Reproductive Patterns Research Articles

Life-history characteristics and historical factors are important to explain regional variation in reproductive traits and genetic diversity in perennial mosses.

Plants have evolved an unrivalled diversity of reproductive strategies, including variation in the degree of sexual vs. clonal reproduction. This variation has important effects on the dynamics and genetic structure of populations. We examined the association between large-scale variation in reproductive patterns and intraspecific genetic diversity in two moss species where sex is manifested in the dominant haploid generation and sex expression is irregular. We predicted that in regions with more frequent realized sexual reproduction, populations should display less skewed sex ratios, should more often express sex and should have higher genetic diversity than in regions with largely clonal reproduction. We assessed reproductive status and phenotypic sex in the dioicous long-lived Drepanocladus trifarius and D. turgescens, in 248 and 438 samples across two regions in Scandinavia with frequent or rare realized sexual reproduction, respectively. In subsets of the samples, we analysed genetic diversity using nuclear and plastid sequence information and identified sex with a sex-specific molecular marker in non-reproductive samples. Contrary to our predictions, sex ratios did not differ between regions; genetic diversity did not differ in D. trifarius and it was higher in the region with rare sexual reproduction in D. turgescens. Supporting our predictions, relatively more samples expressed sex in D. trifarius in the region with frequent sexual reproduction. Overall, samples were mostly female. The degree of sex expression and genetic diversity differed between sexes. Sex expression levels, regional sex ratios and genetic diversity were not directly associated with the regional frequency of realized sexual reproduction, and relationships and variation patterns differed between species. We conclude that a combination of species-specific life histories, such as longevity, overall degree of successful sexual reproduction and recruitment, and historical factors are important to explain this variation. Our data on haploid-dominated plants significantly complement plant reproductive biology.

Reconsidering reproductive patterns in a model dissociated species, the red-sided garter snake: Sex-specific and seasonal changes in gonadal steroidogenic gene expression.

Sex steroid hormones are powerful regulators of reproductive behavior and physiology in vertebrates, and steroidogenesis has distinct sex- and season-specific patterns ultimately dictated by the expression of key enzymes. Most comparative endocrinology studies, however, focus only on circulating levels of sex steroids to determine their temporal association with life-history events in what are termed associated reproductive patterns. The red-sided garter snake (Thamnophis sirtalis parietalis) is a notable exception; this species exhibits maximal sex behavior decoupled from maximal sex steroid production and gametogenesis in what is termed a dissociated reproductive pattern. And while this is true for male red-sided garter snakes and their production of testosterone, females have maximal estradiol production during peak breeding (spring) but only immediately after mating. Here, we demonstrate that expression of ovarian aromatase (conversion of androgens to estrogens) matches the established seasonal hormone pattern in females. Additionally, steroidogenic gene expression in the ovary is broadly reduced if not suppressed compared to the testis throughout the active year. Bizarrely, male red-sided garter snakes demonstrate an unexplained pattern of steroidogenic gene expression in the testis. StAR (import of cholesterol to steroidogenesis) is maximally expressed in spring, yet Hsd17b3 expression (conversion of androstenedione to testosterone) is highest in summer, with the latter matching the established summer peak in male testosterone. The function of elevated StAR in spring is unknown, but our results suggest a decoupling between maximal StAR expression and testosterone biosynthesis (Hsd17b3 expression). We also purport that the reproductive pattern binary should be reassessed given its lack of fit for many vertebrate species that demonstrate seasonal, mixed patterns of (a)synchrony between circulating sex hormones and reproductive behavior.

