Physiological changes in successive pregnancies and birth‐order effects

Abstract

An analysis of mortality rates documents that the well‐established female advantage in mortality continues to increase. Data from the U.S. census show that the sex differential in mortality has increased from 1.69 in 1963 to 1.82 in 1976. The age groups which show the most pronounced changes are youth (15–24), young adults (25–34), and old persons (75–84). Following Enterline (1961), we assess the major causes of death within each of these age groups in terms of their relative contributions to changing sex ratios. The major factors among young persons, apart from declining maternal mortality, are found to involve violent deaths, especially traffic accidents and suicide. Among old persons, death rates in general have declined, but advances in medical technology appear to have been more beneficial for older women than for older men, supporting the hypothesis of a biological superiority among women. However, death rates for malignant neoplasms have increased for older women as well as older men, suggesting that changing life styles may eventually have an impact on female mortality. The data suggest a need for additional research concerning the increase in violent deaths among young women and the potential increase in cancer deaths among older women.     

Coital rates,sex‐selective infanticide,and sex ratios at birth: A reply to James

Abstract

The cumulative onset curves for smoking, drinking, and sexual intercourse have been tracked through adolescence with reasonable success by recursive equations positing an “epidemic” or contagious process. The gist of these models is that the likelihood of onset in the next time period is proportional to the prevalence of the behavior among an adolescent's peers in the current time period. The present paper extends this approach to official delinquency. The fits to the data (from the Philadelphia cohort studies) are extremely tight. Several conceptual mismatches between the theory underlying the model and the model itself are discussed.     

Relationships between sex hormones assessed in amniotic fluid, and maternal and umbilical cord serum: what is the best source of information to investigate the effects of fetal hormonal exposure?

Levels of testosterone (T) (total and free), androstenedione (A4), dehydroepiandrosterone sulphate (DHEAS), sex hormone-binding globulin (SHBG), and estradiol (E2) were measured by radioimmunoassay (RIA) in 156 normal pregnancies (77 male and 79 female fetuses). Samples were obtained from amniotic fluid, 2nd and 3rd trimester maternal serum, and umbilical cord serum at birth. During the critical period of brain differentiation, at the beginning of the second trimester of pregnancy, sex differences in T and A4 were found in amniotic fluid and not in maternal serum. This finding adds to the fact that mostly low and nonsignificant correlations were found for the different androgenic hormones between levels assessed in amniotic fluid and maternal plasma at this particular and very sensitive period of fetal brain development. On the other hand, high correlations were found for the same hormones between the samples of maternal serum in the 2nd and the 3rd trimester. Our data show that, of all available sources, amniotic fluid seems to be the best candidate to investigate the effects of early fetal androgen exposure.     

Relation between age–sex classes and dietary selection of wild Japanese monkeys

Dietary selection by wild Japanese monkeys (Macaca fuscata yakui Kuroda) was examined in relation to body size. The monkeys were classified into three age–sex categories: adult males, adult females and immatures excluding suckling infants. Time spent feeding did not differ between age–sex classes, although time spent moving was longer in lighter classes. Heavier individuals fed relatively more on mature leaves, while lighter individuals fed on insects more frequently. Mature leaves were more abundant but had lower energy content than other food items in the forest. Heavier monkeys seemed to feed on greater amounts of lower quality food in this species. This finding agrees with the Jarman–Bell principle on ungulates.     

Cause‐specific mortality among older African‐Americans: Correlates and consequences of age misreporting

Abstract

This paper examines the quality of age reporting on death certificates of elderly African‐Americans by major causes of death. We utilize a sample of death certificates linked to early census records and to Social Security Administration records to establish a “true” age at death. We then examine the patterns, predictors, and consequences of age misreporting for major causes of death. We find a pattern of greater age misreporting among females, identify educational background as a key predictor of accurate age reporting, and show that mortality crossovers are eliminated for most causes of death when more accurate age data are used.     

