Associations of age at marriage and first pregnancy with maternal nutritional status in Nepal

Abstract

Background and objectives: Women's nutritional status is important for their health and reproductive fitness. In a population where early marriage is common, we investigated how women's nutritional status is associated with their age at marriage (marking a geographical transfer between households), and at first pregnancy.

Methodology: We used data from a cluster-randomized control trial from lowland Nepal (n = 4071). Outcomes including body mass index (BMI) were measured in early pregnancy and trial endpoint, after delivery. We fitted mixed-effects linear and logistic regression models to estimate associations of age at marriage and age at pregnancy with outcomes, and with odds of chronic energy deficiency (CED, BMI <18.5 kg/m²), at both timepoints.

Results: BMI in early pregnancy averaged 20.9 kg/m², with CED prevalence of 12.5%. In 750 women measured twice, BMI declined 1.2 (95% confidence interval 1.1, 1.3) kg/m² between early pregnancy and endpoint, when CED prevalence was 35.5%. Early pregnancy was associated in dose-response manner with poorer nutritional status. Early marriage was independently associated with poorer nutritional status among those pregnant ≤15 years, but with better nutritional status among those pregnant ≥19 years.

Conclusions and implications: The primary determinant of nutritional status was age at pregnancy, but this association also varied by marriage age. Our results suggest that natal households may marry their daughters earlier if food insecure, but that their nutritional status can improve in the marital household if pregnancy is delayed. Marriage age therefore determines which household funds adolescent weight gain, with implications for Darwinian fitness of the members of both households.

Keywords: child marriage; maternal capital; maternal nutrition; pregnancy; reproductive scheduling.

Figure 1.

Conceptual diagram illustrating how the timing of the transition from the natal to the marital household may shape a woman’s nutritional status, as assessed by BMI. Natal households with lower resources and experiencing food insecurity may have limited capacity to invest in their daughter, which could lead to them marrying her at younger age, and with poor nutritional status. Natal households with greater resources may fund both their daughter’s education and her adolescent increase in BMI, leading to them marrying their daughter at a later age and with better nutritional status. These patterns interact with the daughter’s experience in the marital household, as they may shape both the timing of her pregnancy and her nutritional status when pregnancy occurs. Her nutritional status may continue to improve in the marital household if her pregnancy is delayed. These dynamics affect the fitness of the father, as maternal nutritional status represents a key developmental niche in which his genes are expressed in the offspring

Figure 2.

Interactive associations of nutritional status with age at marriage and age at first pregnancy. (a) Heat map of age at pregnancy and age at marriage for the sample of 4071 women. Twenty percent of the cohort had been married ≤14 years, and 49% had their first pregnancy ≤17 years. (b) Heat map of the time interval (years) between marriage and pregnancy. (c) Plot for BMI. (d) Plot for MUAC. Among those pregnant at ≤15 years, earlier marriage was associated with lower BMI and MUAC (P < 0.05). Among those pregnant at ≥19 years, however, earlier marriage was associated with higher BMI (P < 0.05 for trend)