Birth Patterns Research Articles

Seasonal Variations in Birth Patterns in Greece: A Comprehensive Analysis of National Data From 1956 to 2022.

The seasonality of human births has been studied globally for over two centuries, revealing diverse patterns across populations shaped by intricate interactions involving both biological and socio-cultural factors. This study offers a thorough examination of national birth data in Greece spanning from 1956 to 2022, aiming to elucidate long-term trends and changes in seasonal birth patterns. Data on live births in Greece were categorized by month based on national registries, and the analysis of birth seasonality was conducted annually. The Edwards method was utilized to evaluate birth seasonality by calculating the peak angle (PA), which identifies the center of the seasonal birth distribution. Additionally, the peak-to-low ratio (PLR) was computed for each year to serve as an indicator of the amplitude of birth seasonality. To investigate trends and temporal changes, joinpoint regression analysis was employed, specifically focusing on the annual percentage change (APC) within defined segments, along with a 95% confidence interval (95% CI). A total of 8,144,465 live births were recorded between 1956 and 2022. Birth seasonality was statistically significant for all examined years. The results revealed a progressive shift in the concentration of births to the second half of the year, transitioning from a peak in January and February to two significant major peaks in July and September. Additionally, in the last two decades, the lowest birth rates were observed in spring, particularly in April, as well as in December. The PA shifted significantly over time, moving from mid-January in 1956 to late August in 2022, with an APC of 39.6 (95% CI: 17.4 to 99.7) during 1956-1960 and 7.5 (95% CI: 2.2 to 11.3) during 1960-1975. Between 1975 and 2022, the trend continued at a lower stable rate (APC = 1.0, 95% CI: 0.2 to 1.5). The PLR, after a brief upward trend during 1956-1960 (APC = 6.0, 95% CI: 3.1 to 11.3), exhibited a statistically significant decline in seasonal amplitude from 1960 to 1992 (1960-1964: APC = -5.5, 95% CI: -8.6 to -2.4, 1964-1992: APC = -0.4, 95% CI: -0.8 to -0.2), and relatively stabilized during the last thirty years (1992-2022). This study highlights significant changes in birth seasonality in Greece, marked by a shift in the distribution of births toward the second half of the year and a transition from peaks in births during January and February to two major surges in July and September. These trends reflect evolving reproductive behaviors in the Greek population and hold important implications for reproductive and perinatal healthcare in the country.

Using serosurveys to optimize surveillance for zoonotic pathogens.

Zoonotic pathogens pose a significant risk to human health, with spillover into human populations contributing to chronic disease, sporadic epidemics, and occasional pandemics. Despite the widely recognized burden of zoonotic spillover, our ability to identify which animal populations serve as primary reservoirs for these pathogens remains incomplete. This challenge is compounded when prevalence reaches detectable levels only at specific times of year. In these cases, statistical models designed to predict the timing of peak prevalence could guide field sampling for active infections. Thus, we develop a general model that leverages routinely collected serosurveillance data to optimize sampling for elusive pathogens by predicting time windows of peak prevalence. Using simulated data sets, we show that our methodology reliably identifies times when pathogen prevalence is expected to peak. Then, we demonstrate an implementation of our method using publicly available data from two putative Ebolavirus reservoirs, straw-colored fruit bats (Eidolon helvum) and hammer-headed bats (Hypsignathus monstrosus). We envision our method being used to guide the planning of field sampling to maximize the probability of detecting active infections, and in cases when longitudinal data is available, our method can also yield predictions for the times of year that are most likely to produce future spillover events. The generality and simplicity of our methodology make it broadly applicable to a wide range of putative reservoir species where seasonal patterns of birth lead to predictable, but potentially short-lived, pulses of pathogen prevalence.

