1344Interbirth interval and maternal anaemia in 21 sub-Saharan African countries: a multinational cross-sectional study

Background Anaemia is a global public health problem, which disproportionately affects women in sub-Saharan Africa (SSA). The causes of anaemia are multifactorial, and a short interbirth interval has been identified as a potentially modifiable risk factor. However, the current evidence for the association between interbirth interval and maternal anaemia remains inconclusive. Hence, this study aimed at examining the association between the interbirth interval and maternal anaemia in SSA. Methods We conducted a multinational cross-sectional study of interbirth interval (time between two singleton live births) and maternal anaemia for 21 SSA countries using the most recent nationally representative Demographic and Health Surveys, 2010-2017. Modified Poisson regression models were used to estimate the relative risk (RR) and 95% confidence intervals (CIs) after adjusting for confounding variables. Results There were 81,693 women included in the study (89.2% nonpregnant, 10.8% pregnant and 32.2% postpartum). Overall, 36.9% of women had anaemia (36.0% of non-pregnant, 44.3% pregnant, and 38.7% of postpartum women). Compared to a 24-35 months interbirth interval, maternal anaemia was not associated with short (<24 months) interbirth intervals (aRR 1.01, 95% CI; 0. 98, 1.04) or long (≥60 months) interbirth interval (aRR 1.00, 95% CI 0.96, 1. 04). Conclusions Our finding revealed insufficient evidence that both short and long birth intervals were associated with the risk of maternal anaemia in SSA. Key messages It is unlikely that the high prevalence of maternal anaemia in SSA can be reduced by avoiding short nor long interbirth intervals.

A model of the evolution of equitable offers in n-person dictator games with interbirth intervals

People are often generous even when it is not in their apparent self-interest to do so as demonstrated by numerous experiments using the dictator game (DG). More recent research using DGs has varied the number of dictators and recipients and used these games to investigate the bystander effect and congestible altruism. These studies have found that people are less generous when there are others who could be generous (the bystander effect) and also less generous when there are multiple recipients (congestible altruism) though the sum of their generosity to all recipients increases. A working hypothesis is proposed that the context-sensitive generosity observed in n-person DGs can be explained as equitable behavior. From an evolutionary perspective, explaining the evolution of equitable behavior is challenging at best. To provide an evolutionary explanation, a second working hypothesis is proposed: equitable offers evolve because they reduce resource deficits produced by variability in the accumulation of resources and thereby minimize the length of interbirth intervals (IBIs) and increase fitness. Based on this working hypothesis, an evolutionary model was developed for n-person DGs to investigate the evolution of equitable offers as a resource allocation problem when reproduction is constrained by IBIs. Simulations demonstrated that equitable offers could evolve in group-structured populations when there is a cost (i.e., longer IBIs) to running resource deficits. Mean evolved offers also varied as a function of the number of dictators and recipients in patterns consistent with the bystander effect and congestible altruism. Equitable offers evolved because they reduced resource variability among group members and thereby reduced resource deficits, which insured higher average rates of reproduction for more equitable groups of agents. Implications of these results are discussed.

Interpregnancy and interbirth intervals and all-cause, cardiovascular-related and cancer-related maternal mortality: findings from a large population-based cohort study

IntroductionScarce research is available regarding the association between interbirth intervals (IBI) and long-term maternal health outcomes, particularly cardiovascular disease (CVD) mortality. We aimed to assess whether IBIs were associated with all-cause, CVD-related and cancer-related mortality.MethodsWe conducted a cohort study in the setting of the Jerusalem Perinatal Study. Women with at least two consecutive singleton live births in 1964–1976 (N=18 294) were followed through 2016. IBIs were calculated as the interval between women’s first and second cohort birth. We estimated associations between IBIs and mortality using Cox’s proportional hazards models, adjusting for age, parity, maternal education, maternal origin and paternal socioeconomic status. Date of last menstrual period was available for a subset of women. We assessed the interpregnancy interval (IPI) for these women and compared the models using IPI and IBI.ResultsDuring 868 079 years of follow up (median follow-up: 49.0 years), 3337 women died. Women with IBIs <15 months had higher all-cause mortality rates (HR 1.18; 95% CI 1.05 to 1.33) compared to women with 33-month to 68-month IBIs (reference category). IBI and CVD mortality appeared to have a J-shaped association; IBIs of <15, 15–20, 21–2626–2632, 33–68 and ≥69 months had HRs of 1.44, 1.40, 1.33, 1.14, 1.00 and 1.30, respectively. No substantial association was found with cancer mortality. Models using IPIs and those using IBI were similar.ConclusionOur results support the WHO recommendations for IPIs of ≥24 months and add additional evidence regarding long-term CVD mortality.

