Covariates of age at first birth in Guyana: a hazards model analysis

1987 ◽  
Vol 19 (4) ◽  
pp. 427-438 ◽  
Author(s):  
K. Vaninadha Rao ◽  
Komanduri S. Murty
Keyword(s):  
Fertility Survey ◽  
Age At First Birth ◽  
Birth Cohorts ◽  
Urban Residence ◽  
First Birth ◽  
Number Of Children ◽  
Early Entry ◽  
Hazards Model ◽  
First Birth Timing

SummaryAnalysis of data from the Guyana Fertility Survey on the trends and covariates of age at first birth among various birth cohorts of women ever in union indicates that an early entry into union is associated with young age at first birth and higher number of children born. Multivariate analysis showed that women with highér education, urban residence, and entry into union at age 20 or older among younger cohorts experienced lower risks for first birth compared to others, and that young women are delaying their first birth for longer durations than older women. Work status of women before first birth and the starting age of union seem to be the two major contributory factors for age at first birth. Noticeably, the role of education has changed and is now more significant among younger cohorts than among older ones for first birth timing.

scholarly journals The Role of Fertility in the Demography of Grandparenthood: Evidence from Italy

2020 ◽  
Author(s):  
Giorgio Di Gessa ◽  
Valeria Bordone ◽  
Bruno Arpino
Keyword(s):  
Social Relations ◽  
Intergenerational Transfers ◽  
Later Life ◽  
Age At First Birth ◽  
Birth Cohorts ◽  
Number Of Children ◽  
Italian Survey ◽  
Fertility Differentials ◽  
Compositional Changes

Abstract Grandparents play an important role in their family’s lives. However, little is known about the demography of grandparenthood. Given dramatic recent changes in fertility, we explore the role of number of children and age at first birth in the timing of the transition into grandparenthood focusing on Italy, a country with well-known North-South fertility differentials. We used data from the 2009 Italian Survey ‘Family and Social Relations’ (N = 10,186) to estimate median ages of grandparenthood across three birth cohorts of parents (1920–29; 1930–39; 1940–49). Findings show an overall postponement of age of grandparenthood of 5 years, shifting for women from early to mid- or late-50s (in the South and North, respectively). Such postponement is largely driven by family compositional changes: although the age of grandparenthood among mothers of three or more children has not changed much over cohorts, the percentage of mothers with such characteristic decreased significantly. The heterogeneity in experiencing the transition to grandparenthood has implications for intergenerational transfers and other roles in later life.

Examining the link between religiousness and fitness in a behavioural ecological framework

2019 ◽  
Vol 52 (5) ◽  
pp. 756-767 ◽  
Author(s):  
Janko Međedović
Keyword(s):  
Life History ◽  
Reproductive Success ◽  
Parental Investment ◽  
Life History Theory ◽  
Community Sample ◽  
Future Research ◽  
Harsh Environment ◽  
Age At First Birth ◽  
First Birth ◽  
Number Of Children

AbstractIn recent years there have been attempts to explain religiousness from an evolutionary viewpoint. However, empirical data on this topic are still lacking. In the present study, the behavioural ecological theoretical framework was used to explore the relations between religiousness, harsh environment, fitness (reproductive success and parental investment) and fitness-related outcomes (age at first birth, desired number of children and the romantic relationship duration). The data were collected from 461 individuals from a community sample who were near the end of their reproductive phase (54% females, Mage = 51.75; SD = 6.56). Positive links between religiousness, harsh environment, fitness and fitness-related outcomes were expected, with the exception of age at first birth, for which a negative association was hypothesized. Hence, the main assumption of the study was that religiousness has some attributes of fast life-history phenotypes – that it emerges from a harsh environment and enables earlier reproduction. The study findings partially confirmed these hypotheses. Religiousness was positively related to environmental harshness but only on a zero-order level. Religious individuals had higher reproductive success (this association was especially pronounced in males) but religiousness did not show associations with parental investment. Religiousness was positively associated with desired number of children and negatively associated with age at first birth, although the latter association was only marginally significant in the multivariate analyses. Finally, path analysis showed that desired number of children and age at first birth completely mediated the relation between religiousness and reproductive success. The data confirmed the biologically adaptive function of religiousness in contemporary populations and found the mediating processes that facilitate fitness in religious individuals. Furthermore, the findings initiate a more complex view of religiousness in a life-history context which could be fruitful for future research: a proposal labelled as ‘ontogeny-dependent life-history theory of religiousness’.

scholarly journals Intelligence and Fitness: The Mediating Role of Educational Level

2017 ◽  
Vol 15 (2) ◽  
pp. 147470491770693 ◽  
Author(s):  
Janko Međedović
Keyword(s):  
Reproductive Success ◽  
Cognitive Abilities ◽  
Evolutionary Status ◽  
Age At First Birth ◽  
First Birth ◽  
Short Term ◽  
Number Of Children ◽  
Mediating Role ◽  
Fitness Indicators

The evolutionary status of intelligence is not clear: It is positively related to various indicators of fitness but negatively to reproductive success as the most important fitness marker. In the present research, we explored the links between intelligence and three fitness indicators: number of children (short-term reproductive success), number of grandchildren (long-term reproductive success), and age at first birth. Participants were individuals in a postreproductive stage ( N = 191; mean age = 66.5 years). Intelligence had a positive correlation with short-term reproductive success and age at first birth but a negative correlation with long-term reproductive success. Participants’ education turned out to be a significant mediator of the link between intelligence and criterion measures. The results showed that intelligence can elevate short-term reproductive success. Furthermore, individuals with higher intellectual abilities tended to delay reproduction, which negatively affected their long-term reproductive success. Education was revealed as a very important resource which affects the link between cognitive abilities and fitness, thus proving its evolutionary role in contemporary populations.

