Italian neonatal birthweight charts derived from INeS not separated by birth order.

BACKGROUND: Identifying high-risk neonates with abnormal fetal growth is crucial for health risk prediction and early intervention. Small for gestational age (SGA) and large for gestational age (LGA) classifications highlight neonates having a higher risk for postnatal diseases. Accurate diagnosis depends on precise anthropometric measurements and appropriate reference data. In 2010, specific neonatal charts for Italian singletons (INeS charts) were published, tracing separately for first- and later-born neonates due to a 3% birth weight difference. We present INeS charts for birth weight non-separated by first- and later-born babies useful when information on parity is unavailable or unreliable, or for better comparisons with other neonatal charts that are not separated by birth-order. METHODS: INeS charts were traced using a parametric function. Starting with the parameters estimates published in a different paper, INeS charts not separated by birth order were traced for the gestational age range of 23 to 42 weeks. In a second step the charts were parametrized as Cole and Green Lambda Mu and Sigma (LMS) model, allowing computation of standard deviation scores. RESULTS: The centiles of non-separated INeS charts follow between first- and later-born charts. Distances varied due to changing first-born proportions with gestational age, Max differences of about 100g with later born and 70g with first-born were observed at term. S and L functions have a similar shape for boys and girls. S function shows a pick at about 29 weeks, L function has positive values in all the range of gestational age with a pick at 39 weeks. CONCLUSIONS: The study presents non-separated Birth Weight INeS charts, bridging the gap when parity information is unavailable. Differences with separated charts were generally small, making them reliable for neonatal health assessment. Insights from L and S parameters contribute to standardized birth weight and adjust it by sex and Gestational Age, useful for defining SGA or LGA neonates. The paper enhances neonatal care tools, showcasing INeS chart flexibility in different clinical scenarios and supporting neonatology research.

Parental age at death is associated with age at first birth in offspring.

PURPOSE: People age at different rates and the available evidence suggests that the rate of aging is partly inherited from previous generations. This heterogeneity in aging is evident already in midlife, but to what extent aging is associated with the timing of events earlier in life is not fully known. Here we aim to shed light on this topic by investigating the trade-off between reproduction and aging postulated by evolutionary theories of aging. METHODS: Drawing on the inheritance of aging we use parental age at death as a proxy for aging-rates in the offspring, and study how age at first birth depends on this variable. We use data from an almost complete Swedish birth cohort comprising 92,359 individuals. Accelerated failure time models are used to estimate the association between parental age at death and age at first birth while adjusting for parental occupational class, educational attainment, and income. RESULTS: Longer parental lifespans were consistently associated with older age at first births, both in men and women. CONCLUSION: Our findings suggest that aging-related processes may be interrelated with the processes underlying the timing of reproduction and are in general agreement with evolutionary theories of aging.

Mode of birth in subsequent pregnancy when first birth was vacuum extraction or second stage cesarean section at a tertiary referral hospital in Uganda.

INTRODUCTION: The trends of increasing use of cesarean section (CS) with a decrease in assisted vaginal birth (vacuum extraction or forceps) is a major concern in health care systems all over the world, particularly in low-resource settings. Studies show that a first birth by CS is associated with an increased risk of repeat CS in subsequent births. In addition, CS compared to assisted vaginal birth (AVB), attracts higher health service costs. Resource-constrained countries have low rates of AVB compared to high-income countries. The aim of this study was to compare mode of birth in the subsequent pregnancy among women who previously gave birth by vacuum extraction or second stage CS in their first pregnancy at Mulago National Referral Hospital, Uganda. METHODS: This was a retrospective cohort study that involved interviews of 81 mothers who had a vacuum extraction or second stage CS in their first pregnancy at Mulago hospital between November 2014 to July 2015. Mode of birth in the subsequent pregnancy was compared using Chi-2 square test and a Fisher's exact test with a 0.05 level of statistical significance. RESULTS: Higher rates of vaginal birth were achieved among women who had a vacuum extraction (78.4%) compared to those who had a second stage CS in their first pregnancy (38.6%), p < 0.001. CONCLUSIONS AND RECOMMENDATIONS: Vacuum extraction increases a woman's chance of having a subsequent spontaneous vaginal birth compared to second stage CS. Health professionals need to continue to offer choice of vacuum extraction in the second stage of labor among laboring women that fulfill its indication. This will help curb the up-surging rates of CS.