Neonatal Mortality Disparities by Gestational Age in European Countries

There are wide disparities in neonatal mortality rates (NMRs, deaths <28 days of life after live birth per 1000 live births) between countries in Europe, indicating potential for improvement. Comparing country-specific patterns of births and deaths with countries with low mortality rates can facilitate the development of effective intervention strategies. To investigate how these disparities are associated with the distribution of gestational age (GA) and GA-specific mortality rates. This was a cross-sectional study of all live births in 14 participating European countries using routine data compiled by the Euro-Peristat Network. Live births with a GA of 22 weeks or higher from 2015 to 2020 were included. Data were analyzed from May to October 2023. GA at birth. The study investigated excess neonatal mortality, defined as a rate difference relative to the pooled rate in the 3 countries with the lowest NMRs (Norway, Sweden, and Finland; hereafter termed the top 3). The Kitagawa method was used to divide this excess into the proportion explained by the GA distribution of births and by GA-specific mortality rates. A sensitivity analysis was conducted among births 24 weeks' GA or greater. There were 35 094 neonatal deaths among 15 123 428 live births for an overall NMR of 2.32 per 1000. The pooled NMR in the top 3 was 1.44 per 1000 (1937 of 1 342 528). Excess neonatal mortality compared with the top 3 ranged from 0.17 per 1000 in the Czech Republic to 1.82 per 1000 in Romania. Excess deaths were predominantly concentrated among births less than 28 weeks' GA (57.6% overall). Full-term births represented 22.7% of the excess deaths in Belgium, 17.8% in France, 40.6% in Romania and 17.3% in the United Kingdom. Heterogeneous patterns were observed when partitioning excess mortality into the proportion associated with the GA distribution vs GA-specific mortality. For example, these proportions were 9.2% and 90.8% in France, 58.4% and 41.6% in the United Kingdom, and 92.9% and 7.1% in Austria, respectively. These associations remained stable after removing births under 24 weeks' GA in most, but not all, countries. This cohort study of 14 European countries found wide NMR disparities with varying patterns by GA. This knowledge is important for developing effective strategies to reduce neonatal mortality.

Birth Patterns in the Aftermath of the 1918 Influenza Pandemic in India: The Case of Madras City.

This paper examines the timing of one-time fluctuations in births subsequent to the 1918 influenza pandemic in Madras (now Chennai), India. After seasonally decomposing key demographic aggregates, we identified abrupt one-time fluctuations in excess births, deaths, and infant deaths. We found a contemporaneous spike in excess deaths and infant deaths and a 40-week lag between the spike in deaths and a subsequent deficit in births. The results suggest that India experienced the same kind of short-term postpandemic "baby bust" that was observed in the United States and other countries. Identifying the mechanisms underlying this widespread phenomenon remains an open question and an important topic for future research.

Racialized inequities in live birth after cancer: A population-based study of 63,000 female adolescents and young adults with cancer.

Fertility after cancer is a top concern for adolescents and young adults with cancer (AYAs) (15-39 years old at diagnosis). The authors characterized live births after cancer by race and ethnicity ("race/ethnicity") in a population-based sample of female AYAs. This study used Texas Cancer Registry data linked to birth certificates (1995-2016) to estimate cumulative incidence of live birth, based on first live birth after cancer, and compared differences by race/ethnicity. Proportional subdistribution hazards models were used to estimate associations between race/ethnicity and live birth, adjusted for diagnosis age, cancer type, stage, year, and prior live birth, overall and for each cancer type. Among 65,804 AYAs, 10-year cumulative incidence of live birth was lower among non-Hispanic Black AYAs than other racial/ethnic groups: 10.2% (95% confidence interval [CI], 9.4-10.9) compared to 15.9% (95% CI, 14.1-17.9) among Asian or Pacific Islander, 14.7% (95% CI, 14.2-15.3) among Hispanic, and 15.2% (95% CI, 14.8-15.6) among non-Hispanic White AYAs (p<.01). In the adjusted overall model, Black AYAs were less likely to have a live birth after cancer than all other groups. In adjusted models for each cancer type, live birth was significantly less likely for Black AYAs with gynecologic cancers or lymphomas (compared to White AYAs) or thyroid cancers (compared to Hispanic AYAs). Black AYAs are less likely than AYAs of other races/ethnicities to have a live birth after cancer, in contrast to patterns of live birth in the general population. Research and action to promote childbearing equity after cancer are imperative.

