Evolutionary perspectives on pregnancy: maternal age at menarche and infant birth weight

Childhood adversity and accelerated reproductive events: a systematic review and meta-analysis

OBJECTIVE

Accelerated female reproductive events represent the early onset of reproductive events involving puberty, menarche, pregnancy loss, first sexual intercourse, first birth, parity, and menopause. This study aimed to explore the association between childhood adversity and accelerated female reproductive events.

DATA SOURCES

PubMed, Web of Science, and Embase were systematically searched from September 22, 2022 to September 23, 2022.

STUDY ELIGIBILITY CRITERIA

Observational cohort, cross-sectional, and case-control studies in human populations were included if they reported the time of reproductive events for female individuals with experience of childhood adversity and were published in English.

METHODS

Two reviewers independently screened studies, obtained data, and assessed study quality, and conflicts were resolved by a third reviewer. Dichotomous outcomes were evaluated using meta-analysis, and pooled odds ratios and 95% confidence intervals were generated using random-effects models. Moderation analysis and meta-regression were used to investigate heterogeneity.

RESULTS

In total, 21 cohort studies, 9 cross-sectional studies, and 3 case-control studies were identified. Overall, female individuals with childhood adversity were nearly 2 times more likely to report accelerated reproductive events than those with no adversity exposure (odds ratio, 1.91; 95% confidence interval, 1.33-2.76; I2=99.6%; P<.001). Moderation analysis indicated that effect sizes for the types of childhood adversity ranged from an odds ratio of 1.61 (95% confidence interval, 1.23-2.09) for low socioeconomic status to 2.13 (95% confidence interval, 1.14-3.99) for dysfunctional family dynamics. Among the 7 groups based on different reproductive events, including early onset of puberty, early menarche, early sexual initiation, teenage childbirth, preterm birth, pregnancy loss, and early menopause, early sexual initiation had a nonsignificant correlation with childhood adversity (odds ratio, 2.70; 95% confidence interval, 0.88-8.30; I2=99.9%; P<.001). Considerable heterogeneity (I2>75%) between estimates was observed for over half of the outcomes. Age, study type, and method of data collection could explain 35.9% of the variance.

CONCLUSION

The literature tentatively corroborates that female individuals who reported adverse events in childhood are more likely to experience accelerated reproductive events. This association is especially strong for exposure to abuse and dysfunctional family dynamics. However, the heterogeneity among studies was high, requiring caution in interpreting the findings and highlighting the need for further evaluation of the types and timing of childhood events that influence accelerated female reproductive events.

The human biology of spaceflight

To expand the human exploration footprint and reach Mars in the 2030s, we must explore how humans survive and thrive in demanding, unusual, and novel ecologies (i.e., extreme environments). In the extreme conditions encountered during human spaceflight, there is a need to understand human functioning and response in a more rigorous theoretically informed way. Current models of human performance in space-relevant environments and human space science are often operationally focused, with emphasis on acute physiological or behavioral outcomes. However, integrating current perspectives in human biology allows for a more holistic and complete understanding of how humans function over a range of time in an extreme environment. Here, we show how the use of evolution-informed frameworks (i.e., models of life history theory to organize the adaptive pressures of spaceflight and biocultural perspectives) coupled with the use of mixed-methodological toolkits can shape models that better encompass the scope of biobehavioral human adjustment to long-duration space travel and extra-terrestrial habitation. Further, we discuss how we can marry human biology perspectives with the rigorous programmatic structures developed for spaceflight to model other unknown and nascent extremes.

Maternal Age at Menarche Genes Determines Fetal Growth Restriction Risk

We aimed to explore the potential link of maternal age at menarche (mAAM) gene polymorphisms with risk of the fetal growth restriction (FGR). This case (FGR)-control (FGR free) study included 904 women (273 FGR and 631 control) in the third trimester of gestation examined/treated in the Departments of Obstetrics. For single nucleotide polymorphism (SNP) multiplex genotyping, 50 candidate loci of mAAM were chosen. The relationship of mAAM SNPs and FGR was appreciated by regression procedures (logistic/model-based multifactor dimensionality reduction [MB-MDR]) with subsequent in silico assessment of the assumed functionality pithy of FGR-related loci. Three mAAM-appertain loci were FGR-linked to genes such as KISS1 (rs7538038) (effect allele G-odds ratio (OR)allelic = 0.63/pperm = 0.0003; ORadditive = 0.61/pperm = 0.001; ORdominant = 0.56/pperm = 0.001), NKX2-1 (rs999460) (effect allele A-ORallelic = 1.37/pperm = 0.003; ORadditive = 1.45/pperm = 0.002; ORrecessive = 2.41/pperm = 0.0002), GPRC5B (rs12444979) (effect allele T-ORallelic = 1.67/pperm = 0.0003; ORdominant = 1.59/pperm = 0.011; ORadditive = 1.56/pperm = 0.009). The haplotype ACA FSHB gene (rs555621*rs11031010*rs1782507) was FRG-correlated (OR = 0.71/pperm = 0.05). Ten FGR-implicated interworking models were founded for 13 SNPs (pperm ≤ 0.001). The rs999460 NKX2-1 and rs12444979 GPRC5B interplays significantly influenced the FGR risk (these SNPs were present in 50% of models). FGR-related mAAM-appertain 15 polymorphic variants and 350 linked SNPs were functionally momentous in relation to 39 genes participating in the regulation of hormone levels, the ovulation cycle process, male gonad development and vitamin D metabolism. Thus, this study showed, for the first time, that the mAAM-appertain genes determine FGR risk.

Exploring Adaptive Phenotypes for the Human Calcium-Sensing Receptor Polymorphism R990G

Rainforest hunter-gatherers from Southeast Asia are characterized by specific morphological features including a particularly dark skin color (D), short stature (S), woolly hair (W), and the presence of steatopygia (S)-fat accumulation localized in the hips (DSWS phenotype). Based on previous evidence in the Andamanese population, we first characterized signatures of adaptive natural selection around the calcium-sensing receptor gene in Southeast Asian rainforest groups presenting the DSWS phenotype and identified the R990G substitution (rs1042636) as a putative adaptive variant for experimental follow-up. Although the calcium-sensing receptor has a critical role in calcium homeostasis by directly regulating the parathyroid hormone secretion, it is expressed in different tissues and has been described to be involved in many biological functions. Previous works have also characterized the R990G substitution as an activating polymorphism of the calcium-sensing receptor associated with hypocalcemia. Therefore, we generated a knock-in mouse for this substitution and investigated organismal phenotypes that could have become adaptive in rainforest hunter-gatherers from Southeast Asia. Interestingly, we found that mouse homozygous for the derived allele show not only lower serum calcium concentration but also greater body weight and fat accumulation, probably because of enhanced preadipocyte differentiation and lipolysis impairment resulting from the calcium-sensing receptor activation mediated by R990G. We speculate that such differential features in humans could have facilitated the survival of hunter-gatherer groups during periods of nutritional stress in the challenging conditions of the Southeast Asian tropical rainforests.