Sibling comparisons, sibling relationship quality, and perceived sport competence in young athletes.

Siblings are overlooked, yet potentially meaningful social agents in youth sport. To better understand the role of siblings in youth sport, we examined the association between sibling sport-referenced comparisons, relationship qualities, and perceived sport competence. The tendency to make sibling comparisons was expected to be positively related to sport competence perceptions and this association was further expected to be moderated by markers of sibling relationship quality. Participants were 47 sport-involved sibling dyads that included older siblings (25 female, 22 male, Mage = 10.94 ± 1.49 yrs) who were predominately first-born children (83%) and their younger siblings (23 female, 24 male participants, Mage = 8.45 ± 1.01 yrs) who were mostly second-born children (79%). Participants completed established assessments of comparison tendency, sibling relationship qualities, and sport competence perceptions. Analyses revealed a three-way interaction between birth position (younger or older sibling), tendency to compare, and sibling warmth predicting sport competence (p < .05). Younger siblings with a greater tendency to make sibling comparisons and higher warmth perceptions reported higher sport competence perceptions. The findings suggest that sibling-based comparisons and relational warmth may be salient for younger siblings in gauging their competence, whereas older siblings utilize alternative sources of competence information.

Childhood maltreatment and trajectories of cardiometabolic health across the reproductive life span among individuals with a first birth during the Coronary Artery Risk Development in Young Adults Study.

OBJECTIVE: Childhood adversity is associated with poor cardiometabolic health in adulthood; little is known about how this relationship evolves through childbearing years for parous individuals. The goal was to estimate differences in cardiometabolic health indicators before, during and after childbearing years by report of childhood maltreatment in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort study. METHODS: Including 743 individuals nulliparous at baseline (1985-1986) with one or more pregnancies >20 weeks during follow-up (1986-2022), we fit segmented linear regression models to estimate mean differences between individuals reporting or not reporting childhood maltreatment (physical or emotional) in waist circumference, triglycerides, high-density lipoprotein cholesterol, systolic and diastolic blood pressure, fasting glucose, and body mass index (BMI) prior to, during, and following childbearing years using generalized estimating equations, allowing for interaction between maltreatment and time within each segment, and adjusting for total parity, parental education, and race (Black or white, self-reported). RESULTS: Individuals reporting maltreatment (19%; 141) had a greater waist circumference (post-childbearing: +2.9 cm, 95% CI (0.7, 5.0), higher triglycerides [post-childbearing: +8.1 mg/dL, 95% CI (0.7, 15.6)], and lower HDL cholesterol [post-childbearing: -2.1 mg/dL, 95% CI (-4.7, 0.5)] during all stages compared to those not reporting maltreatment. There were not meaningful differences in blood pressure, fasting glucose, or BMI. Individuals who reported maltreatment did not report faster changes over time. CONCLUSION: Differences in some aspects of cardiometabolic health between individuals reporting versus not reporting childhood maltreatment were sustained across reproductive life stages, suggesting potentially persistent impacts of childhood adversity.

A Pregnancy and Childhood Epigenetics Consortium (PACE) meta-analysis highlights potential relationships between birth order and neonatal blood DNA methylation.

Higher birth order is associated with altered risk of many disease states. Changes in placentation and exposures to in utero growth factors with successive pregnancies may impact later life disease risk via persistent DNA methylation alterations. We investigated birth order with Illumina DNA methylation array data in each of 16 birth cohorts (8164 newborns) with European, African, and Latino ancestries from the Pregnancy and Childhood Epigenetics Consortium. Meta-analyzed data demonstrated systematic DNA methylation variation in 341 CpGs (FDR adjusted P < 0.05) and 1107 regions. Forty CpGs were located within known quantitative trait loci for gene expression traits in blood, and trait enrichment analysis suggested a strong association with immune-related, transcriptional control, and blood pressure regulation phenotypes. Decreasing fertility rates worldwide with the concomitant increased proportion of first-born children highlights a potential reflection of birth order-related epigenomic states on changing disease incidence trends.

