New Productive Technologies, Ethics and Legislation in Brazil: A Delayed Debate

This paper focuses on the debate about the utilization of new reproductive technologies in Brazil, and the paths taken in the Brazilian National Congress in an attempt to draw up legislation to regulate the clinical practice of human assisted reproduction. British documents, such as the Warnock Report and Human Fertilization and Embriology Authority (HFEA) are used for thorough reference. The analysis of the Law Projects in the National Congress, the Resolution by the Federal Medicine Council, Resolution 196/96 and documents by the Ministério Público (Public Prosecution Office), suppled the bases for the discussion. The principal question involved is the observation of different technical and moral prientations that influence the conduct of the issue in the legislative process. It is possible to observe that the main focus of the projects relates to the rights and interests of the children, to those possibly benefited by the technique and to embryo reduction. Very little attention has been directed to the issues of sexual and reproductive rights and to the health of the women submitted to the new reproductive techologies.     

Cancer in children born after frozen-thawed embryo transfer: A cohort study

BackgroundThe aim was to investigate whether children born after assisted reproduction technology (ART), particularly after frozen-thawed embryo transfer (FET), are at higher risk of childhood cancer than children born after fresh embryo transfer and spontaneous conception.Methods and findingsWe performed a registry-based cohort study using data from the 4 Nordic countries: Denmark, Finland, Norway, and Sweden. The study included 7,944,248 children, out of whom 171,774 children were born after use of ART (2.2%) and 7,772,474 children were born after spontaneous conception, representing all children born between the years 1994 to 2014 in Denmark, 1990 to 2014 in Finland, 1984 to 2015 in Norway, and 1985 to 2015 in Sweden. Rates for any cancer and specific cancer groups in children born after each conception method were determined by cross-linking national ART registry data with national cancer and health data registries and population registries. We used Cox proportional hazards models to estimate the risk of any cancer, with age as the time scale.After a mean follow-up of 9.9 and 12.5 years, the incidence rate (IR) of cancer before age 18 years was 19.3/100,000 person-years for children born after ART (329 cases) and 16.7/100,000 person-years for children born after spontaneous conception (16,184 cases). Adjusted hazard ratio (aHR) was 1.08, 95% confidence interval (CI) 0.96 to 1.21, p = 0.18. Adjustment was performed for sex, plurality, year of birth, country of birth, maternal age at birth, and parity. Children born after FET had a higher risk of cancer (48 cases; IR 30.1/100,000 person-years) compared to both fresh embryo transfer (IR 18.8/100,000 person-years), aHR 1.59, 95% CI 1.15 to 2.20, p = 0.005, and spontaneous conception, aHR 1.65, 95% CI 1.24 to 2.19, p = 0.001. Adjustment either for macrosomia, birth weight, or major birth defects attenuated the association marginally. Higher risks of epithelial tumors and melanoma after any assisted reproductive method and of leukemia after FET were observed.The main limitation of this study is the small number of children with cancer in the FET group.ConclusionsChildren born after FET had a higher risk of childhood cancer than children born after fresh embryo transfer and spontaneous conception. The results should be interpreted cautiously based on the small number of children with cancer, but the findings raise concerns considering the increasing use of FET, in particular freeze-all strategies without clear medical indications.Trial registrationTrial registration number: ISRCTN 11780826.

Nona Sargisian and colleagues investigate the risk of childhood cancer in children born after Frozen-Thawed Embryo Transfer in Denmark, Finland, Norway, and Sweden.     

Cryopreservation of oocytes and embryos: optimization by theoretical versus empirical analysis

Embryos and oocytes were first successfully cryopreserved more than 30 years ago. This procedure has come to be an important, almost essential component in the practice of assisted reproduction in animals and humans. Literally millions of animals of more than 20 species and undoubtedly hundreds of thousands of children have been born from frozen embryos. Nevertheless, there still remain shortcomings with methods used to cryopreserve oocytes and embryos. A wide variety of approaches has been used to try to improve and optimize methods of cryopreservation. These approaches range from the very basic to the completely empirical. Some investigators make use of rigorous mathematical formulations to define and describe the behavior of oocytes and embryos at subzero temperatures. Others conduct "trial-and-error" studies to improve the results by dint of many replicate experiments in which they examine the effects of various protective compounds, macromolecular supplements, and compare different cooling and warming conditions. This review considers both extremes.     

