type b (Hib), DTaP, polio, Streptococcus pneumoniae) when the child is 24 months old.	when the child is 24 months old.
Secondary	National health check-ups	National health check-ups assessed by asking whether the mother has visited a health center or pediatrician for an infant health checkup when the child is 6 months old.	when the child is 6 months old.
Secondary	National health check-ups	National health check-ups assessed by asking whether the mother has visited a health center or pediatrician for an infant health checkup when the child is 12 months old.	when the child is 12 months old.
Secondary	National health check-ups	National health check-ups assessed by asking whether the mother has visited a health center or pediatrician for an infant health checkup when the child is 24 months old.	when the child is 24 months old.
Secondary	Spousal participation in parenting	Spousal participation in parenting as measured by a questionnaire composed of 4 items when the child is 6 months old. The questionnaire was developed by Hong (1995) and used in the Panel Study on Korean Children (PSKC). The minimum score is 4 and the maximum score is 20, and a higher score means a better outcome.	when the child is 6 months old.
Secondary	Spousal participation in parenting	Spousal participation in parenting as measured by a questionnaire composed of 4 items when the child is 12 months old. The questionnaire was developed by Hong (1995) and used in the Panel Study on Korean Children (PSKC). The minimum score is 4 and the maximum score is 20, and a higher score means a better outcome.	when the child is 12 months old.
Secondary	Spousal participation in parenting	Spousal participation in parenting as measured by a questionnaire composed of 4 items when the child is 24 months old. The questionnaire was developed by Hong (1995) and used in the Panel Study on Korean Children (PSKC). The minimum score is 4 and the maximum score is 20, and a higher score means a better outcome.	when the child is 24 months old.
Secondary	Parenting related household expenses	Parenting-related household expenses, which measure a household's expenditures for pregnancy, childbirth, and supplies needed to care for the child when the child is 6 months old.	when the child is 6 months old.
Secondary	Parenting related household expenses	Parenting-related household expenses, which measure a household's expenditures for pregnancy, childbirth, and supplies needed to care for the child when the child is 12 months old.	when the child is 12 months old.
Secondary	Parenting related household expenses	Parenting-related household expenses, which measure a household's expenditures for pregnancy, childbirth, and supplies needed to care for the child when the child is 24 months old.	when the child is 24 months old.
Secondary	Intention to have another child	Intention to have another child as assessed by a single question, "Do you have any intention to have more children in the future?". Responses to this question are categorized into three options: "Yes, I have the intention to have another child", "No, I don't have the intention to have another child", and "I don't know."	when the child is 24 months old.
Secondary	Experience of delivery in the past 2 years	Experience of delivery in the past 2 years as assessed by using a single question: "Have you had the experience of subsequent childbirth (having another child after participating in the study) or are you currently pregnant?" Responses to this question are categorized into three options: "Yes, I have had subsequent childbirth experience," "Yes, I am currently pregnant," and "No, I don't have subsequent childbirth."	when the child is 24 months old.
Secondary	Depression (EPDS)	Depression as assessed using the EPDS (Edinburgh Postnatal Depression Scale) when the child is 6 months old. The EPDS (Edinburgh Postnatal Depression Scale) was developed by Cox et al. (1987) as a tool measuring postnatal depression. It is composed of 10 items. The minimum score is 0 and the maximum score is 30, and a higher score means a worse outcome.	when the child is 6 months old.
Secondary	Depression (EPDS)	Depression as assessed using the EPDS (Edinburgh Postnatal Depression Scale) when the child is 12 months old. The EPDS (Edinburgh Postnatal Depression Scale) was developed by Cox et al. (1987) as a tool measuring postnatal depression. It is composed of 10 items. The minimum score is 0 and the maximum score is 30, and a higher score means a worse outcome.	when the child is 12 months old.
Secondary	Depression (EPDS)	Depression as assessed using the EPDS (Edinburgh Postnatal Depression Scale) when the child is 24 months old. The EPDS (Edinburgh Postnatal Depression Scale) was developed by Cox et al. (1987) as a tool measuring postnatal depression. It is composed of 10 items. The minimum score is 0 and the maximum score is 30, and a higher score means a worse outcome.	when the child is 24 months old.
Secondary	Suicidal ideation	Suicidal ideation as assessed using the 10th item of EPDS (Edinburgh Postnatal Depression Scale) when the child is 6 months old. The EPDS (Edinburgh Postnatal Depression Scale) was developed by Cox et al. (1987) as a tool measuring postnatal depression and the 10th item of EPDS asks respondents to indicate how often they have experienced thoughts of self harm using a 4-point frequency scale.	when the child is 6 months old.