Birth order and children's health and learning outcomes in India.

India has a high prevalence of stunting among children under five years of age, despite marginal improvement over the years. In 2019-21, 35.5 per cent of children below five years were stunted (National Family Health Survey (NFHS), 2019-21). This has been attributed to several factors including open defecation, poor maternal nutrition and food insecurity. This paper examines if the birth order of children is associated with variation in height among them, using nationally representative data from the India Human Development Survey (IHDS 2005 & 2011). The objectives of this paper are to: (i) assess the association of a child's birth order with height (ii) test if the association of birth order with height changes with the degree of son preference (iii) analyse the relationship between birth order and educational outcomes of children. Our results suggest that (i) the height-for-age z score is negatively associated with the birth order of the child (ii) the negative association of birth order with height is stronger for mothers who have a moderate or high degree of son preference, especially when children have an older brother (iii) maternal characteristics such as education could mitigate the negative relationship between birth order and height when son preference is low but not when son preference is high (iv) birth order has a negative association with the reading, writing and mathematical ability of children, especially if the child was stunted in childhood. This indicates that the fertility behaviour of families has both a direct and an indirect impact, which could influence both long term nutrition and education of children.

The association of family size and birth order in adolescence to the likelihood of developing psychotic disorders in young adulthood: A follow-up study of former adolescent inpatients.

This is a clinical follow-up study of 508 former adolescent psychiatric inpatients admitted to hospital between 2001 and 2006 in Northern Finland. The participants were interviewed using the K-SADS-PL and the EuropASI instruments. Until 2016, the national Finnish Care Register for Health Care provided data on psychiatric diagnoses. Using logistic regression analysis, we examined how birth order and childhood family size affected the incidence of schizophrenia spectrum disorder (SSD) and other psychotic disorders by young adulthood. Participants were separated into three diagnostic subgroups 1) participants with SSD (n = 76), 2) participants with a psychotic disorder other than SSD (n = 107) and 3) participants with only one nonpsychotic depressive episode (n = 118). The main conclusions were that large family size in adolescence (six or more children), male sex and father having psychiatric problems or being unemployed, were significantly associated with a higher likelihood of SSD among study participants. Large family size also associated to a higher likelihood of developing other psychotic disorders. Being the first born or an only child reduced the likelihood of psychotic disorders other than SSD. When diagnosing and treating children and teenagers with psychotic symptoms, information regarding their family size and sibling position may be relevant.

Investigating time to first birth among women of reproductive age in Bangladesh: a survival analysis of nationwide cross-sectional survey data.

BACKGROUND: The birth of the first child is an important turning point in a woman's life as it is the starting point of the demanding responsibilities of motherhood and childcare. This study aimed to explore the waiting time and the significant indicators of time to the first birth of aged 15-49 years of ever-married women in Bangladesh. METHODS: The study considered the most recent country-representative data collected from Bangladesh Demographic and Health Survey (BDHS) in 2017/18. The log-rank test was used to assess the statistical significance of the observed difference between waiting time to first birth and various socio-economic and demographic factors. The Cox proportional hazard model is applied to identify the influential factors for waiting time to first birth. RESULTS: About 55% of the respondents' age at their first birth was less than 18 years. More than 21% of them were 20 years and above at their first birth. Findings revealed a higher mean age at first birth in urban areas than in rural areas. Also, in Dhaka and Sylhet region, women have a higher age at first than in other regions of Bangladesh. Results show that the place of residence, region, age at first marriage, age at first sex, respondent's education, employment status, contraceptive use, and mass media exposure were found to be statistically significant determinants of the age of respondents at the time of first birth. Findings also show that a woman from rural areas was likely to be 5% smaller in age at the time of first birth than their counterpart (aHR 1.05; 95% CI 1.01-1.10). The age at first birth of a woman in Chattogram was 24% shorter, while in Rangpur and Barishal, that age was increased by 14% and 8%, respectively. A woman with no education, primary, and secondary education had 28%, 38%, and 29%, respectively, shorter age at first birth than that of the higher educated women. Mass media unexposed women were shorter aged at first birth by 27% (aHR 1.27; 95% CI 1.10-1.47) compared to the women who were mass media exposed. CONCLUSION: It is necessary to increase the age of mothers at first birth which may help to reduce the prevalence of child marriage in Bangladesh. The study findings will be helpful to the policymakers in identifying the gap and designing the programmes targeting the early timing of first birth to reduce child mortality as well as poor maternal outcomes which will be beneficial for achieving the Sustainable Development Goal-3 in Bangladesh.

