The effect of birth timing manipulation around carnival on birth indicators in Brazil.

This paper studies the patterns and consequences of birth timing manipulation around the carnival holiday in Brazil. We document how births are displaced around carnival and estimate the effect of displacement on birth indicators. We show that there is extensive birth timing manipulation in the form of both anticipation and postponement that results in a net increase in gestational length and reductions in neonatal and early neonatal mortality, driven by postponed births that would otherwise happen through scheduled c-sections. We also find a reduction in birthweight for high-risk births at the bottom of the weight distribution, driven by anticipation. Therefore, restrictions on usual delivery procedures due to the carnival holiday can be both beneficial and detrimental, raising a double-sided issue to be addressed by policymakers.

The relationship between birth timing, circuit wiring, and physiological response properties of cerebellar granule cells.

Cerebellar granule cells (GrCs) are usually regarded as a uniform cell type that collectively expands the coding space of the cerebellum by integrating diverse combinations of mossy fiber inputs. Accordingly, stable molecularly or physiologically defined GrC subtypes within a single cerebellar region have not been reported. The only known cellular property that distinguishes otherwise homogeneous GrCs is the correspondence between GrC birth timing and the depth of the molecular layer to which their axons project. To determine the role birth timing plays in GrC wiring and function, we developed genetic strategies to access early- and late-born GrCs. We initiated retrograde monosynaptic rabies virus tracing from control (birth timing unrestricted), early-born, and late-born GrCs, revealing the different patterns of mossy fiber input to GrCs in vermis lobule 6 and simplex, as well as to early- and late-born GrCs of vermis lobule 6: sensory and motor nuclei provide more input to early-born GrCs, while basal pontine and cerebellar nuclei provide more input to late-born GrCs. In vivo multidepth two-photon Ca2+ imaging of axons of early- and late-born GrCs revealed representations of diverse task variables and stimuli by both populations, with modest differences in the proportions encoding movement, reward anticipation, and reward consumption. Our results suggest neither organized parallel processing nor completely random organization of mossy fiber→GrC circuitry but instead a moderate influence of birth timing on GrC wiring and encoding. Our imaging data also provide evidence that GrCs can represent generalized responses to aversive stimuli, in addition to recently described reward representations.

Birth timing generates reproductive trade-offs in a non-seasonal breeding primate.

The evolutionary benefits of reproductive seasonality are often measured by a single-fitness component, namely offspring survival. Yet different fitness components may be maximized by different birth timings. This may generate fitness trade-offs that could be critical to understanding variation in reproductive timing across individuals, populations and species. Here, we use long-term demographic and behavioural data from wild chacma baboons (Papio ursinus) living in a seasonal environment to test the adaptive significance of seasonal variation in birth frequencies. We identify two distinct optimal birth timings in the annual cycle, located four-month apart, which maximize offspring survival or minimize maternal interbirth intervals (IBIs), by respectively matching the annual food peak with late or early weaning. Observed births are the most frequent between these optima, supporting an adaptive trade-off between current and future reproduction. Furthermore, infants born closer to the optimal timing favouring maternal IBIs (instead of offspring survival) throw more tantrums, a typical manifestation of mother-offspring conflict. Maternal trade-offs over birth timing, which extend into mother-offspring conflict after birth, may commonly occur in long-lived species where development from birth to independence spans multiple seasons. Our findings therefore open new avenues to understanding the evolution of breeding phenology in long-lived animals, including humans.

Large-scale variation in birth timing and synchrony of a large herbivore along the latitudinal and altitudinal gradients.

