An overall sample of n=5,030 mother-infant dyads with complete anthropometric measures was analysed. Information collected in the survey about EBF (only in infants under 6 months), current BF and predominant BF were available for n=1,338, n=5,030 and n=2,492 subjects respectively (Figure 1). 63.4% of the study population lived in urban areas and 63% were in the lowest socioeconomic group. The mean maternal age was 26.6 years (±6.6) and the mean maternal years of education were 8.4 (±3.9). The majority of the sample were mestizo (72%), not working (59.3%) and living with the partner (75.9%). During pregnancy, 9% consumed alcohol and 2.1% smoked. Caesarean section deliveries accounted for around one-third of the sample (31.4%). The mean birth weight and infants ages were 3.3 kg (±0.5) and 12.1 months (±7.1), respectively. 51.8% of the infants were male (Table 1).
Infant anthropometric status, maternal BMI and breastfeeding practices
The prevalence of wasting, overweight and stunting was 1.5% (n=74/5,030), 5.8% (n=293/5,030) and 12.8% (n=645/5,030) respectively. Mean maternal weight, height and BMI was 59.8 ±12 kg, 1.55 ±0.06 m and 24.8±4.6 kg/m2 respectively. EBF prevalence in infants under 6 months was 34.4%; other infant feeding mode variables analysed were current BF (68%), predominant BF (5.1%), duration of BF (mean=7.9 ± 5.1 months), age of initiation of liquids, semisolids and solids (2.6 ± 2.5 months, 4.9 ± 2.1 months and 7.5 ± 2.5 months, respectively) and formula feeding (42%) (Table 2).
Predictors of wasting
The bivariate analysis showed that wasted infants were more likely not to be currently BF (OR=0.19; 95% CI=0.14, 0.27), to have an earlier age of introduction of liquids (Mean dif.=0.75 months; 95% CI=0.06, 1.45) and a later age of introduction of semisolids (Mean dif.=0.71 months; 95% CI=0.05, 1.37) when compared with infants with normal WLZ. Wasting was not predicted by maternal anthropometry, EBF or predominant BF variables; although there was a trend for infants under 6 months who were not EBF to have a higher prevalence of wasting (n=19, 66.1% in non-EBF vs n=15, 44.1% in EBF). The mean duration of BF was not significantly different between those who were wasted and those who were not (6.9 months v 8.7 months, mean dif.=3.3 months; 95% CI=-0.2, 6.81). Regarding baseline characteristics, infants with wasting had mothers with fewer years of education (Mean dif=1.4; 95% CI=0.31, 2.54), and mothers with lower age (Mean dif=3.39; 95% CI=1.41, 5.37) (Table 2). Wealth index, a potential predictor of wasting, was not significantly associated; however, there was a trend for the poorer/poorest category to have a higher prevalence of wasting when compared with normal WLZ and overweight (n=54, 73% for wasting; n=2,937, 63% for normal WLZ and n=176, 60.1% for overweight)(Table 1). The unadjusted logistic regression model showed that current BF, age of introduction of liquids and semisolids were not significant predictors of wasting. In the final model, the only significant predictor of wasting was fewer years of maternal education (β=-0.09; OR=0.91; 95%CI=0.86, 0.97); however, the model only predicted 0.4% to 1% of wasting in this population (Table 3).
Predictors of overweight
Higher maternal BMI and higher maternal weight were significantly different (Mean dif=1.5 kg/m2; 95% CI=2.1, 0.8 and 4.1 kg; 95% CI=5.8, 2.3, respectively) between infants with normal WLZ and those who were overweight, indicating a positive association between maternal BMI and weight, and infant overweight. Breastfeeding practices and other infant feeding mode variables were not significant predictors (Table 2). Overweight was also associated with more years of maternal education (Mean dif=0.8 years; 95% CI=1.4, 0.25), vaginal delivery (OR=1.49; 95% CI=1.2, 1.9), higher birth weight (Mean dif=0.17 kg; 95% CI=0.25, 0.09) and lower infant age (Mean dif=-1.14 months; 95% CI=-0.12, -2.1) (Table 1).
Higher maternal BMI was significantly related to infant overweight in the unadjusted (β=0.06; OR=1.06; 95% CI=1.03, 1.08), adjusted (β=0.05; OR=1.05; 95% CI=1.02, 1.08) and final model (β=0.05; OR=1.05; 95% CI=1.03, 1.08). The adjusted model showed that more years of maternal education (β=0.06; OR=1.05; 95% CI=1.02, 1.10) and higher birth weight (β=0.001; OR=1.001; 95% CI=1.00, 1.001) were significant independent predictors of overweight, explaining 4% of this category (R2=0.04). However, delivery by caesarean section and infant age were no longer related to overweight (Table 3).
Predictors of stunting
Compared to non-stunted infants, those with stunting had mothers with lower weight (Mean dif.=-4.5 kg; 95% CI=-3. 5, -5.5), shorter height (Mean dif.=-0.04 m; 95% CI=-0.03, -0.04) and lower BMI (Mean dif.=-0.61 kg/m2; 95% CI=-0.22, -0.99); as well as a shorter duration of BF (Mean dif.=-1.33; 95% CI=-2.06, -0.60) and earlier age of initiation of liquids (Mean dif.=-0.61 months; 95% CI=-0.82, -0.40), semisolids (Mean dif.=-0.58 months; 95% CI=-0.77, -0.40) and solids (Mean dif.=-0.61 months; 95% CI=-0.84, -0.38)(Table5). Infants who lived in rural areas (OR=1.74; 95%CI=1.47, 2.05), with lower socioeconomic status (OR=1.96; 95% CI=1.53, 2.49 for poorer/poorest), with a mother with less years of education (Mean dif.=-2.1 years; 95% CI=-1.78, -2.43), belonging to the mestizo ethnic group (OR=2.2; 95% CI=1.85, 2.61), with lower birth weight (Mean dif.=-0.23 kg; 95% CI=-0.17, -0.28), male (OR=1.27; 95% CI=1.08, 1.51) and higher age (Mean dif.=2.34 years; 95% CI=0.29, 2.77) were more likely to be stunted (Table 4). Maternal height, analysed as a continuous variable, was associated with infant stunting after controlling for potential confounders including as type of place of residence, wealth index, ethnicity and infant gender and age (Mean dif=0.09 m; 95% CI=0.8, 0.11; data not shown)
The unadjusted binary logistic model showed that none of the anthropometric and other infant feeding mode variables were related to stunting, apart from a longer duration of BF (β=0.05; OR=1.05; 95% CI=1.02, 1.08). When adjusted for covariates, duration of BF was no longer significant. In the final model, stunted infants had mothers with fewer years of education (β=-0.09; OR=0.92; 95% CI=0.89, 0.94), lower birth weight (β=-0.001; OR=0.99; 95% CI=0.99, 0.99), were female (β=-0.47; OR=0.43; 95% CI=0.49, 0.78) and had higher infant age (β=0.05; OR=1.08; 95% CI=1.03, 1.07)(Table 3). EBF in infants up to 6 months did not predict stunting (OR=0.75, 95% CI=0.14, 1.63; data not shown). The association between infant age and wasting, overweight and stunting was significant in the binary analyses, but only remained significant in the final model for stunting.