The effects of reproductive variables on child mortality in Ethiopia: evidence from demographic and health surveys from 2000 to 2016.

BACKGROUND: Child mortality is a crucial indicator reflecting a country's health and socioeconomic status. Despite significant global improvements in reducing early childhood deaths, Southern Asia and sub-Saharan Africa still bear the highest burden of newborn mortality. Ethiopia is one of five countries that account for half of new-born deaths worldwide. METHODS: This study examined the relationship between specific reproductive factors and under-five mortality in Ethiopia. A discrete-time survival model was applied to analyze data collected from four Ethiopian Demographic and Health Surveys (EDHS) conducted between 2000 and 2016. The study focused on investigating the individual and combined effects of three factors: preceding birth interval, maternal age at childbirth, and birth order, on child mortality. RESULTS: The study found that lengthening the preceding birth interval to 18-23, 24-35, 36-47, or 48+ months reduced the risk of under-five deaths by 30%, 46%, 56%, and 60% respectively, compared to very short birth intervals (less than 18 months). Giving birth between the ages 20-34 and 35+ reduced the risk by 34% and 8% respectively, compared to giving birth below the age of 20. The risk of under-five death was higher for a 7th-born child by 17% compared to a 2nd or 3rd-born child. The combined effect analysis showed that higher birth order at a young maternal age increased the risk. In comparison, lower birth order in older maternal age groups was associated with higher risk. Lastly, very short birth intervals posed a greater risk for children with higher birth orders. CONCLUSION: Not only does one reproductive health variable negatively affect child survival, but their combination has the strongest effect. It is therefore recommended that policies in Ethiopia should address short birth intervals, young age of childbearing, and order of birth through an integrated strategy.

Complementary feeding practices and associated factors among mothers of children aged 6 to 23 months in Sub-saharan African countries: a multilevel analysis of the recent demographic and health survey.

