Stable aggregate fertility in a time of family change: a decomposition of trends in American fertility, 1970-1999

Population-level birth rates in the United States were largely stable between 1970 and 1999. This stability contrasts with rapid change in marriage rates and fertility timing during the same period. In this article, I use decomposition techniques to analyze this seeming paradox. I decompose the general fertility rate into four components: age distribution, marital status, age-specific nonmarital fertility, and age-specific marital fertility. Absent other changes, declining time spent married would have led to substantial decline in fertility. Several factors combined to counterbalance these changes in marital behavior. Among white women in the 1970s and 1980s, marital fertility rates increased at older ages, consistent with a scenario in which women postponed both marriage and childbearing; increased nonmarital birth rates during this period were not a driving factor in overall fertility trends. Increased nonmarital fertility was more important in compensating for declining time spent married among African American women and among white women in the 1990s.     

American Indians with African Ancestry: Differential Fertility and the Complexities of Social Identity

Interethnic marriage represents a major trend in the demographic history of American Indians. While the majority of these unions involved Indian women and Caucasian men, a sizeable number occurred between Indians and African Americans. The children of these bicultural marriages were “mixed bloods” who in turn typically married non-Indians or other mixed bloods. Using data from the 1910 Census on American Indians in the United States and Alaska, this article explores why American Indians with African ancestry enjoyed high fertility. Differential rates of fertility among American Indians in the past were due to a number of underlying genetic, cultural, and environmental factors. By identifying these factors, the paradox of why Indian women with African heritage did so well in terms of fertility largely disappears. African admixture, however, greatly complicates Indian social identity.     

Women’s strategies in polygynous marriage

Both behavioral ecological and social anthropological analyses of polygynous marriage tend to emphasize the importance of competition among men in acquisition of mates, whereas the strategic options to women both prior to and after the establishment of a marriage have been neglected. Focusing on African marriage systems that are in some senses analogous to resource-defense polygyny, I first review the evidence of reproductive costs of polygyny to women. Then I discuss why the conflict of interests between men and women over mate number is often likely to be settled in favor of men. Using East African ethnographic data I examine the strategic responses of women and their families to polygynous marriage, focusing on four topics: mate choice (Kipsigis), attitudes toward incoming wives (Kipsigis), labor allocation and cooperation (comparative data, Kipsigis), and use of parental wealth (Datoga). The results of these quantitative analyses suggest that through a combination of judicious marriage choice and strategic responses within marriage, polygyny need not be costly to women in resource-defense polygynous systems. The conclusion is that a hierarchy of questions need to be addressed in the analysis of any polygynous marriage system.     

Resemblance for Body Mass Index in Families of Obese African American and European American Women

Objective: We determined the levels of resemblance in body mass index (BMI) in large samples of families selected through obese African American and European American women. Research Methods and Procedures: We examined correlations among relatives in 1185 European American and African American families ascertained through age-matched obese women (BMI ≥ 30 kg/m²). A subset of 801 families were ascertained through extremely obese women (BMI ≥ 40 kg/m²). Results: Parent-offspring and sibling correlations ranged from 0.19 to 0.15, suggesting a moderate level of heritability in both groups. Mean BMI values for female relatives were lower for European Americans than for African Americans even though probands were matched, perhaps because the European American relatives regress to a lower population mean. We found significantly higher family correlations for height in European Americans, suggesting greater environmental variability among African Americans for factors affecting growth and physical development. Discussion: Our results suggest a similar level of heritability of BMI in families of obese African American and European American women. Other genetic studies will be needed to determine the extent to which the same or different genes and environmental conditions contribute to an overall similar heritability in the two racial groups.     

Weight loss goals among African-American women with type 2 diabetes in a behavioral weight control program

