Pregnancy outcome for nomadic Turkana pastoralists of Kenya

The outcome of an individual pregnancy is a key component of overall reproductive success and is strongly influenced by environmental, behavioral, and biological variation within populations. This prospective study examined the outcomes of 68 pregnancies among nomadic Turkana of Kenya from July 1993 to July 1994. A total of 12 women experienced pregnancy losses, and 3 women experienced live births with a subsequent perinatal death. The following characteristics are associated with increased risk for experiencing a fetal or perinatal death: severe morbidity episodes, shorter nonpregnant intervals, lower third-trimester weight, higher third-trimester summed skinfolds but limited third-trimester reduction in summed skinfolds, and higher activity levels late in gestation. Turkana newborns measured within 48 hr of birth (n = 19) weighed an average of 2,860 +/- 640 g and had a mean ponderal index of 2.72 +/- 0.46. Variation in birth weight was predicted by preterm delivery, delivery during the wet season, and maternal morbidity levels. Birth length averaged 50.8 +/- 6.8 cm and was positively influenced by full term delivery, better maternal health, and birth during the dry season. These results suggest complicated pathways linking the physical environment, subsistence requirements, heterogeneity in maternal fitness, behavior, and pregnancy outcome. The results augment the larger picture of reproductive success for Turkana nomads who live in a highly variable savanna environment.     

Premarital childbearing in northwest Kenya: challenging the concept of illegitimacy

A number of African countries, including Kenya, have experienced a marked rise in births among unmarried women. In Western countries, reproduction outside of marriage is assumed to be illegitimate and a social problem. One hypothesis used to explain the increasing incidence of premarital fertility in Africa is a breakdown of traditional social controls by the extended family over the sexual behavior of adolescents. A competing hypothesis suggests that unmarried women use sexual relations to achieve goals such as marriage. Among Turkana pastoralists of northwest Kenya, we find a pattern of premarital birth that fits either hypothesis only loosely. Premarital fertility among the Turkana is both widespread and culturally acceptable, with over 30 per cent of women having at least one child prior to marriage. Although women with premarital births initiate childbearing on average one year earlier than women with only marital births, women's marital status does not influence the length of the interval between first and second births. Marriage among the Turkana is not a social trigger for the onset and continuation of reproduction or a means to legitimate reproduction. Marital status of the parents simply determines the custody of a child. In a premarital birth, the father pays a set fee to the mother's family, and the custody of the child remains permanently with the mother's family. If the parents later marry, the father must purchase custody of the child by another fee at that time. Since the Turkana have experienced few effects of modernization, the existence of such a practice suggests that cultural factors must be taken into account before assessing premarital fertility in Africa as a social problem.     

Maternal influences on offspring phenotypes and sex ratios in a multi‐clutching lizard with environmental sex determination

Maternal and environmental factors are important sources of phenotypic variation because both factors influence offspring traits in ways that impact offspring and maternal fitness. The present study explored the effects of maternal factors (maternal body size, egg size, yolk‐steroid allocation, and oviposition‐site choice) and seasonally‐variable environmental factors on offspring phenotypes and sex ratios in a multi‐clutching lizard with environmental sex determination (Amphibolurus muricatus). Maternal identity had strong effects on offspring morphology, but the nature of maternal effects differed among successive clutches produced by females throughout the reproductive season (i.e. maternal identity by environment interactions). The among‐female and among‐clutch variation in offspring traits (including sex ratios) was not mediated through maternal body size, egg size, or variation in yolk steroid hormones. This lack of nongenetic maternal effects suggests that phenotypic variation may be generated by gene by environment interactions. These results demonstrate a significant genetic component to variation in offspring phenotypes, including sex ratios, even in species with environmental sex determination. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 256–266.     