INTRODUCTION: Malnutrition is a public health problem in sub-Saharan Africa with an increased morbidity and mortality rate than in other parts of the world. Poor complementary feeding practices are one of the major causes of malnutrition during the first two years of life. Therefore, this study aimed to determine the prevalence and associated factors of appropriate complementary feeding practices among mothers of children aged 6 to 23 months in sub-Saharan African countries. METHODS: A multilevel mixed-effect analysis was carried out using recent demographic health survey data from 19 sub-Saharan African countries, which were conducted between 2015 and 2020. A total weighted sample of 60,266 mothers of children aged 6 to 23 months were included in the study. The demographic health survey employs a stratified two-stage sampling technique. Data extracted from the recent DHS data sets were cleaned, recorded, and analyzed using STATA/SE version 14.0 statistical software. Multilevel mixed-effects logistic regression was used to determine the factors associated with complementary feeding practice. Variables with a p-value less than 0.05 and adjusted odds ratio (AOR) with a 95% confidence interval (CI) were reported as statistically significant variables associated with appropriate complementary feeding practices. RESULTS: The prevalence of appropriate complementary feeding practices among mothers of children aged 6 to 23 months in sub-Saharan African countries was 13.02% (95% CI: 12.75-13.29%). Maternal educational level [AOR = 0.69, 95% CI (0.64, 0.74)] and [AOR = 0.52, 95% CI (0.47, 0.57)], marital status of the mother [AOR = 0.85, 95% CI (0.74, 0.96)], sex of household head [AOR = 1.78, 95% CI (1.09, 1.27)], total children ever born [AOR = 1.52, 95% CI (1.18, 1.96)], [AOR = 1.43, 95% CI (1.14, 1.81)], and [AOR = 1.31, 95% CI (1.04, 1.64)], media exposure [AOR = 0.74, 95% CI (0.69, 0.79)], ANC visits attended during pregnancy [AOR = 0.73, 95% CI (0.63, 0.80)] and [AOR = 0.67, 95% CI (0.62, 0.74)], place of delivery [AOR = 0.92, 95% CI (0.85, 0.98)], currently breastfeeding [AOR = 1.12, 95% CI (1.01, 1.23)], PNC checkup [AOR = 0.75, 95% CI (0.70, 0.80)], the current age of the child [AOR = 0.26, 95% CI (0.24, 0.28)] and [AOR = 0.14, 95% CI (0.13, 0.16)], birth order [AOR = 1.31, 95% CI (1.09, 1.58)], number of under 5 children in the household [AOR = 0.76, 95% CI (0.59, 0.97)], community illiteracy [AOR = 1.09, 95% CI (1.02, 1.18)], and country category [AOR = 1.62, 95% CI (1.18, 2.22)] were significantly associated with appropriate complementary feeding practices. CONCLUSION: The prevalence of appropriate complementary feeding practices among mothers of children aged 6 to 23 months in sub-Saharan Africa was relatively low. Higher maternal educational level, female household head, having media exposure, attending more ANC visits, health facility delivery, currently breastfeeding, having PNC follow-up, low community illiteracy, and living in the West Africa region increase the odds of appropriate complementary feeding practices. Women empowerment, increasing maternal health services accessibility, promoting breastfeeding behavior, increasing media exposure of the household, and improving the proportion of health facility delivery are strongly recommended.

Compliance towards WHO recommendations on antenatal care for a positive pregnancy experience: Timeliness and adequacy of antenatal care visit in Sub-Saharan African countries: Evidence from the most recent standard Demographic Health Survey data.

BACKGROUND: Timely and adequate antenatal care (ANC) visits are known to reduce maternal mortality by 20%. Despite the World Health Organization updating its recommendations from four to eight antenatal care contacts, data reporting in the SSA region focused primarily on four visits, and evidence on the timing and adequacy of ANC based on the current recommendation was limited. Hence, this study aimed at assessing the level of timely and adequate ANC visits and their determinants in the 18 Sub-Saharan African countries with the most recent DHS report (2016-2021). METHODS: The data for this study were pooled from the most recent standardized Demographic and Health Survey data of sub-Saharan African countries from 2016-2021. A total of 171,183 (with a weighted frequency of 171,488) women were included and analyzed by using STATA version 16. To account for data clustering, a multivariable multilevel mixed-effect logistic regression analysis was run to determine the effects of each predictor on the receipt of timely and adequate ANC. Adjusted odds ratio with its corresponding 95% confidence interval was used to declare the statistical significance of the independent variables. RESULTS: The receipt of timely and adequate antenatal care visits was 41.2% (95% CI: 40.9, 41.4) and 10.4% (95% CI: 9.9, 10.2), respectively. Wontedness of pregnancy [AOR = 1.18; 95% CI: 1.13, 1.24], being 1st birth order [AOR = 1.48; 95% CI: 1.41, 2.54], having a mobile phone [AOR = 1.49; 95% CI: 1.26, 2.32], and enrolled in Health insurance schemes [AOR = 2.03; 95% CI: 1.95, 2.42] were significantly associated with early initiation of ANC. Living in a lower community poverty level[AOR = 2.23; 95% CI: 1.90,2.66], being in the richest wealth quintile [AOR = 1.49; 95% CI: 1.36, 1.62], higher educational level [AOR = 3.63; 95% CI: 3.33, 3.96], the timing of ANC visit [AOR = 4.26; 95% CI: 4.08, 4.44], being autonomous in decision making [AOR = 2.29; 95% CI: 1.83, 2.54] and having a mobile phone [AOR = 1.89; 95% CI: 1.76, 2.52] were identified as significant predictors of adequate ANC uptake. CONCLUSION: The findings revealed a low coverage of timely and adequate ANC visits in SSA countries. Governments and healthcare managers in sub-Saharan African countries should leverage their efforts to prioritize and implement activities and interventions that increase women's autonomy, and economic capability, to improve their health-seeking behavior during pregnancy. More commitment is needed from governments to increase mobile phone distribution across countries, and then work on integrating mHealth into their health system. Finally, efforts should be made to increase the coverage of health insurance schemes enrolment for the citizens.