Anaerobic Membrane Bioreactor (AnMBR) for the Removal of Dyes from Water and Wastewater: Progress, Challenges, and Future Perspectives

The presence of dyes in aquatic environments can have harmful effects on aquatic life, including inhibiting photosynthesis, decreasing dissolved oxygen levels, and altering the behavior and reproductive patterns of aquatic organisms. In the initial phase of this review study, our aim was to examine the categories and properties of dyes as well as the impact of their toxicity on aquatic environments. Azo, phthalocyanine, and xanthene are among the most frequently utilized dyes, almost 70–80% of used dyes, in industrial processes and have been identified as some of the most commonly occurring dyes in water bodies. Apart from that, the toxicity effects of dyes on aquatic ecosystems were discussed. Toxicity testing relies heavily on two key measures: the LC50 (half-lethal concentration) and EC50 (half-maximal effective concentration). In a recent study, microalgae exposed to Congo Red displayed a minimum EC50 of 4.8 mg/L, while fish exposed to Disperse Yellow 7 exhibited a minimum LC50 of 0.01 mg/L. Anaerobic membrane bioreactors (AnMBRs) are a promising method for removing dyes from water bodies. In the second stage of the study, the effectiveness of different AnMBRs in removing dyes was evaluated. Hybrid AnMBRs and AnMBRs with innovative designs have shown the capacity to eliminate dyes completely, reaching up to 100%. Proteobacteria, Firmicutes, and Bacteroidetes were found to be the dominant bacterial phyla in AnMBRs applied for dye treatment. However, fouling has been identified as a significant drawback of AnMBRs, and innovative designs and techniques are required to address this issue in the future.

Advances in the understanding of Blattodea evolution: Insights from phylotranscriptomics and spermathecae

Cockroaches, an ancient and diverse group of insects on earth that originated in the Carboniferous, displays a wide array of morphology or biology diversity. The spermatheca is an organ of the insect reproductive system; the diversity of spermathecae might be the adaption to different mating and sperm storage strategies. Yet a consensus about the phylogenetic relationships among the main lineages of Blattodea and the evolution of spermatheca has not been reached until now. Here we added the transcriptome data of Anaplectidae for the first time and supplemented other family level groups (such as Blaberidae, Corydiidae) to address the pending issues. Our results showed that Blattoidea was recovered as sister to Corydioidea, which was strongly supported by molecular evidence. In Blattoidea, (Lamproblattidae + Anaplectidae) + (Cryptocercidae + Termitoidae) was strongly supported by our molecular data. In Blaberoidea, Pseudophyllodromiidae and Blaberidae were recovered to be monophyletic, while Blattellidae was found to be paraphyletic with respect to Malaccina. Ectobius sylvestris + Malaccina discoidalis formed the sister group to other Blaberoidea; Blattellidae (except Malaccina discoidalis) + Nyctiboridae was found as the sister of Blaberidae. Corydiidae was recovered to be non-monophyletic due to the embedding of Nocticola sp. Our ASR analysis of spermatheca suggested that primary spermathecae were present in the common ancestor, and it transformed at least six times during the evolutionary history of Blattodea. The evolution of spermatheca could be described as a unidirectional trend: the increased size to accommodate more sperm. Furthermore, major splits within the existing genera of cockroaches occurred in the Upper Paleogene to Neogene. Our study provides strong support for the relationship among three superfamilies and offers some new insights into the phylogeny of cockroaches. Meanwhile, this study also provides basic knowledge on the evolution of spermathecae and reproductive patterns.

An experimental analysis of density dependence in meadow voles: Within-season and delayed effects.

Wild mammal populations exhibit a variety of dynamics, ranging from fairly stable with little change in population size over time to high-amplitude cyclic or erratic fluctuations. A persistent question in population ecology is why populations fluctuate as they do. Answering this seemingly simple question has proven to be challenging. Broadly, density-dependent feedback mechanisms should allow populations to grow at low density and slow or halt growth at high density. However, experimental tests of what demographic processes result in density-dependent feedback and on what timescale have proven elusive. Here, we used replicated density perturbation experiments and capture-mark-recapture analyses to test density-dependent population growth in populations of meadow voles (Microtus pennsylvanicus) during the summer breeding season by manipulating founding population density and observing the pattern of survival, reproduction, and population growth. High population density had no consistent effect on survival rates but generally negatively influenced recruitment and population growth rates. However, these density-dependent effects varied within the breeding season and across years. Our study provides evidence that density-dependent feedback mechanisms operate at finer time scales than previously believed and that process, additively with delayed year effects, is key to understanding multiyear population demography.