Maternal Age at Menarche Gene Polymorphisms Are Associated with Offspring Birth Weight

In this study, the association between maternal age at menarche (AAM)-related polymorphisms and offspring birth weight (BW) was studied. The work was performed on a sample of 716 pregnant women and their newborns. All pregnant women underwent genotyping of 50 SNPs of AAM candidate genes. Regression methods (linear and Model-Based Multifactor Dimensionality Reduction (MB-MDR)) with permutation procedures (the indicator p_perm was calculated) were used to identify the correlation between SNPs and newborn weight (transformed BW values were analyzed) and in silico bioinformatic examination was applied to assess the intended functionality of BW-associated loci. Four AAM-related genetic variants were BW-associated including genes such as POMC (rs7589318) (β_additive = 0.202/p_perm = 0.015), KDM3B (rs757647) (β_recessive = 0.323/p_perm = 0.005), INHBA (rs1079866) (β_additive = 0.110/p_perm = 0.014) and NKX2-1 (rs999460) (β_recessive = -0.176/p_perm = 0.015). Ten BW-significant models of interSNPs interactions (p_perm ≤ 0.001) were identified for 20 polymorphisms. SNPs rs7538038 KISS1, rs713586 RBJ, rs12324955 FTO and rs713586 RBJ-rs12324955 FTO two-locus interaction were included in the largest number of BW-associated models (30% models each). BW-associated AAM-linked 22 SNPs and 350 proxy loci were functionally related to 49 genes relevant to pathways such as the hormone biosynthesis/process and female/male gonad development. In conclusion, maternal AMM-related genes polymorphism is associated with the offspring BW.

Early adversity and the development of explore-exploit tradeoffs

Childhood adversity can have wide-ranging and long-lasting effects on later life. But what are the mechanisms that are responsible for these effects? This article brings together the cognitive science literature on explore-exploit tradeoffs, the empirical literature on early adversity, and the literature in evolutionary biology on 'life history' to explain how early experience influences later life. We propose one potential mechanism: early experiences influence 'hyperparameters' that determine the balance between exploration and exploitation. Adversity might accelerate a shift from exploration to exploitation, with broad and enduring effects on the adult brain and mind. These effects may be produced by life-history adaptations that use early experience to tailor development and learning to the likely future states of an organism and its environment.

The association between maternal stature and adverse birth outcomes and the modifying effect of race and ethnicity: a population-based retrospective cohort study

BACKGROUND

There are known differences in the risk of perinatal and maternal birth outcomes because of maternal factors, such as body mass index and maternal race. However, the association of maternal height with adverse birth outcomes and the potential differences in this relationship by race and ethnicity have been understudied.

OBJECTIVE

This study aimed to examine the association between maternal stature and adverse perinatal outcomes and the potential modification of the association by race and ethnicity.

STUDY DESIGN

This retrospective cohort study was conducted using data on all singleton births in the United States in 2016 and 2017 (N=7,361,713) obtained from the National Center for Health Statistics. Short and tall stature were defined as <10th and >90th percentiles of the maternal height distribution (<154.9 and >172.7 cm, respectively). Race and ethnicity categories included non-Hispanic White, non-Hispanic Black, American Indian or Alaskan Native Asian or Pacific Islander, and Hispanic. The primary outcomes were preterm birth (<37 weeks of gestation), perinatal death, and composite perinatal death or severe neonatal morbidity. Logistic regression was used to obtain adjusted odds ratios and 95% confidence intervals with adjustment for confounding by maternal age, body mass index, and other factors. Multiplicative and additive effect modifications by race and ethnicity were assessed.

RESULTS

The study population included 7,361,713 women with a singleton stillbirth or live birth. Short women had an increased risk of adverse outcomes, whereas tall women had a decreased risk relative to average-stature women. Short women had an increased risk of perinatal death and composite perinatal death or severe neonatal morbidity (adjusted odds ratios, 1.14 [95% confidence interval, 1.10-1.17] and 1.21 [95% confidence interval, 1.19-1.23], respectively). The association between short stature and perinatal death was attenuated in non-Hispanic Black women compared with non-Hispanic White women (adjusted odds ratio, 1.10 [95% confidence interval, 1.03-1.17] vs 1.26 [95% confidence interval, 1.19-1.33]). Compared with average-stature women, tall non-Hispanic White women had lower rates of preterm birth, perinatal death, and composite perinatal death or severe neonatal morbidity (adjusted odds ratios, 0.82 [95% confidence interval, 0.81-0.83], 0.95 [95% confidence interval, 0.91-1.00], and 0.90 [95% confidence interval, 0.88-0.93], respectively). The association between tall and average stature with perinatal death was reversed in Hispanic women (adjusted odds ratio, 1.27; 95% confidence interval, 1.12-1.44). Compared with average-stature women, all tall women had lower rates of preterm birth, particularly among non-Hispanic Black and Hispanic women.

CONCLUSION

Relative to average-stature women, short women have an increased risk of adverse perinatal outcomes across all race and ethnicity groups; these associations were attenuated in Hispanic women and for some adverse outcomes in non-Hispanic Black and Asian women. Tall mothers have a lower risk of preterm birth in all racial and ethnic groups, whereas tall non-Hispanic White mothers have a lower risk of perinatal death or severe neonatal morbidity compared with average-stature women.

Precocious puberty under stressful conditions: new understanding and insights from the lessons learnt from international adoptions and the COVID-19 pandemic

Neuro-biological variations in the timing of sexual maturation within a species are part of an evolved strategy that depend on internal and external environmental conditions. An increased incidence of central precocious puberty (CPP) has been described in both adopted and "covid-19 pandemic" children. Until recently, it was hypothesised that the triggers for CPP in internationally adopted children were likely to be better nutrition, greater environmental stability, and improved psychological wellbeing. However, following data collected during and after the coronavirus (COVID-19) global pandemic, other possibilities must be considered. In a society with high levels of child wellbeing, the threat to life presented by an unknown and potentially serious disease and the stressful environment created by lockdowns and other public health measures could trigger earlier pubertal maturation as an evolutionary response to favour early reproduction. The main driver for increased rates of precocious and rapidly progressive puberty during the pandemic could have been the environment of "fear and stress" in schools and households. In many children, CPP may have been triggered by the psychological effects of living without normal social contact, using PPE, being near adults concerned about financial and other issues and the fear of getting ill. The features and time of progression of CPP in children during the pandemic are similar to those observed in adopted children. This review considers the mechanisms regulating puberty with a focus on neurobiological and evolutionary mechanisms, and analyses precocious puberty both during the pandemic and in internationally adopted children searching for common yet unconsidered factors in an attempt to identify the factors which may have acted as triggers. In particular, we focus on stress as a potential factor in the early activation of the hypothalamic-pituitary-gonadal axis and its correlation with rapid sexual maturation.