Hopkins' Bioclimatic Law predicts geographical patterns in phenological timing by establishing a correspondence between latitudinal and altitudinal gradients. First proposed for key phenological events of plants, such as leaf sprouting or flowering dates, this law has rarely been used to assess the geographical equivalence of key life-history traits of mammals. We hypothesize that (H1) parturition dates of European roe deer Capreolus capreolus are delayed and more synchronized at higher latitudes and altitudes, (H2) parturition timing varies along latitudinal and altitudinal gradients in a way that matches the Hopkins' Bioclimatic Law and (H3) females adjust parturition timing to match the period of high energy demand with peak resource availability. We used parturition dates of 7,444 European roe deer from Switzerland to assess altitudinal variation in birth timing and synchrony from 288 to 2,366 m a.s.l. We then performed a literature survey to compare altitudinal results with those from different populations along the species' latitudinal range of distribution. Finally, we performed spatial analysis combining our highly resolved altitudinal data on parturition dates with plant phenology data. As expected, parturition dates were delayed with increasing latitude and altitude. This delay matched the Bioclimatic Law, as the effect of 1º increase in latitude was similar to 120 m increase in altitude. However, while parturitions were more synchronized with increasing altitude, we did not detect any trend along the latitudinal gradient. Finally, plant phenology explained altitudinal variation in parturition timing better than a linear effect of altitude. Our findings clearly demonstrate the ability of a large herbivore to match parturition timing with phenological conditions across the altitudinal gradient, even at the smallest spatial scales.

Social context of first birth timing in a rapidly changing rural setting.

This article examines the influence of social context on the rate of first birth. Drawing on socialization models, I develop a theoretical framework to explain how different aspects of social context (i.e., neighbors), may affect the rate of first birth. Neighbors, who in the study setting comprise individuals' immediate social context, have an important influence on the rate of first birth. To test my hypotheses, I leverage a setting, measures and analytical techniques designed to study the impact of macro-level social contexts on micro-level individual behavior. The results show that neighbors' age at first birth, travel to the capital city and media exposure tend to reduce the first birth rate, while neighbors' non-family work experience increases first birth rate. These effects are independent of neighborhood characteristics and are robust against several key variations in model specifications.

Influence of interpregnancy interval on neonatal morbidity.

OBJECTIVE: We sought to assess the influence of birth spacing on neonatal morbidity, stratified by gestational age at birth. STUDY DESIGN: This was a population-based retrospective cohort study using Ohio birth records, 2006 through 2011. We compared various interpregnancy interval (IPI) lengths in multiparous mothers with the rate and risk of adverse newborn outcomes. The frequency of neonatal intensive care unit admission or neonatal transport to a tertiary care facility was calculated for births occurring after IPI lengths: <6, 6 to <12, 12 to <24, 24 to <60, and ≥60 months, and stratified by week of gestational age. Neonatal morbidity risk was calculated for each IPI compared to 12 to <24 months (referent), and adjusted for the concomitant influences gestational age at birth, maternal race, age, and prior preterm birth. RESULTS: We analyzed 395,146 birth outcomes of singleton nonanomalous neonates born to multiparous mothers. The frequency and adjusted odds of neonatal morbidity were lowest following IPI of 12 to <24 months (4.1%) compared to short IPIs of <6 months (5.7%; adjusted odds ratio [adjOR], 1.40; 95% confidence interval [CI], 1.32-1.49) and 6 to <12 months (4.7%; adjOR, 1.19; 95% CI, 1.13-1.25), and long IPIs 24 to <60 months (4.6%; adjOR, 1.12; 95% CI, 1.08-1.17) and ≥60 months (5.8%; adjOR, 1.34; 95% CI, 1.28-1.40), despite adjustment for important confounding factors including gestational age at birth. The lowest frequency of adverse neonatal outcomes occurred at 40-41 weeks for all IPI groups. The frequency of other individual immediate newborn morbidities were also increased following short and long IPIs compared to birth following a 12- to <24-month IPI. CONCLUSION: IPI length is a significant contributor to neonatal morbidity, independent of gestational age at birth. Counseling women to plan an optimal amount of time between pregnancies is important for newborn health.

The Effect of Fatherhood on Employment Hours: Variation by Birth Timing, Marriage and Coresidence.

Drawing on the life course paradigm, I assess how the effect of fatherhood on employment hours varies by age of becoming a parent and time elapsed since the birth. Using the National Longitudinal Survey of Youth - 1979 Cohort from 1979 to 2002 (N = 28,514 observations), separate effects are estimated based on fathers' marital status and co-residence with own children. Only unmarried men who became fathers before 24 work longer hours immediately after a first birth, but in the long run, most early fathers work fewer hours as a result of parenthood. Over time, unmarried but coresident men who became fathers between 24 and 29 increase their hours, as do married, coresident men who delayed fatherhood until 30 or older. However, the latter increase is moderated by support for egalitarian gender roles. The findings shed light on the contemporary transition to adulthood and on men's work-family balance.