Colostrum Supplementation to Rescue Antibiotic-Induced Dysbiosis and Reduce Long-Term Obesity Risk

The prevalence of metabolic disease in the United States has increased from 30.4% to 41.9% in the past decades, with rising rates among children. Emerging evidence implicates intestinal microbiome function as contributing to metabolic disease risk, with dysbiosis being associated with overweight and obese status. While sometimes lifesaving, antibioticssuch as azithromycin cause microbiota ecological instability and are significantly associated with a greater risk ofmetabolic disease and obesity in children. Since antibiotics are often necessary, the identification of nutritional interventions to restore microbial membership and function has a high potential value for millions of patients. Colostrum is the first milk produced by mammals immediately after birth and shapes intestinal colonization patterns, specifically enriching Bifidobacterium, Lactobacillus, and limiting the colonization of Proteobacteria. Bovine colostrum containsimmunomodulators, lactoferrin, oligosaccharides, bioactive compounds, and macronutrients. The compounds are similar across mammalian species. Considering the impact of colostrum in the sterile early-life gut, we hypothesized that bovine colostrum provided as a supplemental nutraceutical therapy would augment gut microbial recolonization following antibiotic exposures and mitigate long-term metabolic consequences. Specific pathogen-free (SPF) C57BL/6 mice (male, three weeks old, Jackson Laboratory) were housed under standard laboratory conditions with a 45% high-fat diet. Tylosintartrate antibiotic (ABX) was administered to some mice in drinking water 3 days/week over three weeks, with four days washout/week. To examine colostrum, some animals were provided colostrum gavage during or immediately following ABX exposures. After intervention, body composition and metabolic phenotypes were monitored for 16 weeks.Compared with ABX alone, colostrum following ABX maintained similar body composition and glucose tolerance as controls, while colostrum during ABX appeared similar to ABX alone. Examination of the gut microbiome showed unique enrichment of Akkermansia and Sutterella with decreased Enterobacteriaceae in mice treated with ABX followed by colostrum. Analysis of the gut mucosa demonstrated ABX decreased goblet cell numbers per villi (7.2/villus) compared with control (9.8/villus), and colostrum following ABX elevated goblet cells (8.6/villus). These data suggest colostrum may stimulate epithelial responses that foster host-microbial symbiosis at the mucosal surface and play a role in intestinal recolonization to benefit long-term homeostasis. Dairy Innovation Hub, UW-Madison. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Spillover effect of government relocations on economic growth in Chinese cities

This paper investigates the spillover effect of government locations on economic growth by exploring more than 180 relocation events of city governments in China. Empirical results demonstrate that government relocations improve regional economic growth measured by night lights. This positive effect decreases with the distance to city governments’ new locations. Government relocations are also found to accelerate urbanization. Potential mechanisms include the changes in land conversion and firm birth patterns in the move-in areas. These results indicate that the relocation of local governments can be an effective place-based policy to improve economic growth and urbanization.

Is there an association between family members’ season of birth that could influence birth seasonality? Evidence from Spain and France

The number of births varies by season. Research on birth seasonality has shown that women’s season of birth somehow influences that of their children, but factors underlying the intergenerational transmission of birth seasonality remain unknown. With data from Spain and France, we analysed the possibility of transmission of birth season between generations, testing whether relatives tended to be born in the same season. Results indicated that there was an association—a similarity—between parents’ and children’s birth seasons, partially explaining the stability of seasonal patterns over time. This association also existed between parents’ birth seasons. While parents’ association is directly explained by an excess of marriages with spouses born in the same month, the overall association may be explained by two facts: different socio-demographic groups show differentiated birth patterns, and relatives share socio-demographic features. Birth season seems to be related to family characteristics, which should be controlled for when assessing birth-month effects on subsequent social/health outcomes.