Do unwanted children face growth penalties in resource poor environments? Evidence from Roma Settlements in Serbia

In a high fertility context, research on the relationship between parental investment, unwanted births and child nutritional outcomes is limited. The implications may be especially relevant for children coming from the most disadvantaged backgrounds and at increased risk of nutritional deprivation. This study assessed the association between maternal investment, unwanted births disaggregated into mistimed and unwanted children, and child nutritional outcomes in a poor population of Serbian Roma. Multiple Indicator Cluster Surveys rounds 5 and 6 data for Serbian Roma settlements were used to account for the association between two measures of maternal investment: weight at birth and parity, and mistimed and unwanted children, and children height-for-age z-score (HAZ), weight-for-age z score (WAZ) and weight-for- height z-score (WHZ). The sample included 130 children aged 0-24 months. The child variables were age, gender, and birth order, while maternal independent variables included age, literacy and access to improved toilet facility as proxies for socioeconomic status. Children born with low birth weight (lower maternal investment in utero) face a significant deficit in terms of their nutritional outcomes, measured by HAZ and WAZ. The effect was aggravated for height if the child was unwanted while there was a positive relationship between access to improved toilet facility and WHZ. Unwanted children were of higher birth order, with older, higher parity mothers than mistimed children. Many of the Roma children may be at risk of undernutrition, however, Roma children who received lower maternal investment in utero, unwanted and living in poorest households may face additional risk.

Why and how does early adversity influence development? Toward an integrated model of dimensions of environmental experience

Two extant frameworks - the harshness-unpredictability model and the threat-deprivation model - attempt to explain which dimensions of adversity have distinct influences on development. These models address, respectively, why, based on a history of natural selection, development operates the way it does across a range of environmental contexts, and how the neural mechanisms that underlie plasticity and learning in response to environmental experiences influence brain development. Building on these frameworks, we advance an integrated model of dimensions of environmental experience, focusing on threat-based forms of harshness, deprivation-based forms of harshness, and environmental unpredictability. This integrated model makes clear that the why and the how of development are inextricable and, together, essential to understanding which dimensions of the environment matter. Core integrative concepts include the directedness of learning, multiple levels of developmental adaptation to the environment, and tradeoffs between adaptive and maladaptive developmental responses to adversity. The integrated model proposes that proximal and distal cues to threat-based and deprivation-based forms of harshness, as well as unpredictability in those cues, calibrate development to both immediate rearing environments and broader ecological contexts, current and future. We highlight actionable directions for research needed to investigate the integrated model and advance understanding of dimensions of environmental experience.

What is the expected human childhood? Insights from evolutionary anthropology

In psychological research, there are often assumptions about the conditions that children expect to encounter during their development. These assumptions shape prevailing ideas about the experiences that children are capable of adjusting to, and whether their responses are viewed as impairments or adaptations. Specifically, the expected childhood is often depicted as nurturing and safe, and characterized by high levels of caregiver investment. Here, we synthesize evidence from history, anthropology, and primatology to challenge this view. We integrate the findings of systematic reviews, meta-analyses, and cross-cultural investigations on three forms of threat (infanticide, violent conflict, and predation) and three forms of deprivation (social, cognitive, and nutritional) that children have faced throughout human evolution. Our results show that mean levels of threat and deprivation were higher than is typical in industrialized societies, and that our species has experienced much variation in the levels of these adversities across space and time. These conditions likely favored a high degree of phenotypic plasticity, or the ability to tailor development to different conditions. This body of evidence has implications for recognizing developmental adaptations to adversity, for cultural variation in responses to adverse experiences, and for definitions of adversity and deprivation as deviation from the expected human childhood.

Associations between distinct dimensions of early life adversity and accelerated reproductive strategy among middle-aged women in China

BACKGROUND

Life history theory argues that unpredictable and harsh conditions such as early life adversity tends to produce a fast life history strategy, characterized by early sexual maturation and less parenting of offspring. It remains unclear whether all forms of early life adversity are associated with accelerated reproductive strategy, and most previous studies predominantly focused on single form of reproductive strategy indicators.

OBJECTIVE

To examine the associations between 2 distinct dimensions of early life adversity (ie, threat and deprivation) and reproductive strategies across global metrics.

STUDY DESIGN

We used data from 9674 middle-aged women of the China Health and Retirement Longitudinal Study. The experiences of threat and deprivation were assessed using the Life History Survey Questionnaire in 2014. Reproductive strategy information was assessed via self-report from the follow-up of 2013, 2015 and 2018, including age at menarche, age at natural menopause, age at first birth, total number of children, and number of abortions. Multivariate linear regression analyses were performed to assess the associations between distinct dimensions of early life adversity and multiple reproductive strategy indicators, adjusting for age, Hukou location, family socioeconomic status in adulthood and body mass index.

RESULTS

Of the 9674 women (mean [standard deviation] age at baseline, 55.89 [10.23] years), 4084 (42.20%) reported exposure to threat-related early life adversity and 7332 (75.79%) reported exposure to deprivation-related early life adversity. Early life adversity characterized by threat was associated with accelerated reproductive strategy. Compared with women who have no experiences of threat-related early life adversity, ≥3 threat-related early life adversity was associated with 3.7-month earlier age at menarche (β=-0.31, 95% confidence interval, -0.53 to -0.08; P=.007), 8.6-month earlier age at natural menopause (β=-0.72, 95% confidence interval, -1.29 to -0.15; P=.013), >1-year earlier age at first birth (β=-1.14, 95% confidence interval, -1.58 to -0.71; P<.0001), and an increased total number of children (β=0.25, 95% confidence interval, 0.10-0.41; P=.002). In contrast, experiences of deprivation were associated with delayed age at natural menopause (β=.50, 95% confidence interval, 0.06-0.94; P=.025) and increased number of abortions (β=.17, 95% confidence interval, 0.01-0.34, P=.037), in models adjusting for co-occurring threat exposures.

CONCLUSION

This study suggests that early life adversity characterized by threat was associated with accelerated reproductive strategy, whereas deprivation was associated with slower reproduction strategy. Future research should clarify the biological pathways between different dimensions of early life adversity and reproductive strategies and further determine whether accelerated reproduction is an adaptive response to early life adversity in humans.

Change of pace: How developmental tempo varies to accommodate failed provision of early needs

The interplay of genes and environments (GxE) is a fundamental source of variation in behavioral and developmental outcomes. Although the role of developmental time (T) in the unfolding of such interactions has yet to be fully considered, GxE operates within a temporal frame of reference across multiple timescales and degrees of biological complexity. Here, we consider GxExT interactions to understand adversity-induced developmental acceleration or deceleration whereby environmental conditions hasten or hinder children's development. To date, developmental pace changes have been largely explained through a focus on the individual: for example, how adversity "wears down" aging biological systems or how adversity accelerates or decelerates maturation to optimize reproductive fitness. We broaden such theories by positing shifts in developmental pace in response to the parent-child dyad's capacity or incapacity for meeting children's early, physiological and safety needs. We describe empirical evidence and potential neurobiological mechanisms supporting this new conceptualization of developmental acceleration and deceleration. We conclude with suggestions for future research on the developmental consequences of early adverse exposures.

Compromised maternal nutritional status in early pregnancy and its relation to the birth size in young rural Indian mothers

BACKGROUND

Low birth weight is highly prevalent in rural India. As a chronic undernutrition problem, poor birth outcomes are closely related to various nutritional factors more prominently the poor maternal anthropometry at conception. The purpose of the study was to identify how compromised maternal nutritional status in early pregnancy affects the birth size of rural Indian mothers.