The authoritarian narrator: China's power projection and its reception in the Gulf

Abstract This article argues that transregional communication mechanisms and the diffusion of narratives are important co-drivers towards autocratization. Offering a look beyond the ‘material’ in the study of global authoritarianism, it makes two conceptual arguments. It shows show transregional authoritarian practices are often discursively reinforced. Moreover, it demonstrates how narratives and their transregional diffusion are a form of authoritarian image management and a tool for fostering authoritarian stability. Departing from the basic assumption of authoritarian diffusion, the article is guided by two questions: which narratives of supremacy are used by the Chinese government in the context of the pandemic? And how are these narratives received, reproduced and contested in the Gulf? Based on a qualitative analysis of more than 3,000 media outlets (March–May 2020) from China and the Gulf region, the article shows how China strategically promotes authoritarian narratives regarding its international role, by telling stories of supremacy and heroism and by narratively conjuring a new world order. Moreover, it shows how the Chinese narratives are diffused to Iran, Saudi-Arabia, the United Arab Emirates and Qatar and depicts the different patterns of reception, reproduction and contestation.

Précis of Movies on Our Minds

Abstract Movies on Our Minds (Cutting, 2021) provides structural analyses of popular, English-language cinema and maps them onto biological and psychological bases. It progresses from the details of optics and screen projection; through transitions and shots; on to scenes, montages, and syntagmas; and finally to larger narrative units and the flow of patterns of elements across whole movies. It focuses on changes in all of those patterns across a century, ascribing them to evolution. That evolution, akin to Darwinian evolution, is hallmarked by patterns of reproduction with inheritance, variation, and selection of traits over time. Two forces appear to have guided this evolution: the matching of elements of film form to predilections of the biology of our visual systems, and their matching to predilections of our cognition, particularly as it has been shaped by visual culture.

Factors that shape large‐scale gradients in clonality

AbstractAimMany plant species reproduce clonally. However, ecologists still have much to learn about the factors that shape large‐scale patterns in plant clonal growth and reproduction, especially in the southern hemisphere. We addressed this knowledge gap by quantifying relationships between reproductive mode and a suite of plant characteristics and environmental variables.LocationAustralia.TaxonSpermatophytes.MethodsWe used data for 914,456 species‐site combinations (including 4116 unique species) in Australia to quantify the bivariate relationships between the probability of species having clonal reproduction and four plant characteristics and 16 environmental variables, using phylogenetic logistic regressions. We also compared the relative effects across plant characteristics and environmental variables groups through principal component analysis and phylogenetic logistic regressions.ResultsThe probability of species having clonal reproduction was much more strongly related to plant characteristics than to environmental variables. Short, herbaceous plants and monocots were more likely to have clonal reproduction and were more common in environments with low temperatures, low solar radiation, high moisture availability, high net primary productivity (NPP) and high soil organic carbon and nitrogen contents. Tall, woody plants and eudicots tended to have only sexual reproduction, and were more common in dry and soil impoverished environments.Main conclusionsOur results advance the understanding of the factors that shape large‐scale patterns in plant reproduction strategy. For example, the fact that clonality is more common in shorter, herbaceous species suggests that clonality can be added to the suite of traits that align species on the fast‐slow continuum. The fact that clonal reproduction is more tightly correlated with moisture availability, NPP and soil nutrients than climatic extremes and variations suggests that clonal reproduction may be better understood as a strategy for population expansion in resource abundant sites than as a strategy for reproductive assurance under environmental stress.