Does rail transit access affect firm dynamics? Analysis of firm births and closures in Maryland, USA

Firm birth and firm closure are two interrelated dynamics relevant to measuring economic growth, yet most studies focus on firm birth only. Public transportation infrastructure may facilitate firm birth, but it may also avert firm closure through improved accessibility that can consequently lead to increased local density hence agglomeration economies. This study analyzes firm births and firm closures using the National Establishment Time Series (NETS) panel data from Maryland from 1991 to 2009. By examining both birth and closure patterns, this study estimates the likelihood of firm retention for areas in proximity to passenger rail stations of multiple levels of maturity, while controlling for a number of potentially confounding factors. Positive and statistically significant relationships are found between proximity to the passenger rail stations and the rates of firm births in Maryland, regardless of differences in the level of maturity of stations. From 1991 to 2009, areas within close proximity to passenger rail stations in Maryland experienced a wide range of rates of growth in firm density, depending on the year of station opening. The results suggest that well after the introduction of rail stations, areas near passenger rail stations gain belated economic benefits shown by higher likelihood of firm retention around the mature rail stations opened before 1990. In comparison, areas near the less mature stations that opened after 1990 had predominantly lower likelihood of firm retention. Planners and policymakers should be proactive in directing development near rail stations by adopting a variety of measures and policies that support or are at least consistent with transit-oriented development (TOD).

Season of Birth in Patients with Schizophrenia in Thailand.

An excess of schizophrenia births in the winter or spring is a well-known finding in Western studies; however, few studies from equatorial regions have been done. Our purpose is to investigate the seasonality of schizophrenia births in Thailand. This was a retrospective study in which patients with schizophrenia were identified from computerized records at Thammasat University Hospital. The Edwards test was used to detect any birth seasonality patterns among the patients with schizophrenia. Subsequently, the data were compared against the general population birth month data to examine potential seasonal effects using the Walter-Elwood seasonality test. There are 949 patients with schizophrenia, with a mean age of 39.3 years. The results demonstrate no evidence of distinctive seasonality in birth patterns among patients with schizophrenia (P = .329). The overall monthly distribution of births did not differ between the general population and patients with schizophrenia (P = .365). In Thailand, a tropical country, there does not appear to be an effect of season of birth and the later development of schizophrenia.

Preterm births prevalence during the COVID-19 pandemic in Brazil: results from the national database

The SARS-CoV-2 (COVID-19) pandemic impacted the health systems between and within countries, and in the course of the pandemic sexual and reproductive health services were the most disrupted. Findings from high-income settings have reported significant changes in preterm birth prevalence during the pandemic period. To understand the possible effects of the COVID-19 pandemic on preterm birth numbers at the Brazilian national level. We compare the number of preterm deliveries during the COVID-19 pandemic period (2020 and 2021) with previous years. We conducted a population-based cross-sectional study taking the period from January 2017 to December 2021 to account. We use individual-level live births data from the Brazilian Live Birth Information System (SINASC), and we estimate the odds ratio (OR) of preterm deliveries using propensity score weighting analysis in Brazil and its regions. During the study period (from 2017 to 2021), about 2.7 million live births were recorded per year, and the missing value for gestational age at delivery was less than 1.5%. The preterm birth prevalence slightly increased during the COVID-19 pandemic compared to the pre-pandemic period (11.32% in 2021 vs 11.09% in 2019, p-value < 0.0001). After adjusting for sociodemographic variables, the OR of preterm births in Brazil has significantly increased, 4% in 2020 (OR: 1.04 [1.03–1.05] 95% CI, p-value < 0.001), and 2% in 2021(OR: 1.02 [1.01–1.03] 95% CI, p-value < 0.001), compared to 2019. At the regional level, the preterm birth pattern in the South, Southeast and Northeast regions show a similar pattern. The highest odds ratio was observed in the South region (2020 vs 2019, OR: 1.07 [1.05–1.10] 95% CI; 2021 vs 2019, OR: 1.03 [1.01–1.06] 95% CI). However, we also observed a significant reduction in the ORs of preterm births in the northern region during the COVID-19 pandemic (2020 vs 2019, OR: 0.96 [0.94–0.98] 95% CI) and (2021 vs 2019, OR: 0.97 [0.95–0.99] 95% CI). Our analysis shows that the pandemic has increased regional variation in the number of preterm births in Brazil in 2020 and 2021 compared to the pre-pandemic years.