Spatial patterns and determinants of low utilization of delivery care service and postnatal check-up within 2 months following birth in Ethiopia: Bivariate analysis.

BACKGROUND: Home delivery is a nonclinical childbirth practice that takes place in one's home with or without traditional birth attendants and postnatal care is the care given to the mother and her newborn baby; according to world health organization (WHO), the postnatal phase, begins one hour after birth and lasts six weeks (42 days). This paper aimed to study the spatial pattern and determinant factors of low utilization of delivery care (DC) services and postnatal check-up (PNC) after live births in Ethiopia. METHODS: This study used the 2016 Ethiopian Demographic and Health Survey data as a source. A total weighted samples of 11023 women-children pairs were included. The bivariate binary logistic regression analyses with spatial effect were modeled using SAS version 9.4 and ArcGIS version 10.8 was used for mapping. RESULTS: The spatial distribution of low utilization of delivery care service and postnatal check-up were significantly clustered in Ethiopia (Moran's I statistic 0.378, P-value < 0.001 and 0.177, P-value < 0.001 respectively). Among 11023 children-women pair, the prevalence of home delivery and no postnatal check-up within two months following birth were 72.6% and 91.4% respectively. The Liben, Borena, Guji, Bale, Dolo and Zone 2 were predicted to have high prevalence of home delivery and part of Afder, Shabelle, Korahe, Dolo and Zone 2 were high risk areas of no postnatal checkup. CONCLUSION AND RECOMMENDATIONS: Lack of occupation, region, large family size, higher birth order, low utilization of antenatal care visit, unable to access mass media, big problem of health facility distance and the spatial variable were found to be jointly significant predictors of low utilization of DC and PNC in Ethiopia. Whereas older age, being reside in rural area and low wealth status affects delivery care service utilization. We suggest health providers, policy makers and stakeholders consider those variables with priority given to Liben, Borena, Guji, Bale, Dolo, Zone 2, Afder, Shabelle and Korahe, where home delivery and no PNC were predicted relatively high. We also recommend researchers to conduct further studies using latest survey data set.

Second-versus first-born twin: comparison of short- and long-term outcomes.

PURPOSE: An ancient description of the competition between twins for first breath is found in the biblical story of Jacob and Esau (Genesis 25:26) when Jacob pulled his older brother's heel in the hope of becoming firstborn but to no avail. In this study, we sought to evaluate the short and long-term outcomes of twin pairs, comparing between the second- and first-born twin. METHODS: A population-based cohort study, including dichorionic twin deliveries occurring between the years 1991 and 2021 at Soroka University Medical Center. A General estimation equation (GEE) was applied to adjust for confounders. The incidence of offspring's hospitalizations due to various medical conditions was compared. Kaplan-Meier survival analyses compared cumulative morbidity. Cox proportional hazards models were used to control for confounders. RESULTS: 5507 twin deliveries met the inclusion criteria. Second-born twins had higher rates of cesarean deliveries, statistically significant in the GEE multivariable analysis. More first-twin fetuses were experiencing non-reassuring fetal heart rate patterns, although other obstetrical outcomes as well as mortality rates were comparable between groups. Second twins weighed lower than their older sibling (mean difference 33 g) and were more frequently SGA and low birthweight (1500-2500 g); (p < 0.05). Later during childhood, offspring of twin deliveries experienced notable morbidity due to infectious (23.8-24.1%), respiratory (10.5-10.9%), neurological (7.0-7.8%) and cardiovascular pathologies (1.7-1.9%) during childhood, that was unaffected by birth order. CONCLUSION: Other than birthweight differences, the birth order of dichorionic twins is not associated with adverse neonatal health indices, nor does it predict excess risk for morbidity during childhood.