정조대왕의 효행과 콘텐츠로의 재현

정조대왕의 효행과 콘텐츠로의 재현

Trade-off between thermal preference and sperm maturation in a montane lizard

Temperature is a key abiotic factor that influences performance of several physiological traits in ectotherms. Organisms regulate their body temperature within a range of temperatures to enhance physiological function. The capacity of ectotherms, such as lizards, to maintain their body temperature within their preferred range influences physiological traits such as speed, various reproductive patterns, and critical fitness components, such as growth rates or survival. Here, we evaluate the influence of temperature on locomotor performance, sperm morphology and viability in a high elevation lizard species (Sceloporus aeneus). Whereas maximal values for sprint speed coincides with field active and preferred body temperature, short-term exposure at the same range of temperatures produces abnormalities in sperm morphology, lower sperm concentration and diminishes sperm motility and viability. In conclusion, we confirmed that although locomotor performance is maximized at preferred temperatures, there is a trade-off with male reproductive attributes, which may cause infertility. As a consequence, prolonged exposure to preferred temperatures could threaten the persistence of the species through reduced fertility. Persistence of the species is favored in environments with access to cooler, thermal microhabitats that enhance reproductive parameters.

Contributors to Preterm Birth: Data from a Single Polish Perinatal Center

Preterm birth may result from overlapping causes including maternal age, health, previous obstetric history and a variety of social factors. We aimed to identify factors contributing to preterm birth in respect to new social and environmental changes in the reproductive patterns. Our cross-sectional study included 495 mother-infant pairs and was based on maternal self-reporting in an originally developed questionnaire. Neonates were divided into two groups: 72 premature babies (study group) and 423 full-term babies (control group). We analyzed maternal, sociodemographic and economic characteristics, habits, chronic diseases, previous obstetric history and pregnancy complications. For statistical analysis, Pearson's Chi-squared independence test was used with a statistical significance level of 0.05. Preterm births were more common among mothers living in villages (p < 0.001) and with lower education level (p = 0.01). Premature births were also positively associated with mothers who were running their own businesses (p = 0.031). Mothers with a history of previous miscarriages gave birth at a significantly older age (p < 0.001). The most frequent pregnancy complications were hypothyroidism (41.4%), pregestational and gestational diabetes mellitus (DM; 17.8%) and hypertension (8.1%). Pregestational DM significantly influenced the occurrence of prematurity (p < 0.05). Pregestational DM, being professionally active, a lower education level and living outside cities are important risk factors of prematurity.

Determinants of time to first marriage and birth intervals among women of child bearing age in Dabat Health and demographic surveillance system site, Northwest Ethiopia.

Event histories such as marriage and birth have been used to study fertility behavior of women. Understanding the timing of these events provide insight to reproductive patterns of the population. Thus, the aim of this study was to assess the timing of marriage and durations of birth intervals and their associated factors, and and to examine their effects on the current fertility among women in Dabat health and demographic surveillance system site, Northwest Ethiopia. A community based cross-sectional survey was carried out in the beginning of 2020 among 1649 women of reproductive age group. Data were collected using structured and interviewer administered questionnaire. The parametric survival analysis was employed to estimate the relationships among socioeconomic and demographic variables with outcome variables, the timing of age at first marriage and duration of birth intervals. This study confirmed that median age at first marriage was the lowest estimated at 15 years which was below the national and regional average. The result of the study also revealed that married women waited almost a median duration of three years for their first, second, third and fourth child which was increased to nearly four years for three years preceding the survey. The parametric survival analysis showed woman's education, occupation, and current age were the predictors of age at first marriage. divorce experience, women empowerment and marriage cohort were the determinant factors of first birth interval; women education, child death, and ideal number of children were the predictors of second and third birth intervals; and media exposure and child death experience of women were predictors of fourth birth interval. The study indicated that median age at first marriage was the lowest though the successive birth intervals were longer. The survival analysis identified women's education, occupation, child death and ideal number of children affected the timing of age at first marriage and duration of birth intervals. Hence, encouraging women for higher education and giving opportunity to women in employments may contribute for delaying age at first marriage and increasing the duration of birth intervals which in turn slowing down the fertility of women.