Western lowland gorilla (Gorilla gorilla gorilla) birth patterns and human presence in zoological settings.

There is some evidence to suggest that zoo visitors may have a disruptive impact on zoo-housed animals, especially primates. While some consider western lowland gorillas (Gorilla gorilla gorilla) to be particularly reactive to large crowds, the evidence of these effects is mixed, and is likely highly influenced by exhibit design, and group composition. While the majority of studies have focused on behavioral responses to human presence, there is the potential for physiological effects as well, including the possibility of affecting the timing of parturition. Such effects have been demonstrated in laboratory-housed callitrichids and chimpanzees, but unlike laboratory settings where human presence is lowest during the weekends, human presence might peak during weekends in public zoo settings. However, in a study of zoo-housed chimpanzees, there were no significant differences between the number of chimpanzee births that occurred on weekdays compared to weekends [Wagner and Ross, 2008], and we sought to test these questions with gorillas. We analyzed the timing of 336 live gorilla births and 48 stillbirths at 53 accredited North American zoos from 1985-2014, and similarly to chimpanzees, found no weekend or weekday effect on number of births (live births: G = 0.000, p = 1; stillbirths: G = 0.166, p < 0.684). These data add to our understanding of the potential influence of human presence on primate behavior and physiology, and add to evidence suggesting that the effects of zoo visitors on exhibited species may be less profound than previously assumed.

Phenomenal advanced age of pupping in a captive Pacific harbor seal (Phoca vitulina richardsi).

To better define the life history in the captive environment, we describe the reproductive history and advanced age of pupping of a female Pacific harbor seal (Phoca vitulina richardsi) at the Henry Vilas Zoo (HVZ) in Madison, Wisconsin. This female gave birth to a viable pup on May 16, 2012, at the age of 42 years and is the oldest documented birth reported for this species. This female also demonstrated high temporal fidelity to her previously described birth timing. The pup's sire was also 42 years at the time of birth. Captive harbor seals can remain reproductively healthy into their 5th decade.

Influence of interpregnancy interval on birth timing.

OBJECTIVE: To assess the influence of inadequate birth spacing on birth timing distribution across gestation. DESIGN: Population-based retrospective cohort study using vital statistics birth records. SETTING: Ohio, USA. STUDY POPULATION: Singleton, non-anomalous live births ≥20 weeks to multiparous mothers, 2006-2011. METHODS: Birth frequency at each gestational week was compared following short IPIs of <6, 6-12 and 12-18 months versus referent group, normal IPI≥18 months. MAIN OUTCOME MEASURES: Frequency of birth at each gestational week; preterm <37 weeks; <39 and ≥40 weeks. RESULTS: Of 454,716 births, 87% followed a normal IPI≥18 months, 10.7% had IPI 12-18 months and 2.2% with IPI<12 months. The risk of delivery<39 weeks was higher following short IPI<12 months, adj OR (odds ratio) 2.78 (95% CI 2.64, 2.93). 53.3% of women delivered before the 39th week after IPI<12 months compared with 37.5% of women with normal IPI, P<0.001. Likewise, birth at ≥40 weeks was decreased (16.9%) following short IPI<12 months compared to normal IPI, 23.2%, adj OR 0.67 (95% CI 0.64, 0.71). This resulted in a shift of the frequency distribution curve of birth by week of gestation to the left for pregnancies following a short IPI<12 months and 12-18 months compared to, birth spacing≥18 months. CONCLUSIONS: While short IPI is a known risk factor for preterm birth, our data show that inadequate birth spacing is associated with decreased gestational age for all births. Pregnancies following short IPIs have a higher frequency of birth at all weeks of gestation prior to 39 and fewer births≥40 weeks, resulting in overall shortened pregnancy duration.

Birth timing and the mother-infant relationship predict variation in infant behavior and physiology.