Does the Fraternal Birth Order Effect Influence Handedness?

The fraternal birth order effect (FBOE) is the phenomenon whereby the probability that a man has a same-sex sexual orientation in adulthood increases with each biological older brother. Several studies have found evidence that the FBOE is limited to right-handed men, and left-handed men do not show an FBOE. Recent debates about the appropriate methods for quantifying the FBOE center on distinguishing the FBOE from other effects, such as the female fecundity effect (FFE), whereby mothers more prone to bearing gay sons are also more fecund. The FBOE and FFE are confounded in that a real FFE will result in data consistent with the FBOE under some analyses. Here, we applied some recent proposed analytic methods for the FBOE to the property of handedness. A straightforward application of Khovanova's technique to the binary trait of handedness yielded support for a fraternal birth order effect consistent with the maternal immune hypothesis, in that the ratios of handedness differed between men with one older brother only, and men with one younger brother only, while no such effect was seen in women. This effect was not seen, however, when the confounding effects of parental age were controlled for. Models including factors to simultaneously test multiple posited effects find significant female fecundity effects, as well as paternal age and birth order effects on handedness in men, but no FBOE. The effects seen in women were different, with no fecundity or parental age effects, but birth order and sex of older siblings had effects. We conclude, based on this evidence, that many of the factors thought to contribute to sexual orientation in men may also have an influence on handedness, and further note that parental age is a potential confound which may be overlooked by some analyses of the FBOE.

Birth-order effects on risk taking are limited to the family environment.

Why is the empirical evidence for birth-order effects on human psychology so inconsistent? In contrast to the influential view that competitive dynamics among siblings permanently shape a person's personality, we find evidence that these effects are limited to the family environment. We tested this context-specific learning hypothesis in the domain of risk taking, using two large survey datasets from Germany (SOEP, n = 19,994) and the United States (NLSCYA, n = 29,627) to examine birth-order effects on risk-taking propensity across a wide age range. Specification-curve analyses of a sample of 49,621 observations showed that birth-order effects are prevalent in children aged 10-13 years, but that they decline with age and disappear by middle adulthood. The methodological approach shows the effect is robust. We thus replicate and extend previous work in which we showed no birth-order effects on adult risk taking. We conclude that family dynamics cause birth-order effects on risk taking but that these effects fade as siblings transition out of the home.

Sibling effects on problem and prosocial behavior in childhood: Patterns of intrafamilial "contagion" by birth order.

We investigated longitudinal relations between siblings' problem and prosocial behavior, measured by the Strengths and Difficulties Questionnaire, among different sibship sizes in the UK's Millennium Cohort Study. We identified 3436 families with two children and 1188 families with three children. All children (cohort members and their older sibling [OS]) had valid data on behavior at two time points (in 2004 and 2006). Using structural equation model, we found that for internalizing and externalizing problems, OSs (MOS1 = 6.3 years, MOS2 = 9.1 years at T1) exerted a dominant effect on younger siblings (Mage = 3.12 years at T1; 49.7% boys) across sibship sizes. For prosocial behavior, there was OS dominance in two-child families and youngest sibling dominance in three-child families.

Age at first birth is associated with the likelihood of frailty in middle-aged and older women: A population-based analysis from NHANES 1999-2018.

