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The evolutionary dynamics of timing of maternal immunity: evaluating the role of age-specific mortality.

ABSTRACT: If a female survives an infection, she can transfer antibodies against that particular pathogen to any future offspring she produces. The resulting protection of offspring for a period after their birth is termed maternal immunity. Because infection in newborns is associated with high mortality, the duration of this protection is expected to be under strong selection. Evolutionary modelling structured around a trade-off between fertility and duration of maternal immunity has indicated selection for longer duration of maternal immunity for hosts with longer lifespans. Here, we use a new modelling framework to extend this analysis to consider characteristics of pathogens (and hosts) in further detail. Importantly, given the challenges in characterizing trade-offs linked to immune function empirically, our model makes no assumptions about costs of longer lasting maternal immunity. Rather, a key component of this analysis is variation in mortality over age. We found that the optimal duration of maternal immunity is shaped by the shifting balance of the burden of infection between young and old individuals. As age of infection depends on characteristics of both the host and the pathogen, both affect the evolution of duration of maternal immunity. Our analysis provides additional support for selection for longer duration of maternal immunity in long-lived hosts, even in the absence of explicit costs linked to duration of maternal immunity. Further, the scope of our results provides explanations for exceptions to the general correlation between duration of maternal immunity and lifespan, as we found that both pathogen characteristics and trans-generational effects can lead to important shifts in fitness linked to maternal immunity. Finally, our analysis points to new directions for quantifying the trade-offs that drive the development of the immune system.

SUBMITTER: Metcalf CJ

PROVIDER: S-EPMC6776077 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature

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The evolutionary dynamics of timing of maternal immunity: evaluating the role of age-specific mortality.

Metcalf C J E CJ Jones J H JH

Journal of evolutionary biology 20150226 2

If a female survives an infection, she can transfer antibodies against that particular pathogen to any future offspring she produces. The resulting protection of offspring for a period after their birth is termed maternal immunity. Because infection in newborns is associated with high mortality, the duration of this protection is expected to be under strong selection. Evolutionary modelling structured around a trade-off between fertility and duration of maternal immunity has indicated selection ...[more]

PMID: 25611057

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Project description:BackgroundDespite improvements in many health indicators, maternal mortality has plateaued in Bangladesh. Achieving the global target of reductions in maternal mortality and the associated Sustainable Development Goals will not be possible without actions to prevent deaths due to preeclampsia/eclampsia. Here we examined the levels, trends, specific causes, timing, place, and care-seeking behaviours of women who died due to these two causes.MethodsWe used nationally representative Bangladesh Maternal Mortality and Health Care Surveys (BMMSs) conducted in 2001, 2010, and 2016 to examine levels and trends of deaths due to preeclampsia/eclampsia. We based the analysis of specific causes, timing, and place of preeclampsia/eclampsia deaths, and care seeking before the deaths on 41 such deaths captured in the 2016 survey. We also used BMMS 2016 survey verbal autopsy (VA) questionnaire to highlight stories that put faces to the numbers.ResultsThe preeclampsia/eclampsia-specific mortality ratio decreased from 77 per 100 000 live births in the 2001 BMMS to 40 per 100 000 live births in the 2010 BMMS, yet halted in the 2016 BMMS at 46 per 100 000 live births. Although preeclampsia/eclampsia accounted for around one-fifth of all maternal deaths in the 2010 BMMS, in the 2016 BMMS, the percentage contribution reached the 2001 BMMS level of 24%. An analysis of the VA questionnaire's open section showed that almost all such death cases left their homes to seek care; however, most had to visit more than one facility before they died, indicating an unprepared health system.ConclusionsA cluster of preeclampsia/eclampsia-specific mortality observed during the first trimester, during delivery, and within 48 hours of birth indicates a need for preconception health check-ups and strengthened facility readiness. Awareness of maternal complications, proper care seeking, and healthy reproductive practices, like family planning to space and limit pregnancy through client-supportive counselling, may be beneficial. Improving regular and emergency maternal services readiness is also essential.

Project description:ImportanceOver the past 2 decades, there has been a trend toward increasing maternal age in many high-income countries. Maternal age may lead to greater attendant morbidity and mortality for Canadian mothers.ObjectiveTo investigate the association of maternal age, adjusting for patient-level and hospital-level factors, with severe maternal morbidity (SMM) and maternal death in Canada.Design, setting, and participantsA nationwide population-based cohort study of all antepartum, peripartum, and postpartum women and adolescents seen at Canadian acute care hospitals from April 1, 2004, to March 31, 2015. All analyses were completed on September 13, 2018.ExposuresMaternal age at the index delivery.Main outcomes and measuresSevere maternal morbidity and maternal death during pregnancy and within 6 weeks after termination of pregnancy.ResultsDuring the study period, there were 3?162?303 new pregnancies (mean [SD] maternal age, 29.5 [5.6] years) and 3?533?259 related hospital admissions. There were 54?219 episodes of SMM (17.7 cases per 1000 deliveries) in the entire study period, with a 9.8% relative increase from 2004-2005 to 2014-2015, in addition to an increasing proportion of pregnancies to older mothers. Independent patient-level factors associated with SMM included increasing Maternal Comorbidity Index; maternal age 19 years or younger and 30 years or older, with the greatest risk experienced by women 45 years or older (odds ratio [OR], 2.69; 95% CI, 2.34-3.06 compared with maternal age 20-24 years); and lowest income quintile (OR, 1.19; 95% CI, 1.14-1.22 compared with highest income quintile). Hospital-level factors associated with SMM included specific provinces. Independent patient-level factors associated with maternal mortality included increasing Maternal Comorbidity Index, age 40 to 44 years (OR, 3.39; 95% CI, 1.68-6.82 compared with age 20-24 years), age 45 years or older (OR, 4.39; 95% CI, 1.01-19.10 compared with age 20-24 years), and lowest income quintile (OR, 4.14; 95% CI, 2.03-8.50 compared with highest income quintile). Hospital-level factors associated with maternal mortality included lowest hospital pregnancy volume.Conclusions and relevanceIn Canada, maternal age and SMM have increased over the past decade. Results of this study suggest that province of residence, maternal comorbidity, residence income quintile, and extremes of maternal age, especially those 45 years or older, were associated with SMM and mortality. These findings are relevant to prospective parents, their health care team, and public health planning.

Dataset Information

The evolutionary dynamics of timing of maternal immunity: evaluating the role of age-specific mortality.

Publications

The evolutionary dynamics of timing of maternal immunity: evaluating the role of age-specific mortality.

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