METHODS

It was a prospective observational study on singleton pregnant women (n = 204) from 14 villages in Mulshi Taluka of Pune District, Maharashtra, India. Maternal weight (Wt), height (Ht), body fat percent (BF%), head circumference (HC), and sitting height (SHT) were measured at early pregnancy (< 13 weeks of gestation) and infants' weight and length were measured within 24 h of birth. Groups means were tested using a 't' test while the trend in means was tested using ANOVA.

RESULTS

Mothers were young (21.46 ± 2.09 yrs), thin (46.46 ± 6.1 kg), short (153.39 ± 5.79 cm), and poorly nourished (19.74 ± 2.41 kg/m2). Mean birth weight was low (2655 ± 507 g) and prevalence of LBW and stunting at birth was highest among mothers in the lower tertile of each of the anthropometric indicators. In particular, stunting was significantly higher for mothers in lower tertile compared to higher tertile of Wt (44.6 Vs 64.6%) and was also true for HC (43.7 Vs 60.6%). Risk for LBW and stunting at birth was almost similar and was significant (p < 0.01) for mothers in the lower tertile of Wt, Ht, BMI, SHT, HC, and BF% as compared to those in the higher tertile of these measurements.

CONCLUSION

All the anthropometric indicators of current undernutrition at first trimester as well as that in utero reflected by smaller HC, impose risk for LBW and stunting at birth especially among young rural mothers.

Age at menarche and risk of adverse obstetric outcomes during the first childbirth in Japan: The Japan Environment and Children's Study

AIM

Age at menarche is used as a risk indicator of gestational diabetes mellitus, preterm birth, and fetal growth. However, little is known regarding the age impact on obstetric outcomes among nulliparous women. This study investigated whether menarche age was correlated with obstetric outcomes among nulliparous women.

METHODS

We analyzed the data obtained for 37 645 singleton pregnancies between 2011 and 2014 in the Japan Environment and Children's Study. Age at menarche was categorized into the ≤9-, 10-, 11-, 12-, 13-, 14-, and ≥15-year-old groups (n = 363, 3155, 8390, 11 164, 6713, 5446, and 2414, respectively). We calculated the relative risk for cases of preterm birth <37 weeks, low birthweight <2500 g, small for gestational age, early and late-onset hypertension disorders of pregnancy, and early- and late-diagnosed (diagnosed < or ≧ 24 weeks) gestational diabetes mellitus using a reference of 12 years at menarche.

RESULTS

Women with an age at menarche ≤9 years showed an increased incidence of developing early-diagnosed gestational diabetes mellitus (relative risk: 2.42; 95% confidence interval: 1.05-5.60). A high body mass index before pregnancy increased the risk of developing gestational diabetes mellitus.

CONCLUSIONS

Age at menarche helped in assessing the risk of early-diagnosed gestational diabetes mellitus among nulliparous women. Future studies are needed to clarify the underlying mechanisms. This study is the first to use data from the largest prospective birth cohort study of Japan and to investigate the relationship between menarche age and obstetric outcomes among nulliparous women.

Heterozygosity of the major histocompatibility complex predicts later self-reported pubertal maturation in men

Individual variation in the age of pubertal onset is linked to physical and mental health, yet the factors underlying this variation are poorly understood. Life history theory predicts that individuals at higher risk of mortality due to extrinsic causes such as infectious disease should sexually mature and reproduce earlier, whereas those at lower risk can delay puberty and continue to invest resources in somatic growth. We examined relationships between a genetic predictor of infectious disease resistance, heterozygosity of the major histocompatibility complex (MHC), referred to as the human leukocyte antigen (HLA) gene in humans, and self-reported pubertal timing. In a combined sample of men from Canada (n = 137) and the United States (n = 43), MHC heterozygosity predicted later self-reported pubertal development. These findings suggest a genetic trade-off between immunocompetence and sexual maturation in human males.

Historical Context Changes Pathways of Parental Influence on Reproduction: An Empirical Test from 20th-Century Sweden

Several studies have found that parental absences in childhood are associated with individuals’ reproductive strategies later in life. However, these associations vary across populations and the reasons for this heterogeneity remain debated. In this paper, we examine the diversity of parental associations in three ways. First, we test whether different kinds of parental availability in childhood and adolescence are associated with women’s and men’s ages at first birth using the intergenerational and longitudinal Uppsala Birth Cohort Study (UBCoS) dataset from Sweden. This cultural context provides a strong test of the hypothesis that parents influence life history strategies given that robust social safety nets may buffer parental absences. Second, we examine whether investments in education help explain why early parental presence is associated with delayed ages at first birth in many post-industrial societies, given that parents often support educational achievement. Third, we compare parental associations with reproductive timing across two adjacent generations in Sweden. This historical contrast allows us to control for many sources of heterogeneity while examining whether changing educational access and norms across the 20th-century change the magnitude and pathways of parental influence. We find that parental absences tend to be associated with earlier first births, and more reliably so for women. Many of these associations are partially mediated by university attendance. However, we also find important differences across cohorts. For example, the associations with paternal death become similar for sons and daughters in the more recent cohort. One possible explanation for this finding is that fathers start influencing sons and daughters more similarly. Our results illustrate that historical changes within a population can quickly shift how family affects life history.

Early age at menarche and risk of postpartum hemorrhage: a retrospective study in Chinese women

Objective: The objective of this study is to investigate whether early age at menarche is associated with increased risk of postpartum hemorrhage among Chinese women.Materials and methods: Clinical data from 6,383 Chinese women who gave birth to live singleton infants at The First Affiliated Hospital of Chengdu Medical College between October 2016 and October 2019 were extracted from the electronic medical records system. Patients were categorized into four groups according to their age at menarche (≤12, 13, 14 and ≥15 years). Logistic regression analysis was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for postpartum hemorrhage for the different menarche age groups.Results: After controlling for potential confounders, women with menarche at an early age (≤12 years) had a significantly higher risk of developing postpartum hemorrhage than women with an age at menarche of 13 years, and the ORs (95% CIs) for postpartum hemorrhage across the menarche age categories (≤12, 13, 14 and ≥15 years) were 1.27 (1.02-1.81), 1.00 (reference), 0.95 (0.61-1.57), and 0.91 (0.51-1.58), respectively. Moreover, age at menarche was inversely associated with the risk of postpartum hemorrhage after adjustment for all relevant confounding factors, and the OR (95% CI) for postpartum hemorrhage per year of increasing in the age at menarche was 0.93 (0.74-0.99).Conclusion: Early age at menarche was associated with a significantly increased risk of postpartum hemorrhage after adjustment for known confounding factors. This finding could help obstetricians and midwives to identify pregnant women at higher risk of developing postpartum hemorrhage, and allow early preventative strategies to be implemented.