Examining internal migration effects on short versus long interbirth intervals in Cotonou, Benin Republic

Background The literature on migration-fertility relationship uses various measures of fertility, such as fertility rates, actual fertility and family size preferences. This study introduces a different measure—interbirth intervals over women’s reproductive years—to examine how internal migration is associated with short interbirth intervals (less than 24 months) and long interbirth intervals (greater than 60 months) in Cotonou, the largest city of Benin Republic. Methods The paper uses primary data on 2852 live births to 1659 women aged 15–49 years from the 2018 Fertility and Migration Survey in Cotonou. Competing-risks models were fitted for the analysis. Results Nineteen percent of live births were of short interbirth intervals and 16% were of long interbirth intervals. The prevalence of short interbirth intervals was higher among migrants who spent less than 5 years in Cotonou (29%) than among non-migrants (19%) and earlier migrants (18%). Non-migrants had the highest proportion of long interbirth intervals (19%). Within the first 5 years following the migration to Cotonou, migrants had higher subhazard ratio (SHR) of short interbirth intervals (SHR: 1.71, 95% CI: 1.33–2.21) and lower SHR of long interbirth intervals (SHR: 0.64, 95% CI: 0.47–0.87) than non-migrants. This association holds after controlling for socioeconomic characteristics—but with a slightly reduced gap between migrants who spent less than 5 years in Cotonou and non-migrants. Afterwards and irrespective of women’s socioeconomic backgrounds, migrants who spent 5 or more years in Cotonou and non-migrants had similar risks of short and long interbirth intervals. Finally, from 5 years of stay in Cotonou, migrants for reasons other than school or job were less likely to experience short interbirth intervals (SHR: 0.65, 95% CI: 0.46–0.98 for migrants who spent 5–10 years in Cotonou, and SHR: 0.74, 95% CI: 0.54–1.02 for migrants who spent more than 10 years in Cotonou) than non-migrants. Conclusion Family planning programmes should mainly target migrants in the early years after their arrival in Cotonou. Moreover, non-migrants need to be sensitised on the adverse health outcomes of long interbirth intervals.

Labor Curves in Multiparous Women Related to Interbirth Intervals

Objective Previous studies have shown that risk of cesarean section increases among multiparous women as interbirth interval increases. One possibility is that progress of labor may vary with interbirth interval, such that with longer intervals, labor curves of multiparas more closely resemble those of nulliparas. We sought to define labor curves among a cohort of multiparas with varying interbirth intervals. Study Design This was a retrospective cohort study of term multiparas with known interval from last delivery and only vaginal deliveries. Subjects were grouped by interval between the studied pregnancy and the most recent birth: 0 to 59, 60 to 119, and ≥120 months. Statistical analysis was performed using linear mixed effects model. Group slopes and intercepts were compared using model t-tests for individual effects. Length of second stage was compared using a Wilcoxon's rank-sum test. Results Groups did not differ significantly in demographic or obstetrical characteristics. Rate of dilation was similar between the 0 to 59 and 60 to 119 month groups (p = 0.38), but faster in the ≥120 month group compared with the 60 to 119 month group (p = 0.037). Median duration of second stage increased slightly with increased interbirth interval (p = 0.003). Conclusion Prolonged interbirth interval is not associated with slower active phase of labor.