The relation of sex,smoking status,birth rank,and parental age to β2-glycoprotein I levels and phenotypes in a sample of Australian Caucasian adults

Summary The serum level of ₂-glycoprotein I has been measured in a sample of 532 healthy, unrelated Caucasians resident in Melbourne. The distribution of levels is bimodal but lacks complete separation of the two modes. Samples with levels below 14.0 mg/100 ml are considered to be type I, and those above this level to be type N. The present sample contains 42 subjects of the former phenotype and 490 of the latter. The phenotypes are distributed equally between males and females and between smokers and nonsmokers and are unrelated to age, birth rank, or parental age. The gene frequencies for the Melbourne sample are compared with those found in various European samples.The ₂-glycoprotein I level of type N males is higher than that of females, and smokers have a higher level than nonsmokers. The positive regression of level on age is significant when corrections are made for sex and smoking status. ₂-glycoprotein I level is highly correlated with pseudocholinesterase activity.The pattern of inheritance of phenotypes has been examined in 17 families with a total of 56 children. In all families, this pattern is consistent with the currently accepted mode of autosomal codominant transmission.     

Are age and sex differences in brain oxytocin receptors related to maternal and infanticidal behavior in naïve mice?

This article is part of a Special Issue “Parental Care”.There is significant variability in the behavioral responses displayed by naïve young and adult mice when first exposed to pups. This variability has been associated with differences in the expression of oxytocin receptors (OXTRs) in the brain in several species. Experiment I investigated the behavioral responses of juvenile, adolescent, and adult CB57BL/6 males and females when first exposed to pups. We found an age increase in maternal females (11% of juveniles, 20% of adolescents, and 50% of young adults), and infanticidal males (0% of juveniles, 30% of adolescents, 44.5% of young adults, and 100% of older adults). Experiment II investigated OXTR density in the brain of juvenile and adult mice. Our results revealed an age decline in the density of OXTR in several brain regions, including the lateral septum, cingulated and posterior paraventricular thalamic nucleus in both males and females. Adult females had higher OXTR density in the ventromedial nucleus/postero-ventral hypothalamus (VMH) and the accessory olfactory bulb (AOB), but lower density in the ventral region of the lateral septum (LSv) than juveniles. Males had lower OXTR density in the anterior olfactory area (AOA) compared to juveniles. No age or sex differences were found in the medial preoptic area, and amygdaloid nuclei, among other brain regions. This study suggests that 1) maturation of parental and infanticidal behavioral responses is not reached until adulthood; 2) the pattern of development of OXTR in the mouse brain is unique, region specific, and differs from that observed in other rodents; 3) either up or down regulation of OXTR in a few brain regions (VMH/AOB/LSv/AOA) might contribute to age or sex differences in parental or infanticidal behavior.     

Kin and birth order effects on male child mortality: three East Asian populations, 1716–1945

Human child survival depends on adult investment, typically from parents. However, in spite of recent research advances on kin influence and birth order effects on human infant and child mortality, studies that directly examine the interaction of kin context and birth order on sibling differences in child mortality are still rare. Our study supplements this literature with new findings from large-scale individual-level panel data for three East Asian historical populations from northeast China (1789–1909), northeast Japan (1716–1870), and north Taiwan (1906–1945), where preference for sons and first-borns is common. We examine and compare male child mortality risks by presence/absence of co-resident parents, grandparents, and other kin, as well as their interaction effects with birth order. We apply discrete-time event-history analysis on over 172,000 observations of 69,125 boys aged 1–9 years old. We find that in all three populations, while the presence of parents is important for child survival, it is more beneficial to first/early-borns than to later-borns. Effects of other co-resident kin are however null or inconsistent between populations. Our findings underscore the importance of birth order in understanding how differential parental investment may produce child survival differentials between siblings.     

