Birthweight and paternal involvement predict early reproduction in British women: evidence from the National Child Development Study

There is considerable interest in the mechanisms maintaining early reproduction in the most socioeconomically disadvantaged groups in developed countries. Previous research has suggested that differential exposure to early-life factors such as low birthweight and lack of paternal involvement during childhood may be relevant. Here, we used longitudinal data on the female cohort members from the UK National Child Development Study (n=3014-4482 depending upon variables analysed) to investigate predictors of early reproduction. Our main outcome measures were having a child by age 20, and stating at age 16 an intended age of reproduction of 20 years or lower. Low paternal involvement during childhood was associated with increased likelihood of early reproduction (O.R. 1.79-2.25) and increased likelihood of early intended reproduction (O.R. 1.38-2.50). Low birthweight for gestational age also increased the odds of early reproduction (O.R. for each additional s.d. 0.88) and early intended reproduction (O.R. for each additional s.d. 0.81). Intended early reproduction strongly predicted actual early reproduction (O.R. 5.39, 95% CI 3.71-7.83). The results suggest that early-life factors such as low birthweight for gestational age, and low paternal involvement during childhood, may affect women?s reproductive development, leading to earlier target and achieved ages for reproduction. Differential exposure to these factors may be part of the reason that early fertility persists in socioeconomically disadvantaged groups. We discuss our results with respect to the kinds of interventions likely to affect the rate of teen pregnancy

Patterns of physical and psychological development in future teenage mothers

Background and objectives: Teenage childbearing may have childhood origins and can be viewed as the outcome of a coherent reproductive strategy associated with early environmental conditions. Life-history theory would predict that where futures are uncertain fitness can be maximized through diverting effort from somatic development into reproduction. Even before the childbearing years, future teenage mothers differ from their peers both physically and psychologically, indicating early calibration to key ecological factors. Cohort data has not been deliberately collected to test life-history hypotheses within Western populations. None the less, existing data sets can be used to pursue relevant patterns using socioeconomic variables as indices of relevant ecologies. Methodology: We examined the physical and psychological development of 599 young women from the National Child Development Study who became mothers before age 20, compared to 599 socioeconomically matched controls. Results: Future young mothers were lighter than controls at birth and shorter at age 7. They had earlier menarche and accelerated breast development, earlier cessation of growth, and shorter adult stature. Future young mothers had poorer emotional and behavioural adjustment than controls at age 7 and especially 11, and by age 16, idealised younger ages for marriage and parenthood than did the controls. Conclusions and implications: The developmental patterns we observed are consistent with the idea that early childbearing is a component of an accelerated reproductive strategy that is induced by early-life conditions. We discuss the implications for the kinds of interventions likely to affect the rate of teenage childbearing

The role of placental kisspeptin in trophoblast invasion and migration: An assessment in Kiss1r knockout mice, BeWo cell lines and human term placenta

Context: There is mounting evidence implicating kisspeptin signalling in placental development and function. Aims: This study aimed to elucidate kisspeptin\u27s role in trophoblast invasion and migration using three experimental models. Methods: First, we examined the mouse fetus and placenta in a kisspeptin receptor (Kiss1r) knockout (KO) model. Fetal/placental weights and gene expression (quantitative polymerase chain reaction) were assessed. Second, we determined kisspeptin effects on a human trophoblast (BeWo) cell line in vitro. Third, we examined KISS1 and KISS1R gene expression in human placenta from term and pre-Term pregnancies. Key results: No difference was found in fetal or placental weight between Kiss1r KO and wildtype mice. However, expression of the trophoblast invasion marker, Mmp2 mRNA, was greater in the placental labyrinth zone of Kiss1r KO mice. BeWo cell models of villus cytotrophoblast and syncytiotrophoblast cells exhibited kisspeptin protein expression, with greater expression in syncytiotrophoblast, consistent with KISS1 mRNA. Kisspeptin treatment inhibited the migratory potential of cytotrophoblast-like cells. Finally, while no difference was seen in KISS1 and KISS1R mRNA between term and pre-Term placentas, we saw a difference in the relative expression of each gene pre-Term. We also observed a positive correlation between KISS1 expression and maternal body mass index. Conclusions: Our results indicate that kisspeptin may inhibit trophoblast invasion. Implications: Further investigation is required to clarify specific regulatory mechanisms

Increased Mortality Exposure within the Family Rather than Individual Mortality Experiences Triggers Faster Life-History Strategies in Historic Human Populations

Life History Theory predicts that extrinsic mortality risk is one of the most important factors shaping (human) life histories. Evidence from contemporary populations suggests that individuals confronted with high mortality environments show characteristic traits of fast life-history strategies: they marry and reproduce earlier, have shorter birth intervals and invest less in their offspring. However, little is known of the impact of mortality experiences on the speed of life histories in historical human populations with generally higher mortality risk, and on male life histories in particular. Furthermore, it remains unknown whether individual-level mortality experiences within the family have a greater effect on life-history decisions or family membership explains life-history variation. In a comparative approach using event history analyses, we study the impact of family versus individual-level effects of mortality exposure on two central life-history parameters, ages at first marriage and first birth, in three historical human populations (Germany, Finland, Canada). Mortality experience is measured as the confrontation with sibling deaths within the natal family up to an individual's age of 15. Results show that the speed of life histories is not adjusted according to individual-level mortality experiences but is due to family-level effects. The general finding of lower ages at marriage/reproduction after exposure to higher mortality in the family holds for both females and males. This study provides evidence for the importance of the family environment for reproductive timing while individual-level mortality experiences seem to play only a minor role in reproductive life history decisions in humans