African‐American women with type 2 diabetes experience limited weight loss in behavioral weight control programs. Some research suggests that overly ambitious weight loss expectations may negatively affect weight losses achieved but it is unknown whether they affect weight loss among African‐American women. The current study examined personal weight loss goals and expected satisfaction with a reasonable weight loss among African‐American women with type 2 diabetes starting a behavioral obesity treatment. We also explored associations among these factors and weight loss treatment outcomes. Self‐identified African‐American women (N = 84) in a 24‐session group program were assessed at baseline and 6‐month follow‐up. At baseline, women indicated weight loss goals of 14.1 ± 6.6 kg (14% of initial weight). They also reported relatively high expected satisfaction with a reasonable weight loss (7–10%). On average, participants lost 3.0 ± 3.9 kg (3% of initial weight) and attended 73 ± 21% of group sessions. Neither weight loss goals nor expected satisfaction with a reasonable weight loss was correlated with either actual weight loss outcome or attendance. Having higher personal weight loss goals was associated with lower expectations of satisfaction with a reasonable weight loss. This suggests that African‐American women with type 2 diabetes enter treatment hoping to lose far more weight than they are likely to achieve. It is important to understand the psychosocial sequelae of failing to reach these goals on subsequent weight maintenance and future weight loss attempts within this population.     

Associations of Fat Distribution and Obesity with Hypertension in a Bi‐ethnic Population: The ARIC Study

Objective: To examine associations of hypertension with obesity and fat distribution among African American and white men and women. Research Methods and Procedures: The analysis sample included 15,063 African American and white men and women between the ages of 45 and 64 years who were participants in the 1987 through 1989 examination of the Atherosclerosis Risk in Communities Study (ARIC). Odds ratios and adjusted prevalences of hypertension were calculated across sexspecific quintiles of body mass index (BMI), waist‐to‐hip ratio (WHR), waist circumference, and waist‐to‐height ratio (waist/height) and adjusted for age, research center, smoking, education, physical activity, alcohol consumption, hormone replacement therapy, and menopausal status. Results: The prevalence of hypertension was higher among African Americans than whites. In the lowest quintile of BMI, 41% of African American women and 43% of African American men had hypertension compared with 14% of white women and 19% of white men. Elevated BMI, WHR, waist circumference, and waist/height were associated with increased odds of hypertension in African American and white men and women. In women, but not in men, there were significant interactions between ethnicity and the anthropometric variables studied here. The direction of the interaction indicated larger odds ratios for hypertension with increasing levels of anthropometric indices in white compared with African American women. Discussion: Obesity and abdominal fat preponderance were associated with increased prevalence of hypertension in African American and white men and women. Associations were similar among African American and white men, but obesity and fat patterning were less strongly associated with hypertension in African American than in white women.     

Is there a link between paternity concern and female genital cutting in West Africa?

Here we explore the relationship between female genital cutting (FGC), sexual behaviour, and marriage opportunities in five West African countries. Using large demographic datasets (n 72,438 women, 12,704 men, 10,695 couples) we explore key (but untested) assumptions of an evolutionary proposal that FGC persists because it provides evolutionary fitness benefits for men by reducing non-paternity rates. We identify and test three assumptions implicit in this proposal. We test whether cut women have reduced extra-pair sex before or within marriage; whether FGC is associated with a younger age at marriage as an indication of partner preference; and whether individual and group-level indicators of paternity concern are associated with a stronger preference for marriage to women with FGC.Our results show that FGC status does not affect the odds of women engaging in several indicators of premarital sex, however women with FGC have significantly lower odds of having more than one lifetime sexual partner. We also show that women with FGC get married at a younger age which supports the argument that FGC status influences women's marriage opportunities, even when it does not restrict sexual activity. Finally, we find that in population groups where reported sexual activity and perceived risk of women's extra-pair sex is high, men have higher odds of marrying a first wife with FGC. Together, these results indicate that paternity certainty may be one of several factors contributing to the persistence of FGC in this sample, and that group-level sexual norms are key to maintaining the practice of FGC through the marriage market.     

Reproduction in Hemophilia

Patterns of marriage and parenthood were studied in the families of 250 patients with severe hemophilia. The incidence of marriage among adult hemophiliacs was 82.5 percent that of age-matched males of the general United States population, as of 1968. Married hemophiliacs 30 years old or older had an average of 2.1 children each, as of 1971. In the periods 1950-1954 and 1960-1964, the numbers of children sired by hemophiliacs were 25 and 38 percent, respectively, of the numbers expected of age-matched men of the general United States population. This indicates a lesser ability or willingness to have children. The number of additional births to women who were already mothers of hemophiliacs was compared with that expected for women of the general population of the United States, matched for age and parity. In the years 1940 through 1954, the birthrates for the two groups were similar. However, in the years 1955-1968, the birthrate among carriers declined more rapidly than that in the general population. The improved medical treatment of hemophilia has apparently not resulted in a greater willingness of affected persons to transmit the defective gene.     