Child Wantedness and Low Weight at Birth: Differential Parental Investment among Roma

Studies investigating child wantedness, birthweight and parental care are limited. This study assessed relationships of child wantedness, low birthweight and differential parental investment in a poor population of Serbian Roma. Data from the Multiple Indicator Cluster Survey round 5 for Roma settlements were used to account for the association between child wantedness and birthweight, and three measures of parental investment: breastfeeding practices, immunization of children and quality of mother-child interaction. The sample included 584 children aged 0-24 months. The child variables were gender, birth order, birthweight (low birthweight at <2500 g and normal birthweight at >2500 g) and whether the child was wanted, while maternal independent variables included age, literacy and household wealth. The results show that unwanted children were at greater risk of having low birthweight. After controlling for birthweight, child wantedness emerged as a predictor of breastfeeding practices and immunization status: Roma mothers biased their investment toward children who were wanted. The quality of mother-child interaction varied with the mother's household wealth. Given the high rates of infant and child mortality among Roma, investments in children's health should be prioritized within the family, where maternal bias in parental investment may contribute to their children's health disparities.

Effect of Psychotherapy on Reduction of Fear of Childbirth and Pregnancy Stress: A Randomized Controlled Trial

Introduction

The fear of childbirth (FOC) has an adverse effect on the physical and mental health of pregnant women and increases adverse maternal and fetal outcomes. Previous research reported the effect of psychological interventions such as cognitive behavioral therapy, relaxation therapies, and short-term psycho-educational intervention on FOC. We examined whether adding motivational interviewing (MI) psychotherapy to prenatal usual care (PUC) is superior to PUC alone to reduce the scores of FOC, pregnancy stress, and self-efficacy.

Materials and Methods

An RCT with two-arm parallel groups and 1:1 allocation ratio assigned 70 pregnant women (aged 18–50) attending public health centers in an education hospital in Iran to receive five sessions of group MI psychotherapy plus PUC (N = 35) or to receive PUC alone (N = 35). The primary outcomes were the FOC scores (Wijma Delivery Expectancy/Experience Questionnaire, W-DEQ), pregnancy-specific stress (Prenatal Distress Questionnaire, NuPDQ), anxiety (Spielberger state anxiety), and Childbirth Self-Efficacy Index (CBSI) at 5 weeks post-randomization. Additional measures included subscales of the W-DEQ and the NuPDQ, patients’ compliance, and satisfaction with psychotherapy intervention at 5 weeks post-randomization as secondary outcomes.

Main Results

The post-trial results indicated that the outcome scores diminished more considerably in psychotherapy than in PUC for total FOC scale with a large effect size (B = −23.54, p = < 0.001, η²η² = 0.27), for total pregnancy stress with a large effect size (B = −4.51, p = < 0.001, η² = 19), and for state anxiety with a large effect size (B = −12.42, p = < 0.001, η² = 0.22). However, the score of self-efficacy and concern about physical symptoms did not differ between the psychotherapy and PUC groups (P < 0.05).

Discussion

Adding 5 weeks of group psychotherapy to PUC could be considered as an adjunctive care option for reducing FOC, pregnancy stress, and general anxiety in pregnant women in the third trimester. Future research may focus on sustaining the effects and evaluating the economic impacts of adding psychotherapy to PUC.

Child volunteers in a women's paramilitary organization in World War II have accelerated reproductive schedules

Understanding how conditions experienced during development affect reproductive timing is of considerable cross-disciplinary interest. Life-history theory predicts that organisms will accelerate reproduction when future survival is unsure. In humans, this can be triggered by early exposure to mortality. Previous studies, however, have been inconclusive due to several confounds that are also likely to affect reproduction. Here we take advantage of a natural experiment in which a population is temporarily divided by war to analyze how exposure to mortality affects reproduction. Using records of Finnish women in World War II, we find that young girls serving in a paramilitary organization wait less time to reproduce, have shorter inter-birth intervals, and have more children than their non-serving peers or sisters. These results support the hypothesis that exposure to elevated mortality rates during development can result in accelerated reproductive schedules and adds to our understanding of how participation in warfare affects women.

Life history theory predicts that females will adjust reproductive timing in response to environmental challenges. Here the authors show that young girls exposed to higher mortality rates during war give birth earlier and more often than their peers who were not exposed to these conditions.

Maternal age at menarche and offspring body mass index in childhood

Background

Earlier age of menarche has been associated with an increased risk of chronic diseases during adulthood, but whether early menarche has intergenerational effect is not clear.

Methods

In this population-based cross-sectional study, we recruited children from 26 primary schools using cluster random probability sampling in Shanghai, China, in 2014. We used multiple linear regression models to estimate the adjusted associations of maternal age of menarche (MAM) with offspring body mass index (BMI). We also used the mediation analysis to examine the contribution of maternal BMI and gestational diabetes to offspring BMI.

Results

A total of 17,571 children aged 6–13 years were enrolled, of whom 16,373 had their weight and height measured. Earlier MAM was associated with higher child BMI in boys (− 0.05 z-score per year older MAM, 95% CI − 0.08 to − 0.02) and in girls (− 0.05 z-score per year older MAM, 95% CI − 0.07 to − 0.02). Maternal BMI positively mediated the association of MAM with offspring BMI in both sexes, with mediation effects of 37.7 and 19.4% for boys and girls, respectively.

Conclusion

Early maternal menarche was associated with greater offspring BMI. This study provides evidence for the intergenerational effect in the development of BMI in offspring.

Electronic supplementary material

The online version of this article (10.1186/s12887-019-1659-4) contains supplementary material, which is available to authorized users.

Preterm birth in evolutionary context: a predictive adaptive response?

Preterm birth is a significant public health problem worldwide, leading to substantial mortality in the newborn period, and a considerable burden of complications longer term, for affected infants and their carers. The fact that it is so common, and rates vary between different populations, raising the question of whether in some circumstances it might be an adaptive trait. In this review, we outline some of the evolutionary explanations put forward for preterm birth. We specifically address the hypothesis of the predictive adaptive response, setting it in the context of the Developmental Origins of Health and Disease, and explore the predictions that this hypothesis makes for the potential causes and consequences of preterm birth. We describe how preterm birth can be triggered by a range of adverse environmental factors, including nutrition, stress and relative socioeconomic status. Examining the literature for any associated longer-term phenotypic changes, we find no strong evidence for a marked temporal shift in the reproductive life-history trajectory, but more persuasive evidence for a re-programming of the cardiovascular and endocrine system, and a range of effects on neurodevelopment. Distinguishing between preterm birth as a predictive, rather than immediate adaptive response will depend on the demonstration of a positive effect of these alterations in developmental trajectories on reproductive fitness. This article is part of the theme issue 'Developing differences: early-life effects and evolutionary medicine'.