The current study explored whether birth timing, known to influence the mother-infant relationship, also affected infant physiology up to 9 months later and infant behavior at weaning. Infant blood samples were collected at 5.75 and 8.75 months of age to assess functioning of the hypothalamic-pituitary-adrenal axis as well as the antibody response to a Cholera vaccination. Path analysis indicated infants born late in the birth season had less Relaxed relationships with their mothers. A less-Relaxed relationship was associated with greater infant Positive Engagement and Distress, which were negatively correlated, suggesting infants may have different strategies of coping with this type of relationship. Low Relaxed scores were also associated with higher infant cortisol concentrations at 5.75 months, which was associated with a reduced immune response to a vaccination 3 months later. Together these results indicate that the influence of birth timing on the mother-infant relationship may have consequences for infant development.

Birth timing and behavioral responsiveness predict individual differences in the mother-infant relationship and infant behavior during weaning and maternal breeding.

There is a great deal of variability in mother-infant interactions and infant behavior across the first year of life in rhesus monkeys. The current article has two specific aims: (1) to determine if birth timing predicts variability in the mother-infant relationship and infant behavior during weaning and maternal breeding, and (2) to identify predictors of infant behavior during a period of acute challenge, maternal breeding. Forty-one mother-infant pairs were observed during weaning when infants were 4.5 months old, and 33 were followed through maternal breeding. Subjective ratings of 16 adjectives reflecting qualities of maternal attitude, mother-infant interactions, and infant attitude were factor analyzed to construct factors relating to the mother-infant relationship (Relaxed and Aggressive) and infant behavior (Positive Engagement and Distress). During weaning, late born infants were more Positively Engaged than peak born infants (ANOVA, P < 0.05); however, birth timing did not affect the mother-infant relationship factors Relaxed and Aggressive or the infant attitude factor Distress. During maternal breeding, early born infants had less Relaxed relationships with their mothers than peak or late born infants, higher Positive Engagement scores than peak or late born infants, and tended to have higher Distress scores than peak born infants (repeated-measures ANOVA, P < 0.05). In addition, Distress scores were higher during maternal breeding than during the pre- and postbreeding phases. Finally, multiple regression (P < 0.05) indicated that while infant behavioral responsiveness predicted infant Positive Engagement during the acute challenge of maternal breeding, qualities of the mother-infant relationship predicted infant Distress. These data suggest that birth timing influences the patterns of mother-infant interactions during weaning and maternal breeding. Additionally, infant behavioral responsiveness and mother-infant relationship quality impact infant social engagement and affect expression, respectively.

The birth hour of mammals: insights from intra-specific variation in wild blue monkeys.

While most mammals show birth hour peaks at times of the 24-h cycle when they are less active, there are exceptions to this general pattern. Such exceptions have been little explored, but may clarify evolutionary reasons for the diel timing of births. We investigated intraspecific variation in birth hour in wild blue monkeys Cercopithecus mitis stuhlmanni, a diurnal primate, to identify factors that differentiated daytime versus nighttime births. Behavioral and life history data from 14 groups over 14 years revealed that 4% of 484 births occurred during the day. Probability of daytime birth varied with mother's age, peaking at 15.7 years. Births whose annual timing deviated most from the population's peak birth months were 5 times more likely to occur during daytime than those that deviated less. There was no evidence that mother's rank or infant sex influenced birth hour, and mixed evidence that daytime births were more probable in larger groups. Survivorship did not differ significantly for infants born during the day versus night. Prime-aged mothers may be able to handle the consequences of an unusual birth hour more successfully than mothers with less experience or those weakened by age. Daytime birth may be more advantageous in the off-season because nights are colder at that time of year. These findings are consistent with hypotheses relating birth hour to the risk of losing social protection in group-living animals, but are not consistent with those emphasizing risk of conspecific harassment. Patterns of within-species variation can help in evaluating evolutionary hypotheses for non-random birth hour.

Changing physicians' incentives to control the C-section rate: Evidence from a major health care reform in Iran.

We evaluate the effect of a major health care policy in public hospitals which changed the demand and supply side incentives for c-section procedures in 2014 in Iran, where the c-section rate at the time was 55%. Following the reform, vaginal delivery became free for patients. The policy also introduced financial incentives to doctors for performing vaginal deliveries and set a cap on their maximum c-section rate. We show that supply side incentives had a major role in the effectiveness of the programme, after which the national rate reduced by 6 percentage points. This reduction was mainly driven by first-birth mothers. The reform also shifted doctors with high c-section rates out of public hospitals. We cannot find any adverse effect on Apgar score, hospitalisation or mortality; however, gestation length and birth weight significantly increased.