Population demographic structure of the city of Ulan Ude: Ethnic composition and age at marriage

The marriage structure of the population of Ulan Ude, the capital of Buryat Republic, which is characterized by a mixed ethnic composition, has been studied. Differences between Ulan Ude districts in a number of genetic demographic parameters have been found. In ethnic terms, the city district populations differ from one another in the number of ethnic groups and the proportions of the largest groups (Russians and Buryats). In the total Ulan Ude population, the proportions of Russian men and women among persons contracting marriages are 71.44 and 73.79%, respectively; those of Buryat men and women are 23.36 and 22.79%, respectively. The total proportion of all other ethnic groups among both men and women contracting marriages is no more than 5.2%. The mean ages at first marriage in both indigenous and immigrant populations of Ulan Ude are relatively old; these values are 25.9 and 24.72 years for Buryat men and women and 24.86 and 22.69 for non-indigenous men and women, respectively.     

Geographic patterns of genome admixture in Latin American Mestizos

The large and diverse population of Latin America is potentially a powerful resource for elucidating the genetic basis of complex traits through admixture mapping. However, no genome-wide characterization of admixture across Latin America has yet been attempted. Here, we report an analysis of admixture in thirteen Mestizo populations (i.e. in regions of mainly European and Native settlement) from seven countries in Latin America based on data for 678 autosomal and 29 X-chromosome microsatellites. We found extensive variation in Native American and European ancestry (and generally low levels of African ancestry) among populations and individuals, and evidence that admixture across Latin America has often involved predominantly European men and both Native and African women. An admixture analysis allowing for Native American population subdivision revealed a differentiation of the Native American ancestry amongst Mestizos. This observation is consistent with the genetic structure of pre-Columbian populations and with admixture having involved Natives from the area where the Mestizo examined are located. Our findings agree with available information on the demographic history of Latin America and have a number of implications for the design of association studies in population from the region.     

Racial fertility differences: The role of female employment and education in wanted and unwanted childbearing

Abstract

This paper employs data from a merged sample of the National Surveys of Family Growth to examine how female employment status conditions the relationship between education and wanted and unwanted births among African American and white women. A rationale is presented for why a minority group status hypothesis that posits lower fertility among more highly educated African American women as compared to similar white women might find support in the case of wanted births and among certain women, including earlier birth cohorts. Our results provide some evidence for these ideas as well as evidence for a social characteristics hypothesis that predicts convergence of childbearing with rising education. However, persistently higher levels of unwanted births among African American women of all educational levels suggest that the dynamics of racial fertility differences are more complex than either of the hypotheses imply.     

Exogamy and Change in the Biosocial Structure of a Modern Urban Population

Change is traced in the biosocial structure of the Japanese American population of Seattle-King County, Washington, from that of a deme to a state approaching panmixis with surrounding American populations. Data from 2,767 marriage license applications of Japanese Americans between 1930 and 1975 were used to calculate rates of racial exogamy. Rates rose from prewar levels of less than 1% to over 50% in 1975. The total Japanese American county population was subdivided into a nuclear group, tracing its origins back to the original founding immigrants, and a nonnuclear group which has migrated into the area since World War II. Until 1965, the nonnuclear group consistently led the nuclear group in exogamous marriages. In both groups, females consistently out-married more frequently than did the males. Further analysis of community exogamy, i.e., nuclear member marriage to a nonnuclear Japanese American, showed that this type of exogamy within the second generation preceded the high rates of racial exogamy characterizing the marriage patterns of the third generation. Familial analysis suggested that the maternal kin ties of nuclear population females continue to influence marriage choice of their offspring. The patterns of increasing racial exogamy for Japanese Americans are examined against their rise in socioeconomic status, [biosocial structure, exogamy, population]     