Cross-cultural evidence does not support universal acceleration of puberty in father-absent households

Father absence in early life has been shown to be associated with accelerated reproductive development in girls. Evolutionary social scientists have proposed several adaptive hypotheses for this finding. Though there is variation in the detail of these hypotheses, they all assume that family environment in early life influences the development of life-history strategy, and, broadly, that early reproductive development is an adaptive response to father absence. Empirical evidence to support these hypotheses, however, has been derived from WEIRD (Western, Educated, Industrialized, Rich and Democratic) populations. Data from a much broader range of human societies are necessary in order to properly test adaptive hypotheses. Here, we review the empirical literature on father absence and puberty in both sexes, focusing on recent studies that have tested this association beyond the WEIRD world. We find that relationships between father absence and age at puberty are more varied in contexts beyond WEIRD societies, and when relationships beyond the father-daughter dyad are considered. This has implications for our understanding of how early-life environment is linked to life-history strategies, and for our understanding of pathways to adult health outcomes, given that early reproductive development may be linked to negative health outcomes in later life This article is part of the theme issue 'Developing differences: early-life effects and evolutionary medicine'.

Paternal investment and low birth weight - The mediating role of parity

According to life-history theory, paternal investment affects the well-being of offspring. We hypothesized that environmental stress caused by a lack of paternal investment may diminish maternal resource allocation during pregnancy, especially for women who already have dependent children. Our study was conducted on a representative group of more than 80,500 singleton, live-born, full-term infants born in Krakow, Poland in the period 1995-2009. Birth data were obtained from the birth registry. We found that missing data about fathers (a proxy measure of low paternal investment) was associated with higher probability of multiparous mothers giving birth to low-birth-weight infants (1.48; 95% CI 1.05-2.08), but this was not the case with primiparous mothers (1.19; 95% CI 0.89-1.59). The statistically significant synergistic effect between parity and paternal investment was found (Synergy Factor = 2.12; 95% CI 1.47-3.05, p<0.001). These findings suggest that in situations of low paternal investment, multiparous mothers face trade-offs between investing in existing versus unborn children, therefore investment in the latter is lower. Such a strategy may benefit maternal fitness due to investment in older children, who have higher reproductive value.

Developmental Adaptation to Stress: An Evolutionary Perspective

The assumption that early stress leads to dysregulation and impairment is widespread in developmental science and informs prevailing models (e.g., toxic stress). An alternative evolutionary–developmental approach, which complements the standard emphasis on dysregulation, proposes that early stress may prompt the development of costly but adaptive strategies that promote survival and reproduction under adverse conditions. In this review, we survey this growing theoretical and empirical literature, highlighting recent developments and outstanding questions. We review concepts of adaptive plasticity and conditional adaptation, introduce the life history framework and the adaptive calibration model, and consider how physiological stress response systems and related neuroendocrine processes may function as plasticity mechanisms. We then address the evolution of individual differences in susceptibility to the environment, which engenders systematic person–environment interactions in the effects of stress on development. Finally, we discuss stress-mediated regulation of pubertal development as a case study of how an evolutionary–developmental approach can foster theoretical integration.

Age at menarche and prevalence of preterm birth: Results from the Healthy Baby Cohort study

Little is known about the impact of age at menarche on preterm birth. The aim of this study was to examine the association between age at menarche and preterm birth. A total of 11,016 Chinese women who gave birth to live singleton infants were recruited from the Healthy Baby Cohort between 2012 and 2014 in the province of Hubei, China. Age at menarche was reported via face-to-face interviews and was categorized into five groups (≤11, 12, 13, 14 and ≥15 years). Gestational age was estimated using maternal last menstrual period. Preterm birth was defined as delivering a live singleton infant at <37 weeks' gestational age. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Earlier menarche (≤11 years) was associated with an increased prevalence of preterm birth (OR: 1.67, 95% CI: 1.18, 2.36) compared with menarche age at 13 years after controlling for the potential confounders. The findings of our study suggested that a history of earlier menarche might be useful for identifying women at higher risk of preterm birth.

Transcriptome assembly and candidate genes involved in nutritional programming in the swordtail fish Xiphophorus multilineatus

BACKGROUND

Nutritional programming takes place in early development. Variation in the quality and/or quantity of nutrients in early development can influence long-term health and viability. However, little is known about the mechanisms of nutritional programming. The live-bearing fish Xiphophorus multilineatus has the potential to be a new model for understanding these mechanisms, given prior evidence of nutritional programming influencing behavior and juvenile growth rate. We tested the hypotheses that nutritional programming would influence behaviors involved in energy homeostasis as well gene expression in X. multilineatus.

METHODS

We first examined the influence of both juvenile environment (varied in nutrition and density) and adult environment (varied in nutrition) on behaviors involved in energy acquisition and energy expenditure in adult male X. multilineatus. We also compared the behavioral responses across the genetically influenced size classes of males. Males stop growing at sexual maturity, and the size classes of can be identified based on phenotypes (adult size and pigment patterns). To study the molecular signatures of nutritional programming, we assembled a de novo transcriptome for X. multilineatus using RNA from brain, liver, skin, testis and gonad tissues, and used RNA-Seq to profile gene expression in the brains of males reared in low quality (reduced food, increased density) and high quality (increased food, decreased density) juvenile environments.

RESULTS

We found that both the juvenile and adult environments influenced the energy intake behavior, while only the adult environment influenced energy expenditure. In addition, there were significant interactions between the genetically influenced size classes and the environments that influenced energy intake and energy expenditure, with males from one of the four size classes (Y-II) responding in the opposite direction as compared to the other males examined. When we compared the brains of males of the Y-II size class reared in a low quality juvenile environment to males from the same size class reared in high quality juvenile environment, 131 genes were differentially expressed, including metabolism and appetite master regulator agrp gene.

DISCUSSION

Our study provides evidence for nutritional programming in X. multilineatus, with variation across size classes of males in how juvenile environment and adult diet influences behaviors involved in energy homeostasis. In addition, we provide the first transcriptome of X. multilineatus, and identify a group of candidate genes involved in nutritional programming.

Developmental influences on fertility decisions by women: an evolutionary perspective

Developmental environments are crucial for shaping our life course. Elements of the early social and biological environments have been consistently associated with reproduction in humans. To date, a strong focus has been on the relationship between early stress, earlier menarche and first child birth in women. These associations, found predominately in high-income countries, have been usefully interpreted within life-history theory frameworks. Fertility, on the other hand--a missing link between an individual's early environment, reproductive strategy and fitness--has received little attention. Here, we synthesize this literature by examining the associations between early adversity, age at menarche and fertility and fecundity in women. We examine the evidence that potential mechanisms such as birth weight, childhood body composition, risky health behaviours and developmental influences on attractiveness link the early environment and fecundity and fertility. The evidence that menarche is associated with fertility and fecundity is good. Currently, owing to the small number of correlational studies and mixed methodologies, the evidence that early adversity predicts fecundity and fertility is not conclusive. This area of research is in its infancy; studies examining early adversity and adult fertility decisions that can also examine likely biological, social and psychological pathways present opportunities for future fertility research.