Migration distance and maternal resource allocation determine timing of birth in a large herbivore.

Birth timing is a key life-history characteristic that influences fitness and population performance. For migratory animals, however, appropriately timing birth on one seasonal range may be constrained by events occurring during other parts of the migratory cycle. We investigated how the use of capital and income resources may facilitate flexibility in reproductive phenology of migratory mule deer in western Wyoming, USA, over a 5-yr period (2015-2019). Specifically, we examined how seasonal interactions affected three interrelated life-history characteristics: fetal development, birth mass, and birth timing. Females in good nutritional condition at the onset of winter and those that migrated short distances had more developed fetuses (measured as fetal eye diameter in March). Variation in parturition date was explained largely by fetal development; however, there were up to 16 d of plasticity in expected birth date. Plasticity in expected birth date was shaped by income resources in the form of exposure to spring green-up. Although individuals that experienced greater exposure to spring green-up were able to advance expected birth date, being born early or late with respect to fetal development had no effect on birth mass of offspring. Furthermore, we investigated the trade-offs migrating mule deer face by evaluating support for existing theory that predicts that births should be matched to local peaks in resource availability at the birth site. In contrast to this prediction, only long-distance migrants that paced migration with the flush of spring green-up, giving birth shortly after ending migration, were able to match birth with spring green-up. Shorter-distance migrants completed migration sooner and gave birth earlier, seemingly trading off more time for offspring to grow and develop over greater access to resources. Thus, movement tactic had profound downstream effects on birth timing. These findings highlight a need to reconsider classical theory on optimal birth timing, which has focused solely on conditions at the birth site.

Changing the light schedule in late pregnancy alters birth timing in mice.

In rats, birth timing is affected by changes in the light schedule until the middle of the pregnancy period. This phenomenon can be used to control birth timing in the animal industry and/or clinical fields. However, changes in the light schedule until the middle of the pregnancy period can damage the fetus by affecting the development of the major organs. Thus, we compared birth timing in mice kept under a 12-h light/12-h darkness schedule (L/D) throughout pregnancy with that of mice kept under a light schedule that changed from L/D to constant light (L/L) or constant darkness (D/D) from day 17.5 of pregnancy, the latter phase of the pregnancy period. On average, the pregnancy period was longer in D/D mice (19.9 days) than L/L or L/D mice (19.5 and 19.3 days, respectively, P < 0.05), confirming that light schedule affects birth timing. The average number of newborns was the same in L/L, L/D, and D/D mice (7.5, 7.8, and 7.9, respectively), but the average newborn weight of L/L mice (1.3 g) was lower than that of L/D and D/D mice (both 1.4 g, P < 0.05), indicating that constant light has detrimental effects on fetus growth. However, the percentage of dead newborns was the same between L/L, L/D, and D/D mice (11.1, 10.6, and 3.6%, respectively). The serum progesterone level on day 18.5 of pregnancy in L/D mice was 42.8 ng/ml, lower (P < 0.05) than that of D/D mice (65.3 ng/ml), suggesting that light schedule affects luteolysis. The average pregnancy period of mice lacking a circadian clock kept under D/D conditions from day 17.5 of pregnancy (KO D/D) (20.3 days) was delayed compared with wild-type (WT) D/D mice (P < 0.05). However, the average number of newborns, percentage of births with dead pups, and weight per newborn of KO D/D mice (7.6, 3.6%, and 1.4 g, respectively) were the same as WT mice kept under D/D conditions. A direct effect of the circadian clock on the mechanism(s) regulating birth timing was questionable, as the lighter average weight per KO fetus (0.6 g) versus WT fetus (0.7 g) on day 17.5 of pregnancy might have caused the delay in birth. The range of birth timing in KO D/D mice was the same as that of WT D/D mice, indicating that the circadian clock does not concentrate births at one time.

Does Birth Trigger Cell Death in the Developing Brain?

