Adolescent pregnancy and linear growth of infants: a birth cohort study in rural Ethiopia

Abstract

Background: Evidences indicate that the risk of linear growth faltering is higher among children born from young mothers. Although such findings have been documented in various studies, they mainly originate from cross-sectional data and demographic and health surveys which are not designed to capture the growth trajectories of the same group of children. This study aimed to assess the association between young maternal age and linear growth of infants using data from a birth cohort study in Ethiopia.

Methods: A total of 1423 mother-infant pairs, from a birth cohort study in rural Ethiopia were included in this study. They were followed for five time points, with three months interval until the infants were 12 months old. However, the analysis was based on 1378 subjects with at least one additional follow-up measurement to the baseline. A team of data collectors including nurses collected questionnaire based data and anthropometric measurements from the dyads. We fitted linear mixed-effects model with random intercept and random slope to determine associations of young maternal age and linear growth of infants over the follow-up period after adjusting for potential confounders.

Results: Overall, 27.2% of the mothers were adolescents (15-19 years) and the mean ± SD age of the mothers was 20 ± 2 years. Infant Length for Age Z score (LAZ) at birth was negatively associated with maternal age of 15-19 years (β = - 0.24, P = 0.032). However, young maternal age had no significant association with linear growth of the infants over the follow-up time (P = 0.105). Linear growth of infants was associated positively with improved maternal education and iron-folate intake during pregnancy and negatively with infant illness (P < 0.05).

Conclusion: Young maternal age had a significant negative association with LAZ score of infants at birth while its association over time was not influential on their linear growth. The fact that wide spread socio economic and environmental inequalities exist among mothers of all ages may have contributed to the non-significant association between young maternal age and linear growth faltering of infants. This leaves an opportunity to develop comprehensive interventions targeting for the infants to attain optimal catch-up growth.

Keywords: Adolescent pregnancy; Infant growth; Linear growth; Maternal age.

Fig. 1

Flow diagram of follow up of study participants

Fig. 2

Linear growth of infants over 12 months from Mothers of 15–19 years old (---------) and Mothers of 20–24 years (______). Plotted values for the difference from baseline of the repeated measurements are estimated from linear mixed-effects model using random intercept child and random slope time with fixed effects including time, quadratic time, maternal age group, and timeXmaternal age group interactions adjusted for important covariates. The P-value is for group difference on monthly changes of LAZ score over time. β coefficient on monthly changes in LAZ was 0.05; P = 0.179

Fig. 3

linear growth of infants by maternal and infant characteristics: Linear growth and maternal educational status; no formal education (____), primary (---------) and secondary and above (— — —), linear growth and iron and folic acid intake; < 90 days (--------) and ≥ 90 days (_____) and linear growth and infant illness; No (____) and Yes (-------). P-values are for group difference on monthly changes of LAZ score over time. β (95% CI) on monthly changes in LAZ were 0.03 (0.003,0.55); P = 0.024 for Maternal educational status of secondary and above, 0.02 (− 0.01,0.30); P = 0.051for primary maternal educational status, 0.15 (0.02,0.30); P = 0.018for iron-folic acid intake, − 0.15 (− 0.30, − 0.002); P = 0.001 for infant illness