A survey on maternal age and karyotype in Down's syndrome in Japan, 1947–1975

Summary Data on karyotype and maternal age of 1954 cases of Down's syndrome were analyzed to see if the rate of chromosome mutations leading to this abnormality has been enhanced during the last 20 years. Comparison of the data for patients born in 1947–1960 with those in 1961–1975 revealed little change with time in the proportions of cases due to different karyotypes, the overwhelming majority being of 21 trisomy type in both periods. However, there has been a remarkable decline in the mean maternal age from 33.1 years to 29.7 years as well as in the variance from 50.5 to 29.4. While the rate of decline in the variance was almost the same as that for all births occurring in the same periods, the decline in the mean maternal age was much greater for the patients than for all births, suggesting that the rate of nondisjunction might have increased in younger rather than in older mothers. However, when the risk of brearing a child with Down's syndrome for mothers aged 40–44 is taken as unity, no evidence was found for an increase with time in the relative risk for younger mothers. Moreover, results of surveys made in 1960 and thereafter in different parts of Japan indicate that the crude incidence rate of Down's syndrome at birth has been around 0.10%, giving no indication of an upward trend. These findings are discussed with reference to the serious environmental pollution, including possible genetic hazards, with which Japan has been faced since the 1960s.     

Does education mediate the relationship between IQ and age of first birth? A behavioural genetic analysis

This study presents a multivariate behavioural genetic analysis of the relationship between education, intelligence and age of first birth. Analyses investigated the mediational role of education in explaining the relationship between intelligence and age of first birth at both the phenotypic and behavioural genetic level. The data come from the National Longitudinal Survey of Youth (NLSY), a nationally representative survey that included genetically informative full- and half-sibling pairs (n = 1423 pairs). Respondents were aged 14 to 22 when contacted in 1979. Heritability estimates were 0.32, 0.50 and 0.06 for IQ, education and age of first birth, respectively. Shared environment estimates were 0.35, 0.23 and 0.20 respectively. Common genetic and shared environmental factors were substantial in explaining the relationship between intelligence and education, and also education and age of first birth. Education partially mediated the relationship between intelligence and age of first birth only in the phenotypic analyses. After considering the genetic and shared environmental factors that influence all three variables, evidence for mediation was less convincing. This pattern of results suggests that the apparent mediational role of education at the phenotypic level is in fact the result of underlying genetic and shared environmental influences that affect education, IQ and age of first birth in common.     

Socioeconomic development,medical care,and nutrition as determinants of infant mortality in less‐developed countries

Abstract

Using data for sixty less‐developed countries, we constructed a causal model in which medical care, nutrition, status of women, and socioeconomic development are examined as determinants of infant mortality. Social and economic development are treated as exogenous variables; medical care, nutrition, and status of women are viewed as variables endogenous to the model. The model is tested by maximum likelihood methods. Results indicate that good nutrition and the presence of informally trained health care personnel, i.e., midwives, are more significantly related to low rates of infant mortality than are the employment status of women and the presence of formally trained health care personnel such as physicians and nurses. The general level of social and economic development conditions these relationships.     

Impact of maternal age on birth outcomes: a population-based study of primiparous Brazilian women in the city of São Paulo

The aim of this study is to analyse the impact of maternal age at first birth on low birth weight, preterm birth and low Apgar scores at one minute and at five minutes among live births delivered to primiparous Brazilian women in the city of S?o Paulo. Analyses were based on 73,820 birth records from the 1998 birth cohort. Logistic regression was used to assess the association between maternal age and each outcome variable, controlling for the following risk factors: delivery mode, plurality, sex, maternal education, number of prior losses, prenatal care, race, parity and community development. Maternal ages below 20 and above 30 years were significantly associated with the risks of low birth weight and preterm birth, but no association was found between maternal ages and Apgar score, with the exception that ages 15-19 reduced the odds of a low one-minute score. Even though this result seems to be inconsistent, low birth weight, preterm birth and low Apgar scores measure different dimensions of newborn well-being, and the association of each measure with maternal age is expected to diverge.     