Which month to give a birth? The analysis on birth seasonality of China

A series of medical and biological studies have identified a strong link between the season during which a child is born and early childhood development and adult health. While providing an explanation for the seasonal determinants of birth remains one of the key challenges for demographers, understanding seasonal birth peaks and troughs can inform both public health planning and efforts to prevent childhood diseases. The seasonality of births varies across and within countries. Nonetheless, there has been scant research into the seasonality of births in China. This study takes an in depth look at the seasonal fluctuations in China’s births since 1960 and investigates the effects on seasonality of several key factors such as parity, residence (urban or rural area), and changes to fertility policies. Traditionally, winter has been the peak season of births in China, while spring and summer have been lean seasons, a pattern which is quite different than patterns in Europe and the United States. After 1990, the sweeping implementation of one-child policy and the wider use of modern contraceptives among Chinese women prompted a fundamental shift in the seasonality of births, with the deviation of births from month to month gradually diminishing over time. People's self-control may serve as a key determinant accounting for such seasonal changes. First births exhibit pronounced and steady seasonality, while second and subsequent births follow a vague seasonal pattern, suggesting that later births are more likely affected by self-choice and self-intervention. The analysis also reveals that the monthly distribution pattern of second births experienced a dramatic change following the roll-out of the selective-two-child policy and the Universal Two-child Policy in 2014 and 2016, changes that reflects the adjustments people made to achieve their fertility plans under the new policy.

Explaining third birth patterns in India: causal effects of sibling sex composition

Explaining third birth patterns in India: causal effects of sibling sex composition

Application of in Vitro Membrane Pulmonary Oxygenation Technology (ECMO) in Neonatal Respiratory Failure

Objective: To explore the application of Extracorporeal Membrane Oxygenation technology (ECMO) in neonatal respiratory failure and provide guidance for future ECMO technology for critically ill newborns. Methods: Retrospective analysis of the basic data, ECMO support process, and long-term neurological development of nine children supported by ECMO at Zhongshan People’s Hospital from January 2015 to August 2021. Results: From January 2015 to August 2021, the number of admissions to the neonatal department of our hospital was 10,325, with 433 cases of neonatal respiratory failure, which was in line with ECMO support indication of 21 cases, of which 12 were non-ECMO groups and 12 were ECMO groups. In nine cases, the differences in sex, birth weight, gestational age, birth pattern, Apgar score, NCIS score, OI value, hospitalization days, mortality rate, and incidence of intracranial bleeding were not statistically significant (P&gt;0.05). However, the average daily hospitalization cost for children in the ECMO group was significantly higher than that in the non-ECMO group, and the difference was statistically significant (P&lt;0.05). ECMO after 12 h operation, arterial oxygen pressure, and intravenous oxygen saturation are substantially enhanced, while arterial carbon dioxide pressure oxygenation index is considerably reduced, with a statistically significant difference (P&lt;0.05). ECMO pre-operation survival group lactic acid (6.46±2.70) was lower than the death group (17.66±14.62), after operation lactic acid decreased significantly, and after ECMO operation of the death group lactic acid showed an increase in conductivity. During the early stage of ECMO establishment, PT and APTT rapidly rise, while FIB decline. The ACT of both groups of children increased in the early stages of ECMO establishment and then gradually declined. In the ECMO group, seven children survived to discharge, six had no neurological developmental problems, and one had residual neurological sequelae. Conclusion: ECMO can be employed as a complementary supportive treatment for newborns with respiratory failure, and the oxygenation condition can be effectively improved for newborns with respiratory failure who have failed to respond to traditional treatment.