Determinants of current use of contraception and children ever born in Nepal

This paper explores the extent to which women's work for earnings, education and couple communication over family planning influence current contraceptive use and children ever born in Nepal. Data came from the 1996 Nepal Family Health Survey. The findings indicate that education has a significant positive influence on current use of contraception and a significant negative influence on children ever born. There was virtually no relationship between women working and current use of contraception. However, in full models, there was a significant positive relationship for women who earn cash for work on current use and a significant negative relationship for children ever born. Working alone does not increase contraceptive use or reduce the number of children ever born in Nepal, but earning cash for work does. The husband/couple variables also proved to be important determinants of current use of contraception and children ever born.     

Using people

Debate over human embryo research often has centered around the embryo's human status, with the assumption that beings accorded full humanhood may not be used as means to an end for other humans. Britain's Warnock Committee, for example, concluded that since the early embryo was potentially, not actually, a full human being, it legitimately could be treated, albeit briefly, as a means to an end for research purposes. Coughlan discusses the "Warnock principle," which precludes the use of human beings, the broader "Pauline principle," (from St. Paul's Epistle to the Romans), which forbids the doing of evil to achieve good, and the principle of double effect, which sets down the conditions under which the occasioning of evil is justifiable. He concludes that the Warnock and Pauline principles are untenable if construed as exceptionless. Anscombe questions Coughlan's understanding of the principle of double effect, and Coughlan defends his arguments.     

Assisted reproduction technology and long-term cardiometabolic health in the offspring

Ronald Ma and co-authors discuss Emma Norrman and colleagues’ accompanying research study on the health of children born with assisted reproductive technology.