Do group size and laying order influence maternal deposition of testosterone in smooth-billed ani eggs?

The avian egg contains maternal hormones that affect behavior, growth, morphology, and offspring survival. Evidence to date suggests that patterns of yolk androgen deposition could provide females with a means to manipulate sibling competition and, thereby, increase their fitness. We examined yolk testosterone (T) concentrations in eggs of the smooth-billed ani (Crotophaga ani) to understand patterns of androgen deposition in eggs of this plural-breeding joint-nesting cooperatively breeding species. We tested the hatching asynchrony adjustment hypothesis, which states that increases in yolk androgen levels over the laying sequence function to mitigate the disadvantage of being a later-hatched chick in species without adaptive brood reduction. We also investigated the effect of group size on yolk T deposition to test the hypothesis that females in multi-female groups could give a competitive edge to their own chicks by depositing higher T levels in their eggs. Predictions of the hatching asynchrony adjustment hypothesis were supported in both single- and multi-female groups as yolk testosterone levels increased from early- to late-laid eggs. This suggests that ani females can influence nestling competition and chick survival by within-clutch differential T allocation. Unexpectedly, we did not observe an effect of group size on yolk T deposition. Yolk testosterone concentrations may not be a mere reflection of a female's hormonal status as female plasma circulating levels of T did not vary in the same direction as yolk T levels. Results of this study therefore support the idea that females may adaptively manipulate chick behavior through hormonal deposition in eggs.     

Effect of maternal age and growth on placental nutrient transport: potential mechanisms for teenagers' predisposition to small-for-gestational-age birth?

Teenagers have an increased risk of delivering small-for-gestational-age (SGA) infants. Young maternal age and continued skeletal growth have been implicated as causal factors. In growing adolescent sheep, impaired placental development and nutrient transfer cause reduced birth weight. In human pregnancies, SGA is associated with reduced placental amino acid transport. Maternal growth has no effect on placental morphology or cell turnover, but growing teenagers have higher birth weight:placental weight ratios than nongrowing teenagers. We hypothesized that placental nutrient transporter activity would be affected by maternal age and/or growth status. Placentas from teenagers and adults were collected. Teenagers were defined as growing or nongrowing based on knee height measurements. System A amino acid transporter activity was quantified as sodium-dependent uptake of [(14)C]methylaminoisobutyric acid into placental fragments. Teenagers had lower placental system A activity than adults (P < 0.05). In adults, placental system A activity was lower in SGA infants than appropriate-for-gestational-age (AGA) infants (P < 0.05). In teenagers, AGA and SGA infants had lower placental system A activity than AGA infants born to adults (P < 0.05). Placental system A activity was higher in growing teenagers than in nongrowing teenagers (P < 0.001). Placental mRNA expression of system A transporter isoforms SLC38A1 and -2 was lower in teenagers than in adults (P < 0.05) but did not differ between growing and nongrowing teenagers. There was no difference in transporter protein expression/localization between cohorts. Teenagers have inherently reduced placental transport, which may underlie their susceptibility to delivering SGA infants. Growing teenagers appear to overcome this susceptibility by stimulating the activity, but not expression, of system A transporters.     

Childhood conditions,migration, and mortality: Migrants and natives in 19th‐century cities

Abstract

Migrants often have lower mortality than natives in spite of relatively unfavorable social and economic characteristics. Although migrants have a short‐run advantage due to the selective migration of healthy workers, persistent health and mortality differences between migrants and natives may be long‐run effects of different experiences in childhood. We made use of a natural experiment resulting from rural‐to‐urban migration in the mid‐19th century. Mortality was much higher in urban areas, especially in rapidly growing industrial cities. Migrants usually came from healthier rural origins as young adults. Data used in this study is available from 19th‐century Belgian population registers describing two sites: a rapidly growing industrial city and a small town that became an industrial suburb. We found evidence of three processes that lead to differences between the mortality of migrants and natives. First, recent migrants had lower mortality than natives, because they were self‐selected for good health when they arrived. This advantage decreased with time spent in the destination. Second, migrants from rural backgrounds had a disadvantage in epidemic years, because they had less experience with these diseases. Third, migrants from rural areas had lower mortality at older (but not younger) ages, even if they had migrated more than 10 years earlier. We interpret this as a long‐run consequence of less exposure to disease in childhood.     