Mechanisms linking energy balance and reproduction: impact of prenatal environment

The burgeoning field of metabolic reproduction regulation has been gaining momentum due to highly frequent discoveries of new neuroendocrine factors regulating both energy balance and reproduction. Universally throughout the animal kingdom, energy deficits inhibit the reproductive axis, which demonstrates that reproduction is acutely sensitive to fuel availability. Entrainment of reproductive efforts with energy availability is especially critical for females because they expend large amounts of energy on gestation and lactation. Research has identified an assortment of both central and peripheral factors involved in the metabolic regulation of reproduction. From an evolutionary perspective, these mechanisms likely evolved to optimize reproductive fitness in an environment with an unpredictable food supply and regular bouts of famine. To be effective, however, the mechanisms responsible for the metabolic regulation of reproduction must also retain developmental plasticity to allow organisms to adapt their reproductive strategies to their particular niche. In particular, the prenatal environment has emerged as a critical developmental window for programming the mechanisms responsible for the metabolic control of reproduction. This review will discuss the current knowledge about hormonal and molecular mechanisms that entrain reproduction with prevailing energy availability. In addition, it will provide an evolutionary, human life-history framework to assist in the interpretation of findings on gestational programming of the female reproductive function, with a focus on pubertal timing as an example. Future research should aim to shed light on mechanisms underlying the prenatal modulation of the adaptation to an environment with unstable resources in a way that optimizes reproductive fitness.

Experimentally induced stress decreases ideal female reproductive timing

Previous correlational research shows that childhood adversity is associated with earlier age of reproduction in humans and other species. Such studies, however, cannot show that stressful conditions cause earlier reproduction. Using the cold-pressor task, we built on previous work to test the idea that acute stress influences human reproductive and marital ideals, and that individual stress responses depend on adaptive life history strategies shaped by exposure to adversity during childhood. Acute stress shifted ideal ages of first birth and marriage to earlier ages. We also tested a competing hypothesis, whether stress had a more general impact on time preference, but found no evidence that it did. Furthermore, there was an interaction between childhood adversity and acute stress. Individuals who reported more exposure to childhood adversity responded to acute stress by reporting even earlier reproductive ideals. These findings offer experimental evidence that physiological stress can alter reproductive decision making in humans.

Early stress predicts age at menarche and first birth, adult attachment, and expected lifespan

Life history theory suggests that in risky and uncertain environments the optimal reproductive strategy is to reproduce early in order to maximize the probability of leaving any descendants at all. The fact that early menarche facilitates early reproduction provides an adaptationist rationale for our first two hypotheses: that women who experience more risky and uncertain environments early in life would have (1) earlier menarche and (2) earlier first births than women who experience less stress at an early age. Attachment theory and research provide the rationale for our second two hypotheses: that the subjective early experience of risky and uncertain environments (insecurity) is (3) part of an evolved mechanism for entraining alternative reproductive strategies contingent on environmental risk and uncertainty and (4) reflected in expected lifespan. Evidence from our pilot study of 100 women attending antenatal clinics at a large metropolitan hospital is consistent with all four hypotheses: Women reporting more troubled family relations early in life had earlier menarche, earlier first birth, were more likely to identify with insecure adult attachment styles, and expected shorter lifespans. Multivariate analyses show that early stress directly affected age at menarche and first birth, affected adult attachment in interaction with expected lifespan, but had no effect on expected lifespan, where its original effect was taken over by interactions between age at menarche and adult attachment as well as age at first birth and adult attachment. We discuss our results in terms of the need to combine evolutionary and developmental perspectives and the relation between early stress in general and father absence in particular.

Prenatal smoking and age at menarche: influence of the prenatal environment on the timing of puberty

STUDY QUESTION

Do prenatal exposure to cigarette smoking and birthweight influence age at menarche (AAM) in a cohort of Australian girls?

SUMMARY ANSWER

We find that prenatal smoke exposure and lower birthweight increase the chance of earlier menarche in accordance with theoretical predictions as do confounding factors of maternal AAM and higher BMI of the girls.

WHAT IS KNOWN ALREADY

Much prior research focuses on the role of the early childhood environment in determining AAM but fewer studies consider the role of the prenatal environment. Those studies that examine the prenatal period find an acceleration of maturation associated with maternal smoking and low birthweight. Life history theory predicts that early life exposure to stressful environments should promote more rapid maturation and that this timing can be established before birth, making the prenatal environment particularly important.

STUDY DESIGN, SIZE, DURATION

Statistical analysis of longitudinal survey data collected from a large cohort (n = 2446) of Australian children using data from birth to 12-13 years of age.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Owing to missing data, 1493 girls were included in the final analysis. Using cox regression, we examine how (i) maternal cigarette smoking during gestation and (ii) birthweight influence girls' AAM. Cox regression was used because not all girls had reached menarche.

MAIN RESULTS AND THE ROLE OF CHANCE

We find that older maternal AAM (hazards ratio (HR): 0.75, confidence interval (CI) (95%): 0.71-0.79) and higher birthweight (HR: 0.86, CI (95%): 0.75-0.97) lower the chance of earlier menarche; while higher girls' BMI at 8-9 years (HR: 1.12, CI (95%): 1.10-1.15), and maternal cigarette smoking on 'most days' during gestation (HR: 1.40, CI (95%): 1.10-1.79 with 'no smoking' as the reference level) increased the chance of earlier menarche. All factors were statistically significant at P = 0.05.

LIMITATIONS, REASONS FOR CAUTION

Not all girls had reached menarche, necessitating the use of cox regression. As with other longitudinal studies, there was study sample attrition and some missing data, particularly in reports of maternal smoking. In addition, as the degree of bias in the missing data is unknown, possible inaccurate reporting of maternal smoking may influence the results of birthweight on AAM.

WIDER IMPLICATIONS OF THE FINDINGS

Because of the association between younger AAM and higher risk of uterine, endometrial and breast cancer development, our finding adds to the need to consider the stress caused by prenatal smoke exposure as an important health risk. In addition, this study needs to be extended, when the same girls are 14-15 years of age, and on a larger dataset from a younger cohort within the same Australian Government project.

STUDY FUNDING/COMPETING INTERESTS

No funding was received for this study and there are no competing interests to declare.

Fetal exposure to maternal depressive symptoms is associated with cortical thickness in late childhood

BACKGROUND

Maternal depression is one of the most common prenatal complications. The consequences of fetal exposure to maternal depression are poorly understood. The aim of this study is to examine the association between fetal exposure to maternal depressive symptoms and cortical thickness in children 6-9 years old.

METHODS

A prospective, longitudinal study of maternal depressive symptoms at 19, 25, and 31 weeks' gestation was followed by acquisition of a structural magnetic resonance imaging scan in 81 children (age, 86.1 ± 9.9 months).

RESULTS

Significant (p < .01) cortical thinning in children primarily in the right frontal lobes was associated with exposure to prenatal maternal depression. The strongest association was at 25 weeks' gestation; exposure to maternal depression at 25 gestational weeks was associated with cortical thinning in 19% of the whole cortex and 24% of the frontal lobes, primarily in the right superior, medial orbital, and frontal pole regions of the prefrontal cortex (p < .01). The significant association between prenatal maternal depression and child externalizing behavior (p < .05) was mediated by cortical thinning in prefrontal areas of the right hemisphere.