Maternal Energy Depletion Is Buffered among Malnourished Women in Punjab, Pakistan ,

Women's nutritional status is believed to deteriorate with increasing reproductive stress (so-called maternal depletion). To evaluate this phenomenon, a new theoretical framework has been suggested that incorporates the concepts of a full reproductive cycle, relative lengths of potential depletion and repletion phases, and initial plane of nutrition. We developed the corresponding statistical model and tested predictions provided by the framework about the effect of reproductive pattern on maternal overall weight change (deltaW) during one reproductive cycle. Seventy-six Pakistani women were classified as well-nourished, marginally nourished or malnourished. The relationship between deltaW and length of all phases of the reproductive cycle, each of which is characterized by varying degrees of reproductive stress, was evaluated with multiple regression analysis. Across the reproductive cycle, well-nourished women had a slight weight increase. Surprisingly, malnourished women gained weight in contrast to marginally nourished women. Also surprisingly, for the latter two groups, periods of moderate reproductive stress were associated with weight loss but periods of high reproductive stress were associated with weight gain. Mechanisms such as efficiency and nutrient partitioning are discussed.

Placentation in the Mexican scincid lizard Plestiodon brevirostris (Squamata: Scincidae).

Viviparity is the reproductive pattern in which females gestate eggs within their reproductive tract to complete their development and give birth to live offspring. Within extant sauropsids, only the Squamata (e.g., snakes, lizards, and amphisbaenians) evolved viviparity, representing 20% of the existing species. The genus Plestiodon is represented by 43 species and is one of the most widely distributed genera of the Scincidae in Mexico. The goal of this research has been to determine the placental morphology and ontogeny during gestation in the lizard Plestiodon brevirostris. Specimens were dissected to obtain the embryonic chambers and the embryos were categorized to carry out the correlation between the development stage and the placenta development. The embryonic chambers were processed using the conventional histological technique for light microscopy. The identified embryonic stages were 4, 29, 34, 36, and 39. A thin eggshell surrounds the egg in early developmental stages; however, this structure is already absent in the embryonic hemisphere during the developmental stage 29. The results revealed that P. brevirostris is a lecithotrophic species, but a close maternal-fetal relationship is established by tissue apposition. Ontogenically, the placental types that form in the embryonic hemisphere are the chorioplacenta, choriovitelline placenta, and chorioallantoic placenta; whereas the omphaloplacenta is formed in the abembryonic hemisphere. The structure of the chorioallantoic placenta in P. brevirostris suggests that it may play a role during gas exchange between the mother and the embryo, due to the characteristics of the epithelia that comprise it. The structure of embryonic and maternal epithelia of the omphaloplacenta suggests a role in the absorption of the eggshell during gestation and possibly in the transport or diffusion of some nutrients. In general, it is evident that ontogeny and placental characteristics of P. brevirostris match those of other species of viviparous lecithotrophic scincids.

Oak masting drivers vary between populations depending on their climatic environments

Large interannual variation in seed production, called masting, is very common in wind-pollinated tree populations and has profound implications for the dynamics of forest ecosystems and the epidemiology of certain human diseases.1,2,3,4,5 Comparing the reproductive characteristics of populations established in climatically contrasting environments would provide powerful insight into masting mechanisms, but the required data are extremely scarce. We built a database from an unprecedented fine-scale 8-year survey of 150 sessile oak trees (Quercus petraea) from 15 populations distributed over a broad climatic gradient, including individual recordings of annual flowering effort, fruiting rate, and fruit production. Although oak masting was previously considered to depend mainly on fruiting rate variations,6,7 we show that the female flowering effort is highly variable from year to year and explains most of the fruiting dynamics in two-thirds of the populations. What drives masting was found to differ among populations living under various climates. In soft-climate populations, the fruiting rate increases initially strongly with the flowering effort, and the intensity of masting results mainly from the flowering synchrony level between individuals. By contrast, the fruiting rate of harsh-climate populations depends mainly on spring weather, which ensures intense masting regardless of the flowering synchronization level. Our work highlights the need for jointly measuring flowering effort and fruit production to decipher the diversity of masting mechanisms among populations. Accounting for such diversity will be decisive in proposing accurate, and possibly contrasted, scenarios about future reproductive patterns of perennial plants with ongoing climate change and their numerous cascading effects.