Secondary	Suicidal ideation	Suicidal ideation as assessed using the 10th item of EPDS (Edinburgh Postnatal Depression Scale) when the child is 12 months old. The EPDS (Edinburgh Postnatal Depression Scale) was developed by Cox et al. (1987) as a tool measuring postnatal depression and the 10th item of EPDS asks respondents to indicate how often they have experienced thoughts of self harm using a 4-point frequency scale.	when the child is 12 months old.
Secondary	Suicidal ideation	Suicidal ideation as assessed using the 10th item of EPDS (Edinburgh Postnatal Depression Scale) when the child is 24 months old. The EPDS (Edinburgh Postnatal Depression Scale) was developed by Cox et al. (1987) as a tool measuring postnatal depression and the 10th item of EPDS asks respondents to indicate how often they have experienced thoughts of self harm using a 4-point frequency scale.	when the child is 24 months old.
Secondary	Depression (PHQ-9)	Depression as assessed using the PHQ-9 (Patient Health Questionnaire-9) when the child is 6 months old. The PHQ-9 (Patient Health Questionnaire-9) was developed by Kroenke, K. et al. (2001) as a tool measuring the depression level of adults and composed of 9 items. The minimum score is 0 and the maximum score is 27, and higher score means a worse outcome.	when the child is 6 months old.
Secondary	Depression (PHQ-9)	Depression as assessed using the PHQ-9 (Patient Health Questionnaire-9) when the child is 12 months old. The PHQ-9 (Patient Health Questionnaire-9) was developed by Kroenke, K. et al. (2001) as a tool measuring the depression level of adults and composed of 9 items. The minimum score is 0 and the maximum score is 27, and higher score means a worse outcome.	when the child is 12 months old.
Secondary	Depression (PHQ-9)	Depression as assessed using the PHQ-9 (Patient Health Questionnaire-9) when the child is 24 months old. The PHQ-9 (Patient Health Questionnaire-9) was developed by Kroenke, K. et al. (2001) as a tool measuring the depression level of adults and composed of 9 items. The minimum score is 0 and the maximum score is 27, and higher score means a worse outcome.	when the child is 24 months old.
Secondary	Depression (Whooley & Arroll questions)	Maternal depression as assessed using the Whooley & Arroll questions when the child is 6 weeks old. To screen depression in outpatient settings, a simple tool called " two screening questions" was developed. Arroll B. et al. (2005) enhanced the sensitivity and specificity of the tool by adding a "help-seeking question". If the response to at least one of the Screening 2-Item questions is affirmative or if the response to the help-seeking question is affirmative, further evaluation is necessary.	when the child is 6 weeks old.
Secondary	Depression (Whooley & Arroll questions)	Maternal depression as assessed using the Whooley & Arroll questions when the child is 18 months old. To screen depression in outpatient settings, a simple tool called " two screening questions" was developed. Arroll B. et al. (2005) enhanced the sensitivity and specificity of the tool by adding a "help-seeking question". If the response to at least one of the Screening 2-Item questions is affirmative or if the response to the help-seeking question is affirmative, further evaluation is necessary.	when the child is 18 months old.
Secondary	Anxiety	Anxiety level as assessed using the GAD-2 (Generalized Anxiety Disorder 2-item) when the child is 6 months old. The GAD-2 (Generalized Anxiety Disorder 2-item) is a 2-item questionnaire that measures core anxiety symptoms. The minimum score is 0 and the maximum score is 6, and higher score means a worse outcome.	when the child is 6 months old.
Secondary	Anxiety	Anxiety level as assessed using the GAD-2 (Generalized Anxiety Disorder 2-item) when the child is 12 months old. The GAD-2 (Generalized Anxiety Disorder 2-item) is a 2-item questionnaire that measures core anxiety symptoms. The minimum score is 0 and the maximum score is 6, and higher score means a worse outcome.	when the child is 12 months old.
Secondary	Anxiety	Anxiety level as assessed using the GAD-2 (Generalized Anxiety Disorder 2-item) when the child is 24 months old. The GAD-2 (Generalized Anxiety Disorder 2-item) is a 2-item questionnaire that measures core anxiety symptoms. The minimum score is 0 and the maximum score is 6, and higher score means a worse outcome.	when the child is 24 months old.
Secondary	Maternal tobacco use	Maternal tobacco use assessed by current tobacco use status when the child is 6 months old. Maternal tobacco use is assessed by questioning the participants about their current tobacco use behavior during the month before the study.	when the child is 6 months old.
