Doctoral Dissertation Improvement: Maternal reproductive trade-offs and the duration of exclusive breastfeeding in a natural fertility population

国际卫生组织建议在婴儿出生后的头6个月纯母乳喂养，以促进婴儿最佳生长并减少感染传染病的风险。然而，在全球范围内，6个月的纯母乳喂养相对罕见——包括在许多传染病高发的欠发达人口中。对许多母亲来说，6个月前补充喂养的风险可能并不明显，或者可能被时间和精力需求的竞争所抵消。本研究将调查玻利维亚经济边缘化人口提斯曼人的婴儿喂养模式和相关结果的差异。加州大学圣巴巴拉分校（University of California, Santa Barbara）的博士生Melanie Martin在Michael Gurven博士的指导下进行的这项研究，验证了产妇工作和照顾孩子的需求会缩短纯母乳喂养时间的假设。此外，由于哺乳期母亲体重会迅速减轻，而且不会来月经，Tsimane母亲可能会在6个月大之前引入辅食，以尽量减少哺乳期的热量损失。这种抵消可以使产后体重维持和月经的早期恢复。提斯曼妇女无法获得避孕药具；因此，早期补充喂养可能有助于提斯曼母亲的高生育率（平均9个孩子）。研究人员将对提斯曼族的母亲进行调查，以确定纯母乳喂养的时间长短是否会随着婴儿的状况、母亲的年龄和身体状况、以及母亲的工作和育儿需求而变化。研究人员还将前瞻性地收集提斯曼族母亲和婴儿的饮食、行为和生物学数据，以研究补充喂养模式如何影响母亲的能量、月经状况、婴儿生长和发病率。该研究将考察当地信仰和提斯曼母亲对婴儿健康、生长和发育的看法如何进一步影响喂养决定。研究结果将有助于制定战略，促进在文化上可接受的婴儿喂养做法，以最佳方式有益于母婴健康。

International health organizations recommend exclusive breastfeeding for the first 6 months of life to promote optimal infant growth and reduce risk of infectious illness. Globally, however, exclusive breastfeeding for 6 months is relatively rare - including in many less developed populations with high rates of infectious disease. For many mothers, the risks associated with complementary feeding before 6 months of age may not be apparent, or may be outweighed by competing time and energy demands. This study will examine differences in infant feeding patterns and associated outcomes in an economically marginalized population, the Tsimane of Bolivia.This research by doctoral student Melanie Martin (University of California, Santa Barbara), under the supervision of Dr. Michael Gurven, tests the hypothesis that maternal work and childcare demands reduce the length of exclusive breastfeeding. Furthermore, because nursing mothers rapidly lose weight and do not menstruate, Tsimane mothers may introduce complementary foods before 6 months of age to minimize the caloric losses of nursing. This offset may enable postpartum weight maintenance and earlier resumption of menstruation. Tsimane women do not have access to contraceptives; early complementary feeding may therefore contribute to Tsimane mothers' high fertility rates (average 9 children). The researchers will survey Tsimane mothers to determine if the length of exclusive breastfeeding varies with infant condition, maternal age and condition, and maternal work and childcare demands. Researchers will also prospectively collect dietary, behavioral and biological data from Tsimane mothers and infants to examine how complementary feeding patterns affect maternal energy, menstrual status, infant growth and incidence of illness. The study will examine how local beliefs and Tsimane mothers' perceptions of infant health, growth, and development further influence feeding decisions. Results will aid in devising strategies to promote culturally acceptable infant feeding practices that optimally benefit maternal and infant health.