Developmental cell death eliminates half of the neurons initially generated in the mammalian brain, and occurs perinatally in many species. It is possible that the timing of neuronal cell death is developmentally programmed, and only coincidentally associated with birth. Alternatively, birth may play a role in shaping cell death. To test these competing hypotheses, we experimentally advanced or delayed birth by 1 d in mice (within the normal range of gestation for the species) and examined effects on the temporal pattern and magnitude (amount) of neuronal cell death, using immunohistochemical detection of activated caspase-3 as a cell death marker. In order to detect effects of subtle changes in birth timing, we focused on brain areas that exhibit sharp postnatal peaks in cell death. We find that advancing birth advances peak cell death, supporting the hypothesis that birth triggers cell death. However, a delay of birth does not delay cell death. Thus, birth can advance cell death, but if postponed, a developmental program governs. Advancing or delaying birth also caused region-specific changes in the overall magnitude of cell death. Our findings shed light on the long-standing question of what controls the timing and magnitude of developmental neuronal cell death, and position birth as an orchestrator of brain development. Because humans across the world now routinely alter birth timing, these findings may have implications for current obstetric practices.

Adolescent Fertility Attitudes and Childbearing in Early Adulthood.

Teens' attitudes about adolescent childbearing predict childbearing in the short term. If these attitudes reflect persistent goals and values, they may also be linked to later outcomes. To test long-term linkages, we analyze the association of adolescent fertility attitudes with actual and prospective fertility in adulthood using Waves I (1994-95) and IV (2007-08) of the National Longitudinal Study of Adolescent to Adult Health and focusing on men (N = 4,275) and women (N=4,418) without a teen birth. For women, we find that more negative teen attitudes predict lower hazards of a first birth up to around age 30 but that teens' attitudes are unrelated to planned childlessness among those who have not yet had children. Men's adolescent attitudes are unrelated to actual fertility or prospective intentions. For both men and women, more advantaged individuals are less likely to have had a child by around age 30; socioeconomic advantage is also related to postponement of childbearing rather than planned childlessness, though more so for women than men. We interpret the findings as evidence that, for girls, teens' attitudes toward adolescent childbearing capture an internalization of social schema about childbearing, childrearing, and sequencing with other life outcomes but do not reflect overall preferences about having children. More work is needed to understand the psychosocial factors that influence men's fertility.

Race Differences in Linking Family Formation Transitions to Women's Mortality.

We examine how the timing and sequencing of first marriage and childbirth are related to mortality for a cohort of 4,988 white and black women born between 1922 and 1937 from the National Longitudinal Survey of Mature Women. We use Cox proportional hazard models to estimate race differences in the association between family formation transitions and mortality. Although we find no relationships between marital histories and longevity, we do find that having children, the timing of first birth, and the sequencing of childbirth and marriage are associated with mortality. White women who had children lived longer than those who had none, but the opposite was found for black women. The effects of birth timing also differed by race; delaying first birth to older ages was protective for white women but not black women. These results underscore the importance of social context in the study of life course transitions.

Birth dates vary with fixed and dynamic maternal features, offspring sex, and extreme climatic events in a high-latitude marine mammal.

Reproductive synchrony tends to be widespread in diverse species of plants and animals, especially at higher latitudes. However, for long-lived mammals, birth dates for different individuals can vary by weeks within a population. A mother's birth timing can reveal useful information about her reproductive abilities and have important implications for the characteristics and survival of her offspring. Despite this, our current knowledge of factors associated with variation in birth dates is modest. We used long-term data for known-age Weddell seals in Antarctica and a Bayesian hierarchical modeling approach to study how birth dates varied with fixed and temporally varying features of mothers, whether sex allocation varied with birth timing, and annual variation in birth dates. Based on birth dates for 4465 pups born to 1117 mothers aged 4-31, we found that diverse features of mothers were associated with variation in birth dates. Maternal identity was the most important among these. Unlike most studies, which have reported that birth dates occur earlier as mothers age, we found that birth dates progressively occurred earlier in the year in the early part of a mother's reproductive life, reached a minimum at age 16, and then occurred later at later ages. Birth dates were positively related to a mother's age at primiparity and recent reproductive effort. The earliest birth dates were for pups born to prime-age mothers who did not reproduce in the previous year but began reproduction early in life, suggesting that females in the best condition gave birth earlier than others. If so, our finding that male pups tended to be born earlier than females provides support for the Trivers-Willard sex-allocation model. Average birth dates were quite consistent across years, except for 2 years that had notable delays and occurred during the period when massive icebergs were present and disrupted the ecosystem.