Table 1 Operational definition and categorisation of selected explanatory variables for both NDHS 2006 and NDHS 2011

Development regions (Administrative)

Developmental regions (1 = Far-Western; 2 = Mid-Western; 3 = Western; 4 = Central; 5 = Eastern)

Ecological regions

Ecologically defined area. Division according to ecological zone (3 = Mountain; 2 = Hill; 1 = Terai)

Residence

Residence type (1 = Urban; 2 = Rural)

Antenatal care visits in the cluster

Any antenatal care service received by mother during pregnancy (0 = Yes; 1 = No)

Delivery assisted by trained health workers in the cluster

Birth assistance during delivery in the cluster (0 = Yes/Some; 1 = No/None)

Postnatal check-up/care received by mothers in the cluster

Postnatal check-up by mothers after delivery (0 = Yes; 1 = No)

Maternal education

Maternal formal years of schooling/education (0 = No education; 1 = primary; 2 = secondary; 3 = Higher)

Paternal education

Father’s formal years of schooling/education (0 = No education; 1 = primary; 2 = secondary; 4 = Higher)

Religion

Religion of parents (1 = Hindu; 2 = Buddhist; 3 = Muslim; 4 = Christian/Kirat/other)

Maternal literacy

Mother’s literacy level (1 = able to read whole sentence or only parts; 2 = unable to read at all)

Paternal occupation

Father’s employment status (0 = Unemployed; 1 = Employed; 2 = Don’t know)

Maternal occupation

Mother’s employment status (0 = Unemployed; 1 = employed)

Wealth index

Household index of amenities/families economic status (1 = Poorest; 2 = Poorer; 3 = Middle; 4 = Richer; 5 = Richest)

Biomass use (cooking fuel)

Types of cooking fuel used in the family (1 = relatively non-polluting; 2 = relatively high polluting)

Mother’s age at child birth

Maternal age at childbirth as categorical variable (1 = ≤16 years; 2 = 17–21 years; 3 = ≥22 years)

Mother’s age at marriage

Maternal age at first marriage as categorical variable (1 = ≤16 years; 2 = 17–21 years; 3 = ≥22 years)

Maternal Marital Status

Maternal marital status (0 = never married; 1 = Currently married; 2 = Widowed; 3 = Divorced/Separated)

Decision making on own health care need

Decision making capacity of mothers on her own health care needs (1 = Respondent alone; 2 = Respondent and husband/partner/other; 3 = Husband/partner alone; 4 = Someone else)

Decision making capacity on money expenditure

Decision making capacity of mothers on money expenditure. (1 = Respondent alone; 2 = Respondent and husband/partner/other; 3 = Husband/partner alone; 4 = Someone else)

Maternal BMI (kg/m²)

Maternal BMI as per WHO classification (1 = Underweight (<18.50); 2 = Normal range (18.50–24.99); 3 = Overweight/Obese- at risk (>25.0)

^aMaternal BMI Asian (1 = Underweight (<18.49); 2 = Normal range (18.5–24.99); 3 = Overweight/Obese- at risk (>25.0)

Sex of child

Sex of infant (0 = Male; 1 = Female)

Birth order/rank

Birth rank of infant as a categorical variable (1 = 1^st birth rank; 2 = 2^nd or 3^rd birth rank; 3 = ≥4^th birth rank)

Birth interval

Succeeding birth interval (0 = ≤24 months; 1= > 24 months)

Preceding birth interval (0 = ≤24 months; 1= > 24 months)

Baby’s size at birth (Birth size defined by baby’s birth weight)

Subjective assessment of the respondent on the baby’s birth size (1 = very large/larger than average (>3000 g); 2 = average (2500 to 3000 gm); 3 = very small/smaller than average (<2500 g))

Place of delivery

Delivery place (0 = Home; 1 = Health Facility)

Mode of delivery

Mode of delivery (1 = Non-caesarean section/Normal/vaginal; 2 = caesarean section)

Delivery assistant by

Type of delivery assistance (1 = Professionals (Doctors, Nurses and Midwives; 2-Traditional births attendants (TBAs); 3 = combined; 4 = No assistance)

Currently Breastfeeding

Breastfeeding status during the time of interview (1 = yes; 2 = No)