OBJECTIVES: This study examined whether age at first birth (AFB) is associated with the prevalence of frailty in middle-aged and older women. METHODS: The study included 10,828 women (age ≥ 45 years) from the National Health and Nutrition Examination Survey (NHANES) (1999-2018) in the United States. AFB data were collected using a standardized reproductive health questionnaire. Frailty was measured using a 53-item frailty index and was diagnosed if the score on that index was over 0.21. Survey-weighted logistic regression models were used to assess the association between AFB and the prevalence of frailty. A survey-weighted restricted cubic spline (RCS) model was used to determine the dose-response relationship between AFB and frailty. Mediation analyses were performed to estimate the mediated effects of education levels, family poverty income ratio, and parity on the association between AFB and the likelihood of frailty. Finally, sensitivity and subgroup analyses were conducted to validate the robustness of our findings. RESULTS: Among the 10,828 women, 3828 (35.4 %) had frailty. The RCS depicted a U-shaped association between AFB and frailty. Compared with the women in the reference group (AFB: 33-35 years), women in the other groups (AFB: < 18, 18-20, 21-23, and 24-26 years) had a higher likelihood of frailty, with respective odds ratios (95 % confidence intervals) of 3.02 (1.89-4.83), 2.32 (1.54-3.50), 1.83 (1.19-2.81), and 1.64 (1.07-2.53). However, no statistically significant differences were detected for women with AFB of 27-29, 30-32, or > 35 years compared with the reference group. Education levels, family poverty income ratio, and parity significantly mediated the approximately linear negative association between AFB and frailty in the subset of women with AFB of ≤32 years and the mediation proportions were 23.4 %, 32.4 %, and 18.3 %, respectively (all p < 0.001). CONCLUSIONS: Based on our results, we conclude that early AFB is associated with a higher likelihood of frailty in middle-aged and older women.

Male androphilia, fraternal birth order, and female fecundity in Samoa: A 10-y retrospective.

Two separate but related literatures have examined familial correlates of male androphilia (i.e., sexual attraction and arousal to masculine adult males). The fraternal birth order effect (FBOE) is a widely established finding that each biological older brother a male has increased the probability of androphilia 20-35% above baseline rates. Other family demographic variables, such as reproduction by mothers, maternal aunts, and grandmothers, have been used to test evolutionary hypotheses that sexually antagonistic genes lead to androphilia among males, lowering or eliminating reproduction, which is offset by greater reproductive output among their female relatives. These proposed female fecundity effects (FFEs), and the FBOE, have historically been treated as separate yet complementary ways to understand the development and evolution of male androphilia. However, this approach ignores a vital confound within the data. The high overall reproductive output indicative of an FFE results in similar statistical patterns as the FBOE, wherein women with high reproductive output subsequently produce later-born androphilic sons. Thus, examination of the FBOE requires analytic approaches capable of controlling for the FFE, and vice-versa. Here, we present data simultaneously examining the FBOE and FFE for male androphilia in a large dataset collected in Samoa across 10 y of fieldwork, which only shows evidence of the FBOE.

A deep phenotyping approach to assess the association of handedness, early life factors and mental health.

The development of handedness and other form of functional asymmetries is not yet understood in its critical determinants. Early life factors (e.g., birth weight, birth order) have been discussed to contribute to individual manifestations of functional asymmetries. However, large-scale data such as the UK Biobank suggest that the variance in handedness that is explained by early life factors is minimal. Additionally, atypical handedness has been linked to clinical outcomes such as neurodevelopmental and psychiatric disorders. Against the background of this triad, the current study investigated associations between different forms of functional asymmetries and (a) early life factors as well as (b) clinical outcomes. Functional asymmetries were determined by means of a deep phenotyping approach which notably extends previous work. In our final sample of N = 598 healthy participants, the different variables were tested for associations by means of linear regression models and group comparisons (i.e., ANOVAs and Chi-squared tests). Confirming previous findings from larger cohorts with shallow phenotyping, we found that birth factors do not explain a substantial amount of variance in functional asymmetries. Likewise, functional asymmetries did not seem to have comprehensive predictive power concerning clinical outcomes in our healthy participants. Future studies may further investigate postulated relations in healthy and clinical samples while acknowledging deep phenotyping of laterality.