CONCLUSIONS

The pattern of cortical thinning in children exposed to prenatal maternal depression is similar to patterns in depressed patients and in individuals with risk for depression. Exposure to prenatal depression coupled with subsequent cortical thinning was associated with presence of externalizing behavior in preadolescent children and may be prodromal markers of risk for dysphoria. Vulnerability to prenatal influences at 25 gestational weeks may result from the enormous growth and dramatic structural changes in the nervous system.

The effect of mother's age and other related factors on neonatal survival associated with first and second birth in rural, Tanzania: evidence from Ifakara health and demographic surveillance system in rural Tanzania

BACKGROUND

With a view to improve neonatal survival, data on birth outcomes are critical for planning maternal and child health care services. We present information on neonatal survival from Ifakara Health and Demographic Surveillance System (HDSS) in Tanzania, regarding the influence of mother's age and other related factors on neonatal survival of first and second births.

METHODS

The study conducted analysis using longitudinal health and demographic data collected from Ifakara HDSS in parts of Kilombero and Ulanga districts in Morogoro region. The analysis included first and second live births that occurred within six years (2004-2009) and the unit of observation was a live birth. A logistic regression model was used to assess the influence of socio-demographic factors on neonates' survival.

RESULTS

A total of 18,139 first and second live births were analyzed. We found neonatal mortality rate of 32 per 1000 live births (95% CI: 29/1000-34/1000). Results from logistic regression model indicated increase in risk of neonatal mortality among neonates those born to young mothers aged 13-19 years compared with those whose mother's aged 20-34 years (aOR = 1.64, 95% CI = 1.34-2.02). We also found that neonates in second birth order were more likely to die than those in first birth order (aOR = 1.85: 95% CI = 1.52-2.26). The risk of neonatal mortality among offspring of women who had a partner co-resident was 18% times lower as compared with offspring of mothers without a partner co-resident in the household (aOR = 0.82: 95% CI = 0.66-0.98). Short birth interval (<33 months) was associated with increased risk of neonatal mortality (aOR = 1.50, 95% CI =1.16-1.96) compared with long birth interval (> = 33 months). Male born neonates were found to have an increased risk (aOR = 1.34, 95% CI =1.13- 1.58) of neonatal mortality as compared to their female counterparts.

CONCLUSIONS

Delaying the age at first birth may be a valuable strategy to promote and improve neonatal health and survival. Moreover, birth order, birth interval, mother's partner co-residence and sex of the neonate appeared as important markers for neonatal survival.

Factores asociados con el índice de masa corporal materno en un grupo de gestantes adolescentes, Medellín, Colombia

El estudio tuvo como objetivo evaluar la influencia de factores socioeconómicos, de seguridad alimentaria, de salud, y algunas medidas antropométricas, en la clasificación del índice de masa corporal (IMC) en un grupo de gestantes adolescentes de la ciudad de Medellín, Colombia, durante el tercer trimestre de gestación. Se realizó un estudio analítico observacional transversal con 294 gestantes. Para el análisis se utilizó un análisis bivariado y un modelo de regresión logística. La mayor probabilidad de presentar bajo peso gestacional la tuvieron aquellas gestantes cuyas familias devengaban menos de un salario mínimo (OR = 5,8; IC95%: 1,97-16,8). Ser menor de 15 años aumentó cuatro veces la probabilidad bajo peso gestacional y tener un perímetro del brazo y de pantorrilla por encima de 24cm y 32cm, respectivamente, reduce la probabilidad de presentar bajo peso gestacional en un 94% (perímetro de brazo: OR = 0,1; IC95%: 0,0-0,2); (perímetro de pantorrilla: OR = 0,1; IC95%: 0,0-0,2). Se concluye que los ingresos y la edad cronológica se asociaron con el bajo peso gestacional. Los perímetros de brazo y pantorrilla se correlacionaron de forma positiva con el peso materno.

Stability of parental care across siblings from undisturbed and challenged pregnancies: intrinsic maternal dispositions of female rhesus monkeys

The concept of fetal programming is based on the idea that the developmental trajectory of infants is adjusted in response to in utero conditions. In species with extended parental care, these prenatally derived tendencies are further substantiated by behavioral attributes of the mother during the postnatal period. We investigated the stability of maternal behavioral interactions with infant monkeys and carefully varied prenatal conditions across siblings reared by the same mother. We hypothesized that effects of prenatal disturbance and the infant's susceptibility would be differentially affected by maternal attributes. Using hierarchical linear modeling, we analyzed observational data on 121 rhesus macaques reared by a total of 35 multiparous mothers. A portion of the variance in 5 dyadic behaviors was statistically driven by the infant (or was unique to a particular mother-infant pair), but stable maternal propensities and a consistent style of care across siblings also substantially influenced behavioral interactions. Moreover, the magnitude and direction of the prenatal effects were contingent on a female's intrinsic dispositions. When mothers typically exhibited high levels of a corresponding behavior, responsiveness to infants was enhanced as a consequence of prenatal disturbance. The opposite was true for less expressive females. Challenges to the well-being of pregnancy thus served to accentuate maternal predispositions and served to magnify the range of variation in mother-infant behavior across the whole population.

Early menarche as an alternative reproductive tactic in human females: an evolutionary approach to reproductive health issues

The age at which a female reaches sexual maturity is critical in determining her future reproductive health and success. Thus, a worldwide decline in menarcheal age (timing of first menstrual period) may have serious long-term consequences. Early menarcheal timing (first menstrual period before age 12) can have a negative effect on fecundity, as well as the quality and quantity of offspring, and may consequently influence population growth or decline. In this paper, we apply an evolutionary framework to modern human health, and assess both proximate and ultimate consequences of declining menarcheal age. Examination of human reproductive health within an evolutionary framework is innovative and essential, because it illuminates the ultimate consequences of a declining age of menarche and facilitates new ways of thinking about the long-term and intergenerational transmission of health and disease; thus, an evolutionary framework lends itself to innovative public health and policy programs. In this paper, we examine whether or not early menarche is an alternative reproductive tactic that modern human females employ in response to a stressful environment, and whether or not early menarche is ultimately beneficial.

Maternal programming of reproductive function and behavior in the female rat

Parental investment can be used as a forecast for the environmental conditions in which offspring will develop to adulthood. In the rat, maternal behavior is transmitted to the next generation through epigenetic modifications such as methylation and histone acetylation, resulting in variations in estrogen receptor alpha expression. Natural variations in maternal care also influence the sexual strategy adult females will adopt later in life. Lower levels of maternal care are associated with early onset of puberty as well as increased motivation to mate and greater receptivity toward males during mating. Lower levels of maternal care are also correlated with greater activity of the hypothalamus-pituitary-gonadal axis, responsible for the expression of these behaviors. Contrary to the transition of maternal care, sexual behavior cannot simply be explained by maternal attention, since adoption studies changed the sexual phenotypes of offspring born to low caring mothers but not those from high caring dams. Indeed, mothers showing higher levels of licking/grooming have embryos that are exposed to high testosterone levels during development, and adoption studies suggest that this androgen exposure may protect their offspring from lower levels of maternal care. We propose that in the rat, maternal care and the in utero environment interact to influence the reproductive strategy female offspring display in adulthood and that this favors the species by allowing it to thrive under different environmental conditions.