Modeling breastmilk infectivity in HIV-1 infected mothers

Estimation of breastmilk infectivity in HIV-1 infected mothers is difficult because transmission can occur while the fetus is in utero, during delivery, or through breastfeeding. Since transmission can only be detected through periodic testing, however, it may be impossible to determine the actual mode of transmission in any individual child. In this article we develop a model to estimate breastmilk infectivity, along with the probabilities of in-utero and intrapartum transmission. In addition, the model allows separate estimation of early and late breastmilk infectivity, and individual variation in maternal infectivity. Methods for hypothesis testing of binary risk factors and a method for assessing goodness of fit are also described. Data from a randomized trial of breastfeeding versus formula feeding among HIV-1 infected mothers in Nairobi, Kenya, are used to illustrate the methods.     

Juvenile perpetrators of homicides and attempted homicides--a case control study

The aim of this study was to explore the influence of certain aspects of family dynamics, as well as some behavior and psychological development disorders on the occurrence of homicides and attempted homicides among juveniles in the Split Dalmatian County over a period of 10 years (1989-1998). A retrospective case-control study was performed to compare juvenile murderers and attempted murderers with minors who committed other offences, i.e. property crimes. The subjects were paired according to demographic and socio-economic background. The data obtained from County Court's files included social anamnesis, specialists' observation and psychiatric expertise results. There was a significant difference between the study group and their controls in the frequency of physical violence and parental rejection during childhood. Neuropsychological and neurophysiological abnormalities were more frequent in the experimental than in the control group. Stealing occurred more often in the control group. No significant differences were found for other studied risk factors. There is no unique type of juvenile murderer. A juvenile homicide is committed under the influence of various developmental characteristics, family milieu, and constitution combined with environmental factors and perpetrator's perception of the victim.     

Influence of environmental and physical factors on capture of Tribolium castaneum (Coleoptera: Tenebrionidae) in a flour mill

Variation in environmental and physical factors within food processing facilities can influence both the distribution of stored-product pests and trapping efficiency. Data from a long-term Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) monitoring program was used to evaluate spatial variation in captures among trap locations and to determine relationships with environmental and physical variables. From the complete monitoring data set, different subsets were created for the cool and warm seasons, and period of time when environmental and physical factors were measured (2009-2010), with all data sets showing significant differences among trap locations in terms of beetle captures and proportion of time that traps exceeded 2.5 beetles per trap per monitoring period. There was also considerable temporal variation in distribution among the different levels of the mill. Among the environmental and physical variables measured, mean temperature and flour dust accumulation showed the most significant positive relationships with variation of beetle captures at trap locations. More beetles were captured in traps located in close proximity to milling equipment. Presence of equipment near traps was also associated with an increase in flour dust accumulation and temperature. Overall the environmental and physical factors seemed to have a limited influence on variation in captures among trap locations, with temporal variation in distribution perhaps overwhelming potential influences of local trap conditions.     

An investigation into proximate determinants responsible for fertility differentials between two rural Bangladeshi populations

The substantial areal variation in Bangladesh's demographic dynamics is demonstrated by the differential fertility in 2 rural areas--Teknaf, where the total fertility rate is 8.0 and Matlab, where this rate is 6.5 in comparison areas and 5.0 in treatment areas. The fertility differences between the comparison and treatment areas of Matlab are usually attributed to the differential use of contraception, while the fertility difference between Teknaf and Matlab as a whole is assumed to reflect dissimilarities in socioeconomic, environmental, and cultural conditions. Application of a model proposed by Bongaarts which permits analysis of the effects of intermediate variables on fertility reveals similar marital patterns in Teknaf and Matlab but different indexes of infecundability and contraceptive use. Both the comparison and treatment areas of Matlab had 1 birth less than Teknaf because of their high infecundability due to a longer duration of breastfeeding (median duration of 30 months in Matlab compared with 22 months for Teknaf). Contraceptive use contributed 0.51 and 2.36 fewer births in Matlab's comparison and treatment areas, respectively, than in Teknaf. The reasons Teknaf mothers breastfeed their infants for shorter durations than Matlab mothers merit further investigation given the significant contribution of prolonged lactational amenorrhea to lowering fertility. Much of the effect on fertility of the increase in contraceptive use in Matlab's experimental area could not have been achieved if lactation durations were at Teknaf levels, further emphasizing the need for research on breastfeeding behavior in different parts of Bangladesh.     