Duration between marriage and first birth and marital instability

This paper considers whether marital instability varies by the duration between marriage and 1st birth among ever-married white and black American women. Analysis of data from the June 1985 Current Population Survey suggests that the duration between marriage and 1st birth has a generally monotonic relationship with the probability of white women separating or divorcing from their 1st marriage; the relationship has remained relatively constant over time. For blacks, no consistent association is found between marital dissolution and the duration between marriage and 1st birth. Black women having a premarital conception and postmarital birth and those having their 1st birth during their 2nd year of marriage have a similarly high risk of dissolution. Conversely, blacks having their 1st birth 8-12 or 25-42 months after marrying have a low probability of dissolution. Childless women and those with premarital births generally has the greatest probability of marital disruption for whites. Racial differences may occur because blacks view the 1st birth and marriage differently than whites. That is, because blacks are much more likely to have premarital births and to have a shorter duration between marriage and 1st birth, blacks and whites in the same 1st birth interval category may be dissimilar and have different values resulting in a differential effect of the timing of the 1st birth on marital instability by race. Caution is needed when interpreting the pattern of association between delayed childbearing (and to a lesser extent, births occuring a few years after marriage) and marital instability. Results for whites were similar at each marriage duration and it is assumed delayed childbearing was not a result of marital instability. Marital instability was expected to have its strongest effect on the timing of the 1st birth during the 1st years of marriage. Marital instability may be partially responsible for the delaying of childbearing among blacks. However, blacks who delay but are married at 1st birth have a relatively low risk of separating or divorcing.     

The Relationship between Native American Ancestry,Body Mass Index and Diabetes Risk among Mexican-Americans

Higher body mass index (BMI) is a well-established risk factor for type 2 diabetes, and rates of obesity and type 2 diabetes are substantially higher among Mexican-Americans relative to non-Hispanic European Americans. Mexican-Americans are genetically diverse, with a highly variable distribution of Native American, European, and African ancestries. Here, we evaluate the role of Native American ancestry on BMI and diabetes risk in a well-defined Mexican-American population. Participants were randomly selected among individuals residing in the Houston area who are enrolled in the Mexican-American Cohort study. Using a custom Illumina GoldenGate Panel, we genotyped DNA from 4,662 cohort participants for 87 Ancestry-Informative Markers. On average, the participants were of 50.2% Native American ancestry, 42.7% European ancestry and 7.1% African ancestry. Using multivariate linear regression, we found BMI and Native American ancestry were inversely correlated; individuals with <20% Native American ancestry were 2.5 times more likely to be severely obese compared to those with >80% Native American ancestry. Furthermore, we demonstrated an interaction between BMI and Native American ancestry in diabetes risk among women; Native American ancestry was a strong risk factor for diabetes only among overweight and obese women (OR = 1.190 for each 10% increase in Native American ancestry). This study offers new insight into the complex relationship between obesity, genetic ancestry, and their respective effects on diabetes risk. Findings from this study may improve the diabetes risk prediction among Mexican-American individuals thereby facilitating targeted prevention strategies.     

Stages of Change and Weight Loss Among Rural African American Women

Objective: Obesity is a prevalent public health problem in the United States, especially for rural African American women, and causes increased morbidity and mortality. The purpose of this analysis was to determine whether the transtheoretical stages of change model was generalizable to weight loss intention among overweight and obese rural African American women and to identify important predictors of the stages of change. Research Methods and Procedures: The study was conducted in two rural counties in central Virginia. A population‐based sample of 200 women under the age of 40 completed questionnaires concerning weight loss behavior and beliefs about weight. Ordinal logistic regression was used to predict stage of change. Results: A total of 142 of the 200 women (71%) were overweight or obese (body mass index of ≥25) and were classified into a stage of change. Overall, 30% of respondents were in the precontemplation stage, 15% in the contemplation stage, 48% in the preparation stage, 4% in the action stage, and 3% in the maintenance stage. Education, what friends think about weight, body mass index, and a scale of the positive aspects of weight loss were significant predictors of the stage of change (p < 0.05). Conclusions: Several predictors of stage were the same as those found in studies of other health behaviors, and this research provides support for applying a stages of change model for weight loss intention among rural African American women. Two predictors in particular, significance of what friends think about weight and a scale of the positive aspects of weight loss, have implications for health education initiatives and social support in weight loss interventions.     