Comparing Cesarean Birth Utilization Between US Hospitals: A Demonstration of the Robson Ten-Group Classification System for Use in Quality Improvement and Benchmarking.

The World Health Organization-endorsed Robson Ten-Group Classification System (TGCS) is a standard reporting mechanism for cesarean birth, yet this approach is not widely adopted in the United States. To describe the application and utility of the TGCS to compare hospital-level cesarean births rates, for use in quality improvement and benchmarking. We conducted a descriptive, secondary data analysis of the Consortium on Safe Labor dataset using data from 228 438 women's births, from 2002 to 2008, in 12 sites across the United States. We stratified births into 10 mutually exclusive groups and calculated within-group proportions of group size and cesarean birth rates for between-hospital comparisons of cesarean birth, trial of labor after cesarean (TOLAC), and labor induction utilization. There is variation in use of cesarean birth, labor induction, and TOLAC across the 12 sites. The TGCS provides a method for between-hospital comparisons, particularly for revealing usage patterns of labor induction, TOLAC, and cesarean birth. Adoption of the TGCS in the United States would provide organizations and quality improvement leaders with an effective benchmarking tool to assist in reducing the use of cesarean birth and increasing the support of TOLAC.

On a Statistical Model Useful for Demographics: Estimating the Mean Number of Children Ever Born Through the Distribution of Male Births with an Application to Data from India

The connection between male births and fertility can be easily linked with demographic transition and in defining the population distribution. In this context, it is necessary to understand the birth patterns in Indian societies which are governed by some or the other probability distributions. Although child birth is a biological process but it is very much influenced by a number of social, economic, cultural and psychological factors. Numerous demographers have proposed mathematical models to predict the number of male and female births during a given time period taking into consideration the various factors. Traditionally, estimating current levels and future trends of mean number of births is done using various life tables, cohort-component method, time-series analysis, micro-simulations, structural modeling, expert analysis, historical error analysis and also using an appropriate probability model and testing the model on real data. In the present study we developed a model for estimating the mean number of children ever born through the join probability distribution with its application for male births among the females of Uttar Pradesh and Bihar. The reasons of selecting these two states were their huge population and high total fertility rates. The model fits to the data of these two states, therefore it would be a good fit for the other states too, which shows the efficiency and applicability of the model. The applicability of this model has been illustrated on real data obtained from the National Family Health Survey-3 (2005–06). The various estimates of the parameters have been obtained by using the method of moments and suitability of the proposed model has been tested using the ‘goodness of fit’ criteria.

Association between season of conception, month of conception with preterm birth in China: a population-based retrospective cohort study

BackgroundSeasonal patterns of preterm birth were identified in previous studies, but the effect of conception season on preterm birth has not been extensively studied. Based on the notion that the etiological roots of preterm birth lie in the beginning of pregnancy, we did a population-based retrospective cohort study in Southwest China to examine the effects of season of conception and month of conception on preterm birth.MethodsWe did a population-based retrospective cohort study in women (aged 18–49) who participated in the NFPHEP from 2010 to 2018, and had a singleton livebirth in southwest China. According to the time of the last menstruation reported by the participants, month of conception and season of conception were then ascertained. We used multivariate log-binomial model to adjust the potential risk factors for preterm birth and obtained adjusted risk ratio (aRR) and 95% confidence intervals (95%CI) for conception season, conception month and preterm birth.ResultsAmong 194 028 participants, 15 034 women had preterm birth. Compared with pregnancies that were conceived in the summer, pregnancies that were conceived in the spring, autumn and winter had the higher risk of preterm birth (Spring: aRR = 1.10, 95% CI: 1.04–1.15; Autumn: aRR = 1.14, 95% CI: 1.09–1.20; Winter: aRR = 1.28, 95% CI: 1.22–1.34) and also had a higher risk of early preterm birth (Spring: aRR = 1.09, 95% CI: 1.01–1.18; Autumn: aRR = 1.09, 95% CI: 1.01–1.19; Winter: aRR = 1.16, 95% CI: 1.08–1.25). Pregnancies in December, and January had a higher risk of preterm birth and early preterm birth than pregnancies that were conceived in July.ConclusionsOur study found that preterm birth was significantly related to season of conception. Preterm and early preterm birth rates were the highest among pregnancies that were conceived in winter, and the lowest among pregnancies in summer.