Maternal Psychosocial Stress during Pregnancy and Placenta Weight: Evidence from a National Cohort Study

To study in a large-scale cohort with prospective data the associations between psychosocial stress during pregnancy and placenta weight at birth. Animal data suggest that the placenta is involved in stress-related fetal programming.; We defined a priori two types of psychosocial stress during pregnancy, life stress (perceived burdens in major areas of life) and emotional symptoms (e.g. anxiety). We estimated the associations of maternal stress during pregnancy with placenta weight at birth, controlled for length of gestation, by predicting gestational age- and sex-specific z-scores of placenta weight through multiple regression analysis, adjusted for potential confounders (N?=?78,017 singleton pregnancies). Life stress (per increase in stress score by 1, range: 0-18) during pregnancy was associated with increased placenta weight at birth (z-score, reported in 10(-3); B, 14.33; CI, 10.12-18.54). In contrast, emotional symptoms during pregnancy were not associated with placenta weight at birth.; Maternal life stress but not emotional symptoms during pregnancy was associated with increased placenta weight at birth; yet, the association-estimate was rather small. Our results may contribute to a better understanding of the role of the placenta in the regulation of intrauterine processes in response to maternal stress

Sex Ratio at Birth and Mortality Rates Are Negatively Related in Humans

Evolutionary theory posits that resource availability and parental investment ability could signal offspring sex selection, in order to maximize reproductive returns. Non-human studies have provided evidence for this phenomenon, and maternal condition around the time of conception has been identified as most important factor that influence offspring sex selection. However, studies on humans have reported inconsistent results, mostly due to use of disparate measures as indicators of maternal condition. In the present study, the cross-cultural differences in human natal sex ratio were analyzed with respect to indirect measures of condition namely, life expectancy and mortality rate. Multiple regression modeling suggested that mortality rates have distinct predictive power independent of cross-cultural differences in fertility, wealth and latitude that were earlier shown to predict sex ratio at birth. These findings suggest that sex ratio variation in humans may relate to differences in parental and environmental conditions

Maternal Programming of Sexual Behavior and Hypothalamic-Pituitary-Gonadal Function in the Female Rat

Variations in parental care predict the age of puberty, sexual activity in adolescence and the age at first pregnancy in humans. These findings parallel descriptions of maternal effects on phenotypic variation in reproductive function in other species. Despite the prevalence of such reports, little is known about potential biological mechanisms and this especially true for effects on female reproductive development. We examined the hypothesis that parental care might alter hypothalamic-pituitary-ovarian function and thus reproductive function in the female offspring of rat mothers that vary pup licking/grooming (LG) over the first week postpartum. As adults, the female offspring of Low LG mothers showed 1) increased sexual receptivity; 2) increased plasma levels of luteinizing hormone (LH) and progesterone at proestrus; 3) an increased positive-feedback effect of estradiol on both plasma LH levels and gonadotropin releasing-hormone (GnRH) expression in the medial preoptic region; and 4) increased estrogen receptor α (ERα) expression in the anterioventral paraventricular nucleus, a system that regulates GnRH. The results of a cross-fostering study provide evidence for a direct effect of postnatal maternal care as well as a possible prenatal influence. Indeed, we found evidence for increased fetal testosterone levels at embryonic day 20 in the female fetuses of High compared to Low LG mothers. Finally, the female offspring of Low LG mothers showed accelerated puberty compared to those of High LG mothers. These data suggest maternal effects in the rat on the development of neuroendocrine systems that regulate female sexual behaviour. Together with studies revealing a maternal effect on the maternal behavior of the female offspring, these findings suggest that maternal care can program alternative reproductive phenotypes in the rat through regionally-specific effects on ERα expression

Early-life conditions and age at first pregnancy in British women

There is growing evidence that the reproductive schedules of female mammals can be affected by conditions experienced during early development, with low parental investment leading to accelerated life-history strategies in the offspring. In humans, the relationships between early-life conditions and timing of puberty are well studied, but much less attention has been paid to reproductive behaviour. Here, we investigate associations between early-life conditions and age at first pregnancy (AFP) in a large, longitudinally studied cohort of British women (n = 4553). Low birthweight for gestational age, short duration of breastfeeding, separation from mother in childhood, frequent family residential moves and lack of paternal involvement are all independently associated with earlier first pregnancy. Apart from that of birthweight, the effects are robust to adjustment for family socioeconomic position (SEP) and the cohort member's mother's age at her birth. The association between childhood SEP and AFP is partially mediated by early-life conditions, and the association between early-life conditions and AFP is partially mediated by emotional and behavioural problems in childhood. The overall relationship between early-life adversities and AFP appears to be approximately additive