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We analysed population data from the 2015–16 National Family Health Survey to disentangle the intricate underlying effects of reproductive behaviours and fertility preferences on child growth. We expected birth interval length to be more strongly associated with stunting than sibsize and these effects to be moderated by whether the child was wanted or unintended (mistimed/unwanted). Regression analyses showed strong and equal effects of short birth interval and sibsize on stunting, when adjusted for potential confounders and unobserved between-mother heterogeneity. There were no statistical associations between stunting and mistiming/unwantedness of index children, suggesting the absence of discrimination against such children. We conclude that while fertility preferences have no effect, reproductive behaviours exert significant influence on child growth. Sibsize has been falling for many years in India but birth interval lengths have remained largely unchanged. The results underscore the need for strengthening uptake of reversible contraceptives to enable longer birth intervals. [ABSTRACT FROM AUTHOR]

Background: Recent steep declines in child mortality have been attributed in part to increased use of contraceptives and the resulting change in fertility behaviour, including an increase in the time between births. Previous observational studies have documented strong associations between short birth spacing and an increase in the risk of neonatal, infant, and under-five mortality, compared to births with longer preceding birth intervals. In this analysis, we compare two methods to estimate the association between short birth intervals and mortality risk to better inform modelling efforts linking family planning and mortality in children. Objectives: Our goal was to estimate the mortality risk for neonates, infants, and young children by preceding birth space using household survey data, controlling for mother-level factors and to compare the results to those from previous analyses with survey data. Design: We assessed the potential for confounding when estimating the relative mortality risk by preceding birth interval and estimated mortality risk by birth interval in four categories-less than 18 months, 18-23 months, 24-35 months, and 36 months or longer. We estimated the relative risks among women who were 35 and older at the time of the survey with two methods- in a Cox proportional hazards regression adjusting for potential confounders and also by stratifying Cox regression by mother, to control for all factors that remain constant over a woman's childbearing years. We estimated the overall effects for birth spacing in a meta-analysis with random survey effects. Results: We identified several factors known for their associations with neonatal, infant, and child mortality that are also associated with preceding birth interval. When estimating the effect of birth spacing on mortality, we found that regression adjustment for these factors does not substantially change the risk ratio for short birth intervals compared to an unadjusted mortality ratio. For birth intervals less than 18 months, standard regression adjustment for confounding factors estimated a risk ratio for neonatal mortality of 2.28 (95% confidence interval- 2.18-2.37). This same effect estimated within mother is 1.57 (95% confidence interval- 1.52-1.63), a decline of almost one-third in the effect on neonatal mortality. Conclusions: Neonatal, infant, and child mortality are strongly and significantly related to preceding birth interval, where births within a short interval of time after the previous birth have increased mortality. Previous analyses have demonstrated this relationship on average across all births; however, women who have short spaces between births are different from women with long spaces. Among women 35 years and older where a comparison of birth spaces within mother is possible, we find a much reduced although still significant effect of short birth spaces on child mortality. [ABSTRACT FROM AUTHOR]

Seasonal patterns of five measures of reproduction in a population of married women are considered: marital fertility rate, pregnancy prevalence, mean open birth interval, mean closed birth interval-birth, and mean closed birth interval-woman. In a model the fertility rate is assumed to follow a known trigonometric curve; then the lag and relative variability of the other measures are considered in comparison with the fertility rate curve. The predictions from this theoretical work, when compared with observed patterns and trigonometric regression results for each measure in data from Bangladesh, are shown to be quite accurate. Implications for fertility analyses are discussed. [ABSTRACT FROM AUTHOR]