Prevalence and County-Level Distribution of Births in Catholic Hospitals in the US in 2020

This study uses American Hospital Association data to examine the volume and distribution of births in Catholic US hospitals and quantify county-level patterns of Catholic and non-Catholic hospital births.

Short-active gestational photoperiod reduces effortful choice behavior in mice, partial normalization by d-amphetamine.

Seasonal birth patterns consistently implicate winter gestation as a risk factor for several psychiatric conditions. We recently demonstrated that short-active (SA; 19:5 light:dark)-i.e., "winter-like"-photoperiod exposure across gestation and early life (E0-P28) induces psychiatrically relevant behavioral abnormalities in adult mice, including reduced immobility in the forced swim test (FST) and effortful amotivation. It is unknown, however, whether these effects were driven primarily by prenatal or postnatal mechanisms, and whether perinatal SA photoperiod would similarly reduce effort expenditure in a task relevant to everyday decision-making. We first tested male and female mice exposed to either gestational (E0-P0) or postnatal (E0-P28) SA photoperiod in the FST to determine whether the previously observed alteration was driven primarily by prenatal versus postnatal photoperiod. We then assessed whether SA gestational photoperiod reduces effortful choice behavior in the cross-species effort-based decision-making task (EBDMT) and whether any such deficit could be remediated by d-amphetamine (0.1 and 0.3 mg/kg, i.p.). Mice exposed to prenatal, but not postnatal, SA photoperiod exhibited reduced FST immobility relative to controls and also demonstrated condition-dependently reduced preference for high-effort/high-reward versus low-effort/low-reward contingencies in the EBDMT. This effortful choice deficit was normalized by 0.1 mg/kg amphetamine. These data: (1) suggest a greater contribution of gestational versus postnatal light conditions to the behavioral effects of perinatal SA photoperiod; and (2) implicate altered dopamine signaling in the behavioral phenotype of the SA-born mouse and possibly in the etiology of winter gestation-associated cases of psychiatric disease.

Confounding by Conception Seasonality in Studies of Temperature and Preterm Birth: A Simulation Study.

Seasonal patterns of conception may confound acute associations between birth outcomes and seasonally varying exposures. We aim to evaluate four epidemiologic designs (time-stratified case-crossover, time-series, pair-matched case-control, and time-to-event) commonly used to study acute associations between ambient temperature and preterm births. We conducted simulations assuming no effect of temperature on preterm birth. We generated pseudo-birth data from the observed seasonal patterns of birth in the United States and analyzed them in relation to observed temperatures using design-specific seasonality adjustments. Using the case-crossover approach (time-stratified by calendar month), we observed a bias (among 1,000 replicates) = 0.016 (Monte-Carlo standard error 95% CI: 0.015-0.018) in the regression coefficient for every 10°C increase in mean temperature in the warm season (May-September). Unbiased estimates obtained using the time-series approach required accounting for both the pregnancies-at-risk and their weighted probability of birth. Notably, adding the daily weighted probability of birth from the time-series models to the case-crossover models corrected the bias in the case-crossover approach. In the pair-matched case-control design, where the exposure period was matched on gestational window, we observed no bias. The time-to-event approach was also unbiased but was more computationally intensive than others. Most designs can be implemented in a way that yields estimates unbiased by conception seasonality. The time-stratified case-crossover design exhibited a small positive bias, which could contribute to, but not fully explain, previously reported associations.