Birth Spacing in Pakistan

1988 ◽  
Vol 20 (2) ◽  
pp. 175-194 ◽  
Author(s):  
Zeba Sathar
Keyword(s):  
Birth Spacing ◽  
Fertility Survey ◽  
Age At First Birth ◽  
First Birth ◽  
Marriage Age ◽  
Table Analysis ◽  
Urban Rural ◽  
Independent Effects ◽  
Account Interaction ◽  
Length Of Interval

SummaryLife table analysis is applied to data from the Pakistan Fertility Survey (1975) to examine the effects on birth spacing of a number of socioeconomic variables. Women of more modern backgrounds seem to space their families more closely, but differ little in achieved family size from the more traditional groups. Important factors are age at marriage, age at first birth, province of residence, and whether the woman had ever used contraception. Multivariate analysis taking into account interaction between variables shows that education, urban-rural residence, and province exert independent effects, and so does the cohort of the mother. But the variable with the strongest effect on length of interval, other than that from marriage to first birth, is duration of breast-feeding.

Age at first birth and lifetime fertility

1988 ◽  
Vol 20 (2) ◽  
pp. 167-174 ◽  
Author(s):  
T. R. Balakrishnan ◽  
K. Vaninadha Rao ◽  
Karol J. Krotki ◽  
Evelyne Lapierre-Adamcyk
Keyword(s):  
Older Women ◽  
National Sample ◽  
Fertility Survey ◽  
Age At First Birth ◽  
First Birth ◽  
Younger Women ◽  
Cumulative Fertility ◽  
Catch Up ◽  
Late Starters

SummaryAmong a national sample of Canadian women in the Canadian National Fertility Survey of 1984, the excess cumulative fertility of those who started their families early over others has steadily decreased. A difference of approximately two births between early and late starters among older women is reduced to approximately half a child among the younger women. Except for those who start childbearing after age 25, there is little evidence of attempts to catch up after age 30, irrespective of starting age.

scholarly journals Is the Association Between Education and Fertility Postponement Causal? The Role of Family Background Factors

2017 ◽  
Author(s):  
Felix C Tropf ◽  
Jornt J Mandemakers
Keyword(s):  
Family Environment ◽  
Family Background ◽  
Large Body ◽  
Ordinary Least Squares ◽  
Identical Twin ◽  
Age At First Birth ◽  
Birth Cohorts ◽  
First Birth ◽  
Background Factors ◽  
Twin Model

A large body of literature has demonstrated a positive relationship between education and age at first birth. However, this relationship may be partly spurious because of family background factors that cannot be controlled for in most research designs. We investigate the extent to which education is causally related to later age at first birth in a large sample of female twins from the United Kingdom (N = 2,752). We present novel estimates using within–identical twin and biometric models. Our findings show that one year of additional schooling is associated with about one-half year later age at first birth in ordinary least squares (OLS) models. This estimate reduced to only a 1.5-month later age at first birth for the within–identical twin model controlling for all shared family background factors (genetic and family environmental). Biometric analyses reveal that it is mainly influences of the family environment—not genetic factors—that cause spurious associations between education and age at first birth. Last, using data from the Office for National Statistics, we demonstrate that only 1.9 months of the 2.74 years of fertility postponement for birth cohorts 1944–1967 could be attributed to educational expansion based on these estimates. We conclude that the rise in educational attainment alone cannot explain differences in fertility timing between cohorts.

scholarly journals Schizophrenia risk and reproductive success: a Mendelian randomization study

2019 ◽  
Vol 6 (3) ◽  
pp. 181049 ◽  
Author(s):  
Rebecca B. Lawn ◽  
Hannah M. Sallis ◽  
Amy E. Taylor ◽  
Robyn E. Wootton ◽  
George Davey Smith ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Mendelian Randomization ◽  
Causal Effect ◽  
Sexual Partners ◽  
Age At First Birth ◽  
First Birth ◽  
Genetic Liability ◽  
Number Of Children ◽  
Fitness Advantage ◽  
Number Of Sexual Partners

Schizophrenia is a debilitating and heritable mental disorder associated with lower reproductive success. However, the prevalence of schizophrenia is stable over populations and time, resulting in an evolutionary puzzle: how is schizophrenia maintained in the population, given its apparent fitness costs? One possibility is that increased genetic liability for schizophrenia, in the absence of the disorder itself, may confer some reproductive advantage. We assessed the correlation and causal effect of genetic liability for schizophrenia with number of children, age at first birth and number of sexual partners using data from the Psychiatric Genomics Consortium and UK Biobank. Linkage disequilibrium score regression showed little evidence of genetic correlation between genetic liability for schizophrenia and number of children ( r g = 0.002, p = 0.84), age at first birth ( r g = −0.007, p = 0.45) or number of sexual partners ( r g = 0.007, p = 0.42). Mendelian randomization indicated no robust evidence of a causal effect of genetic liability for schizophrenia on number of children (mean difference: 0.003 increase in number of children per doubling in the natural log odds ratio of schizophrenia risk, 95% confidence interval (CI): −0.003 to 0.009, p = 0.39) or age at first birth (−0.004 years lower age at first birth, 95% CI: −0.043 to 0.034, p = 0.82). We find some evidence of a positive effect of genetic liability for schizophrenia on number of sexual partners (0.165 increase in the number of sexual partners, 95% CI: 0.117–0.212, p = 5.30×10 −10 ). These results suggest that increased genetic liability for schizophrenia does not confer a fitness advantage but does increase mating success.

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