Secondary	Maternal tobacco use	Maternal tobacco use assessed by current tobacco use status when the child is 12 months old. Maternal tobacco use is assessed by questioning the participants about their current tobacco use behavior during the month before the study.	when the child is 12 months old.
Secondary	Maternal tobacco use	Maternal tobacco use assessed by current tobacco use status when the child is 24 months old. Maternal tobacco use is assessed by questioning the participants about their current tobacco use behavior during the month before the study.	when the child is 24 months old.
Secondary	Maternal alcohol consumption	Maternal alcohol consumption when the child is 6 months old. Maternal alcohol consumption is assessed by questioning the participants about their drinking behavior during the month before the study.	when the child is 6 months old.
Secondary	Maternal alcohol consumption	Maternal alcohol consumption when the child is 12 months old. Maternal alcohol consumption is assessed by questioning the participants about their drinking behavior during the month before the study.	when the child is 12 months old.
Secondary	Maternal alcohol consumption	Maternal alcohol consumption when the child is 24 months old. Maternal alcohol consumption is assessed by questioning the participants about their drinking behavior during the month before the study.	when the child is 24 months old.
Secondary	Delivery type	Delivery type as assessed by asking a mother to choose her delivery type between "normal delivery," "planned C-section," and "unplanned emergency C-section" when the child is 6 weeks old.	when the child is 6 weeks old.
Secondary	Maternal parenting stress	Maternal parenting stress as assessed using the Being a Mother Scale (BaM-13) when the child is 6 months old. The Being a Mother Scale (BaM-13) was developed by Matthey (2011) for assessing mothers' level of distress. It is composed of 13 items. The minimum score is 0 and the maximum score is 39, and a higher score means a high level of distress.	when the child is 6 months old.
Secondary	Maternal parenting stress	Maternal parenting stress as assessed using the Being a Mother Scale (BaM-13) when the child is 12 months old. The Being a Mother Scale (BaM-13) was developed by Matthey (2011) for assessing mothers' level of distress. It is composed of 13 items. The minimum score is 0 and the maximum score is 39, and a higher score means a high level of distress.	when the child is 12 months old.
Secondary	Maternal parenting stress	Maternal parenting stress as assessed using the Being a Mother Scale (BaM-13) when the child is 24 months old. The Being a Mother Scale (BaM-13) was developed by Matthey (2011) for assessing mothers' level of distress. It is composed of 13 items. The minimum score is 0 and the maximum score is 39, and a higher score means a high level of distress.	when the child is 24 months old.
Secondary	Intimate partner violence	Intimate partner violence as assessed using the HITS (Hurt, Insult, Threaten, and Scream) tool when the child is 6 months old. The HITS (Hurt, Insult, Threaten, and Scream) tool was developed by Sherin et al. (1998) for assessing the level of domestic violence. It is composed of 4 items. The minimum score is 4 and the maximum score is 20, and higher score means a high level of domestic violence.	when the child is 6 months old.
Secondary	Intimate partner violence	Intimate partner violence as assessed using the HITS (Hurt, Insult, Threaten, and Scream) tool when the child is 12 months old. The HITS (Hurt, Insult, Threaten, and Scream) tool was developed by Sherin et al. (1998) for assessing the level of domestic violence. It is composed of 4 items. The minimum score is 4 and the maximum score is 20, and higher score means a high level of domestic violence.	when the child is 12 months old.
Secondary	Intimate partner violence	Intimate partner violence as assessed using the HITS (Hurt, Insult, Threaten, and Scream) tool when the child is 24 months old. The HITS (Hurt, Insult, Threaten, and Scream) tool was developed by Sherin et al. (1998) for assessing the level of domestic violence. It is composed of 4 items. The minimum score is 4 and the maximum score is 20, and higher score means a high level of domestic violence.	when the child is 24 months old.
Secondary	Maternal body weight	Maternal body weight when the child is 6 weeks old.	when the child is 6 weeks old.
Secondary	Maternal body weight	Maternal body weight when the child is 6 months old.	when the child is 6 months old.
Secondary	Maternal body weight	Maternal body weight when the child is 12 months old.	when the child is 12 months old.
Secondary	Maternal body weight	Maternal body weight when the child is 24 months old.	when the child is 24 months old.
Secondary	Social support	Social support as measured by a questionnaire developed by the Korea Institute of Child Care and Education when the child is 6 months old. The questionnaire measuring social support developed and used by Korea Institute of Child Care and Education is composed of 12 items. The minimum score is 12 and the maximum score is 60, and a higher score means a better outcome.	when the child is 6 months old.