Life history traits for Ophryotrocha craigsmithi (Wiklund, Glover &amp; Dahlgren, 2009), a candidate species in integrated multitrophic aquaculture

Ophryotrocha craigsmithi (Wiklund, Glover &amp;amp; Dahlgren, 2009) has repeatedly been observed in high densities at salmonid fish farms in Norway and has been shown to feed on the organic waste released during fish production. This species has therefore been pointed out as a candidate for the benthic component of integrated multitrophic aquaculture (IMTA). Little is known about the life history traits of Ophryotrocha species found at greater depths in temperate waters. Insight into life traits is of key importance in evaluating the bio-mitigation and harvest potential of (benthic) species within IMTA systems. In this study, we aimed to describe key life history traits for O. craigsmithi, such as growth, reproductive pattern, and offset of reproduction. The main findings are as follows: (I) O. craigsmithi exhibits early sexual maturation and rapid growth, going from 5 to 16 mm in length in 8 weeks; (II) their estimated lifetime is approximately 15 weeks with a generation time of 4 weeks; (III) there are strong indications that they are gonochoric semicontinuous spawners; (IV) the majority of mature eggs ranged from 120 to 150 µm; and (V) the larvae developed into a free-swimming stage after approximately 1 week. To this end, we present a framework for assessing the suitability of deposit-feeding polychaetes as candidate species in IMTA, considering environmental adaptiveness, production potential, as well as carbon and nitrogen mitigation capacity. On the basis of this, O. craigsmithi shows a high suitability as an extractive farmed species in benthic IMTA.

Number of lifetime menses increases breast cancer occurrence in postmenopausal women at high familial risk

It is increasingly thought that part of human susceptibility to cancer is the result of evolutionary mismatches: our ancestors evolved cancer suppression mechanisms in a world largely different from our modern environments. In that context, it has been shown in cohorts from general Western populations that reproductive traits modulate breast cancer risk. Overall, the more menses women experience, the more at risk they are to develop postmenopausal breast cancer. This points towards an evolutionary mismatch but brings the question whether the reproductive pattern also modulates the breast cancer risk in menopausal women at high familial risk. We thus studied the influence of menses on breast cancer risk in a case–control study of 90 postmenopausal women (including BRCA1/2 and non BRCA1/2) nested within a cohort at high familial risk. We tested the association of the lifetime number of menses and the number of menses before first full-term pregnancy with postmenopausal breast cancer risk using Cox survival models. We showed that the total lifetime number of menses was significantly associated with postmenopausal breast cancer risk and associated with a quicker onset of breast cancer after menopause. Those results align with similar studies lead in general cohorts and suggest that the reproductive pattern modulates the familial risk of developing breast cancer after menopause. Altogether, those results impact how we envision breast cancer prevention and call for more research on how ecological and genetic factors shape breast cancer risk.