Ancestral consanguinity and mortality among three endogamous populations of Chittoor District, Andhra Pradesh, India

Consanguineous marriages have been practiced around the globe by many societies from time immemorial, particularly in South India. Consanguineous marriages play a major role in the health of a population, and diseases leading to mortality of the progeny are a consequence of detrimental recessive genes. To evaluate the effects of ancestral consanguinity on mortality in relation to consanguineous marriage, we have ascertained data from 1,500 women belonging to three endogamous communities (Akuthota Reddy, Odde, and Madiga) of Chittoor District, Andhra Pradesh, India. There were 500 women from each community. For each marriage we drew a family pedigree, extended upward to two earlier generations on either side of the spouses, to determine the prevalence and pattern of consanguinity, with detailed information on fertility and mortality. We observed a significant difference in the mortality rates between consanguineous and nonconsanguineous marriages when all the marriages of the women, women's parents, and (women's) husband's parents were considered in all three communities. In inbreeding, the offspring of earlier generations might have passed on deleterious genes to later generations (under unfavorable conditions), which resulted in a negative aspect of reproduction (among the offspring of the present couple).     

Ethnic differences in adrenocorticotropic hormone, cortisol and corticotropin-releasing hormone during pregnancy

Significant ethnic disparities exist in reproductive outcomes. A potential contributing factor may be the functioning of the hypothalamic-pituitary-adrenal (HPA) axis and placenta during pregnancy. In the present study, levels of cortisol, ACTH and CRH were determined longitudinally from the plasma of 310 African American, Hispanic and non-Hispanic White women at 18-20, 24-26 and 30-32 weeks' gestation. During pregnancy, African American women exhibited lower levels of cortisol than non-Hispanic women and higher levels of ACTH than Hispanic women. The trajectory of CRH increase also differed by ethnicity, with African Americans exhibiting the lowest levels both early and late in pregnancy. Higher levels of cortisol at 18-20 weeks were associated with higher levels of CRH at 30-32 weeks among the African American and Hispanic women, but not among non-Hispanic women. Ethnic differences persisted when adjusting statistically for sociodemographic and biomedical factors. The findings are consistent with the possibility that ethnic disparities in adverse birth outcomes may be due, in part, to differences in HPA axis and placental function.     

Coitus, the proximate determinant of conception: inter-country variance in sub-Saharan Africa

There is a general consensus in the literature that fertility differences between populations can be accounted for by differences in just four key proximate determinants: nuptiality, the postpartum non-susceptible period, contraception and abortion. Natural fecundibility is generally assumed to be constant between populations. This paper puts the theoretical and empirical case for a re-evaluation of that assumption, drawing on the under-utilized data on sexual activity collected in the Demographic Health Surveys (DHSs). Using data for married women in nine African countries, the analysis finds substantial population level differences in mean monthly coital frequency, which, if accurate, suggest an important demographic effect. There is a clear regional patterning to these differences, with levels of activity considerably lower among women in the West African populations included in the study than those from East and southern Africa. For West Africa in particular the data indicate the normality of exceptionally long periods of very infrequent or no intercourse by married women outside the period of postpartum abstinence. The findings challenge prevailing presumptions concerning susceptibility to pregnancy in marriage on which statistics for unmet need for family planning are derived. While doubts are raised over the precision of the sexual activity data used, the paper argues for the need for a greater effort to operationalize the 'proximate determinant of conception', not only for more accurate fertility modelling, but also as a planning tool for a more sensitive provision of family planning services in Africa.     

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.     

Mammography screening and breast self-examination among minority women in public housing projects: the impact of physician recommendation.

This exploratory study examined the impact of physician recommendations and other factors on mammography screening and breast-self examination (BSE) among African American and Hispanic women in public housing communities. We surveyed a randomly selected sample of low-income households from three low-income communities (n = 291), which included both African Americans and Hispanic women. Data for this paper are reported only on women who were 40 years and older head of the households (n = 120 women, including 74 Hispanics and 46 African Americans), since they meet the age criterion for mammography screening. Our analyses indicated that only 46% of women obtained mammography in the previous 12 months, with no significant differences between the Hispanic and African American women in mammography rates. Physicians' recommendations were among the most significant and substantial predictors of obtaining a mammogram or performing BSE. Further, odds were also higher for those who had insurance coverage. In addition, our data also indicated that almost one out of four women, aged 40 and older participants in this study, claimed that their health care providers never told them they needed a mammogram or never told them that they should perform BSE, with no significant differences between Hispanic and African Americans. Our analyses points to an urgent need for intervention to inform and motivate the service providers in underserved communities to motivate breast cancer screening (BCS) among minority women. Additionally, our examination points to the need for urgent interventions targeting minority women, particularly women with no medical insurance for breast cancer screening.