Exploring the genetic basis and proximate causes of female fertility advantage in gynodioecious Thymus vulgaris

In many gynodioecous species, females produce more viable seeds than hermaphrodites. Knowledge of the relative contribution of inbreeding depression in hermaphrodites and maternal sex effects to the female fertility advantage and the genetic basis of variation in female fertility advantage is central to our understanding of the evolution of gender specialization. In this study we examine the relative contribution of inbreeding and maternal sex to the female fertility advantage in gynodioecious Thymus vulgaris and quantify whether there is genetically based variation in female fertility advantage for plants from four populations. Following controlled self and outcross (sib, within-population, and between-population) pollination, females had a more than twofold fertility advantage (based on the number of germinating seeds per fruit), regardless of the population of origin and the type of pollination. Inbreeding depression on viable seed production by hermaphrodites occurred in two populations, where inbreeding had been previously detected. Biparental inbreeding depression on viable seed production occurred in three of four populations for females, but in only one population for hermaphrodites. Whereas the maternal sex effect may consistently enhance female fertility advantage, inbreeding effects may be limited to particular population contexts where inbreeding may occur. A significant family x maternal sex interaction effect on viable seed production was observed, illustrating that the extent of female fertility advantage varies significantly among families. This result is due to greater variation in hermaphrodite (relative to female) seed fertility between families. Despite this genetic variation in female fertility advantage and the highly female biased sex ratios in populations of T. vulgaris, gynodioecy is a stable polymorphism, suggesting that strong genetic and/or ecological constraints influence the stability of this polymorphism.     

A Comparison of Health Complaints of Settled and Nomadic Turkana Men

This article examines the health complaints of settled and nomadic Ngisonyoka Turkana of northwest Kenya. Samples of 152 nomadic and 124 settled men, aged 14 and over, were surveyed about their health status. The general pattern of disease reported concurs with previous studies of health among Turkana; that is, the primary complaints are respiratory tract infections and eye infections. The settled Turkana reported more severe complaints and higher rates of infectious disease than the nomads, including a significantly higher frequency of cold with cough, eye infection, and chest infection. Although the settled males as a group had slightly higher body mass index and other measures of body fat than the nomadic group, none of these indicators of body composition were predictive of health complaints. Observed differences in health patterns are possibly related to differences in dietary composition, exposure to pathogens associated with population density and environmental pollution, physical activity patterns, and psychosocial stress.     

Extreme seasonality of births among nomadic Turkana pastoralists

Births to nomadic Turkana women in northwest Kenya follow one of the most highly seasonal distributions ever reported for a human population, with more than half of all births falling between March and June. Important aspects of the Turkana environment also fluctuate greatly over the course of the year. The rate of conception is apparently highest during the early dry season, when the food supply has been at its best for some time, and when women are attaining their peak nutritional status. The seasonal dynamics of Turkana fertility seem to be driven, ultimately, by fluctuations in rainfall; Fourier analysis indicates that changes in numbers of conceptions follow changes in rainfall with a lag of 3.6 months. The specific biological and behavioral changes in the human population through which the environmental changes may affect fertility are considered.     