Consistent Monthly Reproduction and Completion of a Brooding Coral Life Cycle through Ex Situ Culture

The continuing impact of local and global stressors on coral reefs worldwide is prompting the exploration of novel approaches aimed at mitigating and improving the bleak future projections for corals. Ex situ aquaculture has the potential to provide a standardized supply of source corals to support active intervention-based research endeavours as well as complementary reef restoration initiatives. To effectively achieve this supply of coral, however, ex situ aquaculture systems need to be able to efficiently maintain reproducing colonies, and have the capacity to support each coral life stage. We monitored the monthly reproduction of the brooding coral, Pocillopora acuta, for one year in two distinct aquaculture systems: a natural seawater-supplied flow-through system (FTS) and an artificial seawater-supplied recirculating aquaculture system (RAS). The coral colonies in both aquaculture systems showed relatively consistent reproduction over time (on average &gt; 70% of all colonies reproducing each month) and maintained natural diel reproduction patterns even after 1 year of ex situ culture. Coral colony reproductive output and timing (i.e., lunar day of release) differed between aquaculture systems in some, but not all, seasons. Planulae released from colonies settled and grew to reproductive size after ~16 months of culture, resulting in the ex situ production of an F2 generation of a brooding coral within two distinct aquaculture systems. This demonstrated that the use of ex situ aquaculture could be directly applied to research, restoration, and conservation aimed at mitigating coral decline in a future marred by climate change and local impacts.

The Reproduction of Meretrix meretrix Clams in The Kambu River Estuary, Southeast Sulawesi

Meretrix meretrix is a degraded resource in Kendari Bay waters, but its reproductive pattern is not fully known.. This study aims to determine the level of gonad maturity, gonadal maturity index, fecundity and the size of the first gonad maturity of M. meretrix at the Kambu River estuary, Kendari Bay, Southeast Sulawesi. This research was carried out at the Kambu River estuary for 6 months from August 2021-January 2022. These clams were taken randomly representing all size classes as many as 300 birds during the study. M. meretrix were observed for gonad color and gonad development microscopically, then the length and weight of the gonads were measured using a caliper and analytical balance with an accuracy of 0.5 mm and 0.0001g, respectively. The results showed that the development of male and female gonads was relatively simultaneous, which was dominated by mature gonads (III-IV) in each month of observation. TKG I-V was found in every month of observation. The gonad maturity index of males and females were 4.92-6.00 and 5.53-6.32, respectively. The fecundity of M. meretrix ranged from 4882-85677 grains. The first mature size of the gonads of male and female M. meretrix is 20 mm.

Determinants of Duration of the First Birth Interval Using the Semi-parametric Survival Model in Uttar Pradesh, India: Evidence from NFHS

Background: First birth is an important phenomenon in women life. It not only affects the duration of the rest of birth intervals but also affects the reproductive pattern of women. The study aims to explore the determinants of the duration of the first birth interval.Subjects dan Method: The cross-sectional study data of 33,275 women married between the years 2005-2021 aged (15-49) years from Uttar Pradesh, were selected from NFHS-5 data. The NFHS-5 sample is a stratified two-stage sample. Socio-demographic, socio-economic and cultural factors were taken as independent variables. The dependent variable was the first birth interval variable. Data analysis was performed on SPSS version 23 software and R Programming language for graphical representation. Cox proportional hazard models were applied for analysis.Results: The mean age of women at first marriage was 19.4; SD=3.26 years and the mean age of women at first birth was 21.39; SD=3.24 years. The median duration of the first birth interval was22 months with an IQR of 14 until 32 months. Cox hazard proportional analysis revealed that religion, residence, (ever) fetal loss, age at first birth, heard family planning, and women or husband education were found to be statistically significant factors associated with the duration of the first birth interval (p&lt;0.001).Conclusion: There is a need to change the mindset of people towards the concept of the use of family planning methods to increase the length of the birth interval, regardless of various factors. This would help to increase the duration of the birth interval, improve the health of women and children, as well as help reduce population growth. Keywords: Uttar Pradesh, birth interval, semi-parametric, cox model, hazard plot. Correspondence:Jai Kishun, Department of Biostatistics and Health Informatics, Sanjay Gandhi Postgraduate Institute of Medical Sciences. Lucknow – 226014, India; email: jaikishan.stat@gmail.com