Relationships between Religion and Two Forms of Homonegativity in Europe—A Multilevel Analysis of Effects of Believing,Belonging and Religious Practice

This paper examines relationships between religion and two forms of homonegativity across 43 European countries using a bivariate response binary logistic multilevel model. The model analyzes effects of religious believing, belonging and practice on two response variables: a) a moral rejection of homosexuality as a practice and b) intolerance toward homosexuals as a group. The findings indicate that both forms of homonegativity are prevalent in Europe. Traditional doctrinal religious believing (belief in a personal God) is positively related to a moral rejection of homosexuality but to a much lesser extent associated with intolerance toward homosexuals as a group. Members of religious denominations are more likely than non-members to reject homosexuality as morally wrong and to reject homosexuals as neighbors. The analysis found significant differences between denominations that are likely context-dependent. Attendance at religious services is positively related to homonegativity in a majority of countries. The findings vary considerably across countries: Religion is more strongly related to homonegativity in Western than in Eastern Europe. In the post-soviet countries homonegativity appears to be largely a secular phenomenon. National contexts of high religiosity, high perceived government corruption, high income inequality and shortcomings in the implementation of gay rights in the countries’ legislations are statistically related to higher levels of both moralistic homonegativity and intolerance toward homosexuals as a group.     

Prostaglandin 15-hydroxy dehydrogenase and Δ13 reductase levels in the lungs of maternal,fetal and neonatal rabbits

The levels of prostaglandin 15-hydroxy dehydrogenase and reductase have been studied in the lungs of maternal, fetal and neonatal rabbits. Fetal lungs obtained at gestational age of 28–30 days (full term 31 days) had the same levels of prostaglandin dehydrogenase as the adults, while the reductase levels in the fetal lungs were only one fourth that in the adults. The lungs of maternal rabbits at near term possessed very high levels of prostaglandin dehydrogenase — approximately twenty-fold higher than in the adult non-pregnant female controls. The Δ¹³ reductase appeared slightly elevated during pregnancy. Neonatal animals at different ages showed the same levels of both enzymes as the near term fetus and/or the non-pregnant adults, which suggests that the development of the ability for prostaglandin metabolism is completed at least several days before birth. The high dehydrogenase levels in the near term maternal lungs indicated the requirement for extra protection against prostaglandin release during late pregnancy.     

A gene‐based evolutionary explanation for the association between criminal involvement and number of sex partners

Abstract

Empirical research has revealed a positive relationship between number of sex partners and involvement in antisocial behaviors. Most attempts to explain this association have taken an evolutionary perspective and argued that the same traits (e.g., impulsiveness, shortsightedness, and aggressiveness) that are related to a large number of sex partners are also related to criminal involvement However, there is also reason to believe that the covariation between sex partners and crime behaviors can be partially explained by a common genetic pathway, where genes that are related to sex partners are also related to antisocial conduct. We test this possibility by using data from the National Longitudinal Study of Adolescent Health (Add Health). Specifically, we examine whether variants of the dopamine transporter gene (DAT1) are associated with number of sexual partners and with adult criminal behavior. The results of our analyses reveal two broad findings. First, and in line with prior research, we find that there is a strong positive association between sex partners and antisocial behavior. Second, DAT1 explains variation in both number of sexual partners and in criminal conduct for males. We speak to the implications of our findings.