Physiological mechanisms,behavioral and psychological factors influencing the transfer of milk from mothers to their young

This article is part of a Special Issue “Parental Care”.Producing milk to support the growth of their young is a central element of maternal care in mammals. In spite of the facts that ecological constraints influence nursing frequency, length of time until weaning and the composition of milk, there is considerable similarity in the anatomy and physiology of milk production and delivery across mammalian species. Here we provide an overview of cross species variation in nursing patterns and milk composition as well as the mechanisms underlying mammary gland development, milk production and letdown. Not all women breastfeed their infants, thus in later sections we review studies of factors that facilitate or impede the initiation and duration of breastfeeding. The results of these investigations suggest that the decisions to initiate and maintain breastfeeding are influenced by an array of personal, social and biological factors. Finally, studies comparing the development of breastfed and formula fed infants as well as those investigating associations between breastfeeding, maternal health and mother/infant interaction are reviewed. Leading health agencies including the World Health Organization and CDC advocate breastfeeding for at least the first 6 months postpartum. To achieve these rates will require not only institutional support but also a focus on individual mother/infant dyads and their experience.     

The influence of maternal care in shaping human survival and fertility

The influence of maternal care on child survival has evolved throughout human history due to variation in altriciality, allocare, and maternal behaviors. Here, we study the impact of these factors on the force of selection acting on age-specific survival and fertility (measured with elasticity analysis) in a model that incorporates the dependence of child survival on maternal survival. Results reveal life-history changes that cannot be elucidated when considering child's survival independent of maternal survival: decrease of late fertility and increase of late survival, and concomitant decrease of early and late fertility. We also show that an increase of child altriciality in early humans might explain the main human life-history traits: a high life expectancy and postreproductive life; a long juvenile period and a higher, and narrowed, fertility at the peak of the reproductive period.     

Human fertility studies under field conditions. Introduction.

Human fertility is part of biological anthropology embracing human population biology devoted to the analysis of the nature, caused, origin, and development of human variation at molecular, cellular, and whole body levels. The successful outcome of human fertility depends on the interactions of biochemical, physiological, and psychological processes whose disturbance results in slight variations in behavior and even total infertility. The Hutterites in the US have the highest average fertility with over 11 live births/women. Hunter-gatherer groups rarely have more than 4 children/woman. The case of a woman who gave birth to 67 children was recorded. Total infertility often occurs even in noncontracepting societies. The most important factor that determines the character of genetic variation within the human species seems to be comparative population growth, as this was the factor determining which populations spread and which became extinct. The study of the determinants of female fertility has attracted attention recently because pregnancy and motherhood affect daily life, and in turn, reproduction is also affected by daily life. Lactational amenorrhea plays a vital role in child spacing, but the mechanism of breast feeding is complex with factors of duration, frequency, milk production, and suckling frequency interwoven. Female reproduction comprises whole body function, nutrition, body composition (the recent debate on fat stores affecting the onset of fertility), physical work, and mental health all influencing the endocrinological state. Heavy physical labor and intensive training by sportswomen can result in amenorrhea. Beta-endorphins also play a role in lactational amenorrhea along with nutrition and body composition. Infectious and venereal diseases particularly affect fertility, yet genetics protect the placenta against falciparum malaria in sickle-cell trait women.     

浙江清凉峰自然保护区土壤肥力指标空间变异及其影响因素

为了探究清凉峰自然保护区内华南野生梅花鹿主要栖息地千顷塘的土壤肥力指标的空间变异规律及其相关影响因子,采用经典统计学和地统计学方法对千顷塘土壤pH、有机质、全磷、全氮、全钾含量进行了系统分析,并探讨了其主要影响因子。结果显示：千顷塘保护区内土壤整体呈酸性,区域内有机质、全磷、全氮、全钾含量均值分别为72.44、0.45、1.91、23.16 g/kg,所有指标均呈现中等程度变异。半方差分析结果表明,指数模型为pH、全磷、全氮、全钾的最佳拟合模型,球状模型为有机质最佳拟合模型,pH、全磷、全钾空间自相关强烈,显示其空间变异主要受结构性因素影响,有机质和全氮空间自相关程度中等,说明随机因素存在一定影响。全局Moran′s I指数检验结果显示,有机质、全磷和全氮存在显著空间自相关,在空间上呈现聚集分布。所有肥力指标的空间分布较为连贯,条带状分布特征显著,总体呈现由边缘向中间降低趋势;相关性分析显示,土壤有机质、全磷、全氮、全钾与海拔、容重和植被类型呈显著相关性;回归分析表明,在所有环境因子中,容重对各类元素的方差解释最大,是影响千顷塘土壤肥力因子空间异质性的主控因素。研究可为南方丘陵地区人为...     