Secondary	Social support	Social support as measured by a questionnaire developed by the Korea Institute of Child Care and Education when the child is 12 months old. The questionnaire measuring social support developed and used by Korea Institute of Child Care and Education is composed of 12 items. The minimum score is 12 and the maximum score is 60, and a higher score means a better outcome.	when the child is 12 months old.
Secondary	Social support	Social support as measured by a questionnaire developed by the Korea Institute of Child Care and Education when the child is 24 months old. The questionnaire measuring social support developed and used by Korea Institute of Child Care and Education is composed of 12 items. The minimum score is 12 and the maximum score is 60, and a higher score means a better outcome.	when the child is 24 months old.
Secondary	Food insecurity	Food insecurity assessed by asking about the family's level of limited access to adequate food over the past year when the child is 12 months.	when the child is 12 months old.
Secondary	Food insecurity	Food insecurity assessed by asking about the family's level of limited access to adequate food over the past year when the child is 24 months.	when the child is 24 months old.
Secondary	Spousal intimacy	Spousal intimacy as measured using the Revised-Kansas Marital Satisfaction Scale modified by the Korea Institute of Child Care and Education when the child is 6 months old. The Revised-Kansas Marital Satisfaction Scale modified by the Korea Institute of Child Care and Education is composed of 4 items. The minimum score is 4 and the maximum score is 20, and higher score means a better outcome.	when the child is 6 months old.
Secondary	Spousal intimacy	Spousal intimacy as measured using the Revised-Kansas Marital Satisfaction Scale modified by the Korea Institute of Child Care and Education when the child is 12 months old. The Revised-Kansas Marital Satisfaction Scale modified by the Korea Institute of Child Care and Education is composed of 4 items. The minimum score is 4 and the maximum score is 20, and higher score means a better outcome.	when the child is 12 months old.
Secondary	Spousal intimacy	Spousal intimacy as measured using the Revised-Kansas Marital Satisfaction Scale modified by the Korea Institute of Child Care and Education when the child is 24 months old. The Revised-Kansas Marital Satisfaction Scale modified by the Korea Institute of Child Care and Education is composed of 4 items. The minimum score is 4 and the maximum score is 20, and higher score means a better outcome.	when the child is 24 months old.
Secondary	Spousal tobacco use	Spousal tobacco use assessed by current tobacco use status when the child is 6 months old. Spouse tobacco use is assessed by questioning participants about their spouse's current tobacco use behavior during the month before the study.	when the child is 6 months old.
Secondary	Spousal tobacco use	Spousal tobacco use assessed by current tobacco use status when the child is 12 months old. Spouse tobacco use is assessed by questioning participants about their spouse's current tobacco use behavior during the month before the study.	when the child is 12 months old.
Secondary	Spousal tobacco use	Spousal tobacco use assessed by current tobacco use status when the child is 24 months old. Spouse tobacco use is assessed by questioning participants about their spouse's current tobacco use behavior during the month before the study.	when the child is 24 months old.
Secondary	Spousal alcohol consumption	Spousal alcohol consumption when the child is 6 months old. Spouse alcohol consumption is assessed by questioning participants about their spouse's drinking behavior during the month before the study.	when the child is 6 months old.
Secondary	Spousal alcohol consumption	Spousal alcohol consumption when the child is 12 months old. Spouse alcohol consumption is assessed by questioning participants about their spouse's drinking behavior during the month before the study.	when the child is 12 months old.
Secondary	Spousal alcohol consumption	Spousal alcohol consumption when the child is 24 months old. Spouse alcohol consumption is assessed by questioning participants about their spouse's drinking behavior during the month before the study.	when the child is 24 months old.
Secondary	Parent-child interaction	Parent-child interaction as assessed by using the NCAST (Nursing Child Assessment Teaching Scale) when the child is 12 months old. The NCAST (Nursing Child Assessment Teaching Scale) was developed by Barnard (1989) for assessing parent-child interaction. It is composed of 73 items that measure sensitivity to cues, response to child's distress, cognitive growth fostering, clarity of cues, and responsiveness to caregiver. The minimum score is 0 and the maximum score is 105, and a higher score means a better outcome.	when the child is 12 months old.
Secondary	Parent-child interaction	Parent-child interaction as assessed by using the NCAST (Nursing Child Assessment Teaching Scale) when the child is 24 months old. The NCAST (Nursing Child Assessment Teaching Scale) was developed by Barnard (1989) for assessing parent-child interaction. It is composed of 73 items that measure sensitivity to cues, response to child's distress, cognitive growth fostering, clarity of cues, and responsiveness to caregiver. The minimum score is 0 and the maximum score is 105, and a higher score means a better outcome.	when the child is 24 months old.