Selenium intake and status of postpartum women and postnatal depression during the first year after childbirth in New Zealand – Mother and Infant Nutrition Investigation (MINI) study

BackgroundSelenium (Se) plays an important role in selenoproteins as an antioxidant, and is involved in thyroid function, mental health and child development. Selenium is low in the local food supplies in NZ. Low selenium intake has been reported in women of childbearing age and postmenopausal women, however, there is little research relating to breastfeeding women and their infants.PurposeThe study investigates maternal and infant selenium intake and status during the first year postpartum, and possible relationships to postnatal depression and anxiety.Basic proceduresThe Mother and Infant Nutrition Investigation (MINI) study is an observational longitudinal cohort study. In total 87 breastfeeding mother-infant pairs were recruited and followed up at 3, 6 and 12 months postpartum. Maternal selenium intake was estimated from a four-day diet diary (4DDD). Selenium concentrations were measured in maternal spot urine, breastmilk and plasma; and infant spot urine samples. Postnatal depression was screened by the Edinburgh Postnatal Depression Scale (EPDS) questionnaire.Main findingsMedian maternal selenium intake was 62 (50, 84) μg/day, with 56 % below the Estimated Average Requirement (EAR) of 65 μg/day. At 3, 6, and 12 months postpartum, median maternal urinary selenium:creatinine ratios were 29.0 (22.4, 42.0), 29.5 (23.1, 28.4), and 30.9 (24.3, 35.3) μg/g; median infant urinary selenium concentrations (IUSC) were 8 (6,13), 11 (6, 15), and 24 (10, 40) μg/L; median breastmilk selenium concentrations (BMSC) were 13 (11, 14), 11 (9, 11) and 12 (11, 13) μg/L; 18 %, 11 % and 14 % of women reported probable minor depression based on the EPDS scores equal or above 10. Estimated median infant selenium intake at 3 and 6 months were 9 (8, 11) and 8 (7, 10) μg/day with 85 % and 93 % below the Adequate Intake of 12 μg/day. Median maternal plasma selenium was 105.8 μg/L at 6 months postpartum. Minor depression at three months postpartum was significantly different across tertiles of plasma selenium concentrations (p = 0.041).Principle conclusionsSuboptimal selenium intake was observed among breastfeeding mothers and their infants in the MINI study. Potentially, some women had insufficient selenium status. Relation between selenium status and risk of postnatal depression and anxiety was inconclusive.Further research is required to explore effects on maternal thyroid function and infant neurodevelopment among women with inadequate selenium intake and status.     

Breast-feeding pattern in an urban Nigerian community

This paper examines the pattern of breastfeeding among women still in their prime childbearing ages (15-35 years) in Ilorin, the capital city of Kwara state in Nigeria. While breastfeeding is still a common practice among urban women, there is wide variation in the duration of breastfeeding depending on the socioeconomic characteristics of the mothers. Mother's education and father's education have very strong negative associations with duration of breastfeeding. Use of contraception also has a significant independent but negative effect on breastfeeding duration. Christians continue breastfeeding for shorter periods than Muslims. The introduction of supplementary feedings to the infant occurs in this population much earlier than is recommended by various authorities. Decline in breastfeeding practice may have deleterious effects on the health and survival of children in developing countries and may also lead to higher fertility and more rapid population growth. The high morbidity and mortality among artificially fed infants in many developing countries can be attributed to improper preparation as well as contamination of infant formula and other foods.     

Kin influences on fertility in Thailand: Effects and mechanisms

It has been suggested that human mothers are cooperative breeders, as they need help from others to successfully raise offspring. Studies working under this framework have found correlations between the presence of kin and both child survival and female fertility rates. This study seeks to understand the proximate mechanisms by which kin influence fertility using data from the 1987 Thailand Demographic and Health Survey (DHS), a nationally representative sample of 6775 women. Kin influence is measured by the length of time couples live with the husband's or wife's parents after marriage. Event history analysis, multilevel modeling and structural equation modeling are used to investigate both fertility outcomes and potential pathways through which postnuptial residence may influence fertility outcomes, including employment status, maternal and child outcomes, contraceptive use, breastfeeding duration, and age at marriage. We show that living virilocally (with husband's kin after marriage) increases total fertility by shortening time from marriage to first birth, and increasing the likelihood of progression to each subsequent birth. These effects are mediated through correlations between virilocal residence and earlier age at marriage as well as delayed initiation of contraceptive use. We find no influence of husband's kin on maternal or child outcomes. Living uxorilocally (with wife's kin after marriage) also reduces age at marriage, shortens time from marriage to first birth and (marginally) improves child survivorship, but has no effect on other child and maternal outcomes or progression to subsequent births and results in a similar number of living children as women living neolocally.     

Analysis of woody vegetation of Corbett National Park,India

The heterogeneous vegetation mosaic of the South Turkana region of north Kenya is associated with diversity in the region's physical environment. The abundance and distribution of the dominant species are related to gradients in those abiotic factors that influence water availability, including precipitation, soil texture, and topographic relief. Research focused on three Acacia species that are a major component of the Turkana vegetation; A. tortilis, A. senegal, and A. reficiens. These species each exhibit a different response to variations in abiotic factors. Consequently, species abundance varies independently across the landscape, creating a continuum of intergrading populations. Community types can be identified within the mosaic of intergrading populations. Although community borders are not discrete due to continual change in species abundance, types are identifiable and are repeated in areas with similar environmental conditions. The landscape patterns are representative of Whittaker's (1953) climaxas-pattern, with communities created by individual patterns of populations responding to environmental gradients, creating a continuum of community change across the landscape.     

Demographic and health status risk factors in childbearing among Indian women. Evidence from hospital data for the later stages of fertility decline

Indirect estimates of maternal mortality in India indicate that fertility decline has reduced maternal deaths by reducing the frequency of pregnancy and childbirth. The earlier stages of fertility decline are also likely to have lowered maternal mortality by reducing the risk of pregnancy and childbirth as the proportion of births among risky multiparous, older women declines. However, further fertility decline may well be associated with some increase in risk. Risk will also remain high if the health status of Indian girls and women remains poor. This study uses a sample of maternal deaths and deliveries among patients who survived which occurred in Civil Hospital, Ahmedabad, Gujarat during 1982-1993 to investigate these issues further. The women in the sample have relatively low fertility and represent a fairly late stage of fertility decline. They also have persistently poor health status. Logit regression analysis reveals that although fertility decline is associated with some increase in risk, poor health status is the more important maternal mortality risk factor. Without attention to female health, even childbearing among expectant mothers with low fertility continues to be hazardous.     

A causal analysis of birth weight in the offspring of monozygotic twins.

Data were collected on the birth weights of 1,694 offspring of 385 sets of twins including 108 male and 131 female monozygotic pairs. To resolve the influence of birth order from the genetic, environmental, and maternal effects on birth weight, we analyzed the full-sib and maternal and paternal half-sib correlation matrices for birth orders one to five using a causal model that assumed each live-born child had an influence on the weight of the subsequent birth. Prenatal maternal influences explained 40% of the variation in birth weight of the first-born child and 52% for the fifth child; genetic or environmental factors common to monozygotic twins accounted for 72% of this effect, while environmental variables unique to individual mothers were responsible for the remaining 28%. The inclusion of a birth-order parameter resulted in a highly significant improvement in the goodness of fit of the causal model such that by the fifth child, 46% of the maternal variation could be attributed to the cumulative effects of previous live births.