Since the birth of the first baby with the aid of in vitro fertilization (IVF) in July 1978, more than 9 million children have since been born through IVF or other assisted reproduction technology (ART). From a report covering around 2/3 of world ART activity, it was estimated that more than 4.4 million ART cycles have been initiated between 2008 and 2010, which resulted in 1.14 million births during that period [1]. From 1997 to 2016, the numbers of recorded ART treatment have increased by 5.3-fold in Europe, 4.6-fold in the United States of America, and 3.0-fold in Australia and New Zealand [1]. In an accompanying study in PLOS Medicine, Emma Norrman and colleagues address the health of babies born after ART [2].While initially met with considerable skepticism and controversy, the large number of healthy babies born over the last 4 decades is testament to the success and safety of IVF, which has transformed the lives of many couples and families. Nevertheless, given the appreciation of the Developmental Origins of Health and Disease (DOHaD) hypothesis, which posits that insults during critical times of development (including in utero or early life) may modify an individual’s phenotype and alter later risk of disease in adulthood, as well as previous demonstration of potential epigenetic changes following ART, there has been rekindled interest in the potential long-term effects of ART on offspring health [3]. In a large retrospective Nordic population-based cohort study of all children born after ART between 1982 and 2007, there was no significant increase in overall cancer rates among children born after ART, compared to children born after spontaneous conception (SC) [4]. Questions have also been raised about the long-term cardiovascular health of offspring born after ART, as several mechanisms have been postulated to potentially contribute to impaired cardiovascular health, including suboptimal culture conditions, ART-induced epigenetic changes, as well as indirect effects through low birthweight, thereby contributing to altered cardiovascular phenotype [5] (Fig 1). A systematic review and meta-analysis did not show evidence of increased cardiovascular risk or diabetes for women following ART, though there was comparatively less data to address offspring risk [6]. In line with a recent systematic review and meta-analysis [7], previous small studies have found increased adiposity, cardiometabolic risk, and blood pressure among offspring born after ART, potentially due to altered gene expression [8,9]. However, issues regarding potential selection bias have been raised for the small studies included.Open in a separate windowFig 1A DOHaD perspective on the potential relationship between ART and later risk of T2D and CVD.The putative link is highlighted by the dotted outline. ART, assisted reproduction technology; CVD, cardiovascular disease; DOHaD, Developmental Origins of Health and Disease; EDCs, endocrine-disrupting chemicals; GDM, gestational diabetes; ICSI, intracytoplasmic sperm injection; IVF, in vitro fertilization; ncRNA, noncoding RNA; PCOS, polycystic ovary syndrome; T2D, type 2 diabetes. (adapted with permission from Ma and colleagues [13]).Norrman and colleagues conducted a large population-based study from the Committee of Nordic ART and Safety (CoNARTaS) cohort, which included all individuals born in Norway, Sweden, Finland, and Denmark between 1984 and 2015, including 122,429 children born after ART, and more than 7.5 million children born after SC, to investigate the risk of cardiovascular disease (CVD), diabetes, and obesity following ART compared to SC. Offspring were followed for a mean 8.6 years in children born after ART and 14.0 years for children born following SC. Although the crude rates for CVD and type 2 diabetes (T2D) were higher among children born after ART, there were no significant difference in rates after adjustment for measured confounders. The study noted a significant increase in the risk of obesity among children born to ART, though the risk was modest, with adjusted HR 1.14 (CI 1.06 to 1.23, p = 0.001). The design of the study also meant that it could not address whether any increased risk in the offspring might be related to maternal causes of infertility (such as polycystic ovary syndrome), rather than the ART. In contrast to the previous systematic review that suggested significant increase in cardiometabolic risk factors in ART offspring, the authors concluded that the cardiometabolic outcomes in ART children are, in general, reassuring. However, further studies with longer follow-up are needed.The study provided much-needed medium-term outcome data addressing this important question of long-term cardiometabolic risk in children born after ART. By combining high-quality Nordic registers, Norrman and colleagues have been able to create a uniquely large cohort of ART children in order to compare their risk of cardiovascular health with children born after SC. Such population-based design provided high coverage rate and high validity, such that missing data and the risk of selection bias can be minimized. However, there were some notable limitations of the study, including the relatively short follow-up period, especially among children born to ART. The number of clinical outcomes of interest was limited, hence restricting statistical power to detect differences in outcome. Although the use of national registries has minimized any risk of selection bias, the definitions of outcomes were based on inpatient and outpatient attendance and may be associated with some ascertainment bias, especially in relation to capturing obesity outcomes. There is also a significant proportion with missing maternal BMI, paternal characteristics, or other covariates, which posed limitations on the analyses. Another important point to note is that the impact of different ART factors on health of offspring has not been addressed. Over the years, ART practices and technologies have continued to evolve, for example, the increasing use of oocyte freezing and embryo biopsy for genetic testing and the shift of slow freezing to vitrification method for gamete or embryo freezing. It has been shown that singleton babies conceived from fresh embryo transfers of IVF are associated with increased risks of low birthweight and preterm delivery, while ART involving frozen embryos are associated with higher incidences of large babies, macrosomia, and hypertensive disorders of pregnancy [10]. Conversely, both low birthweight, intrauterine growth restriction (IUGR), as well as macrosomia have been linked with increased risk of later T2D and CVD [11]. These differential outcomes illustrate that the different ART techniques may have different safety profiles and exert different impacts on the long-term health of offspring. Of note, the study by Norrman and colleagues included relatively few births from frozen embryos, and these have not been compared to births by SC for later risk of diabetes or CVD.This important study highlights some of the challenges in ascertaining long-term effects of ART, or other early life exposures, for that matter. The establishment of ART registries including the important exposure factors may be an important component for the way forward, especially given the long-term follow-up required. There are important challenges, including those around confidentiality, but also the increasingly diverse and complex treatment protocols, as well as innovative technologies, which may be associated with different long-term outcomes. There is currently limited understanding of the long-term outcome of some of these novel techniques. There are also new challenges given the globalization of healthcare delivery, with increasing cross-border reproductive care [12]. The increasing cryopreservation of gametes, gonadal tissues, and embryos will pose new challenges on tracking the outcomes of ART births. More population-based long-term studies are warranted, and establishing the infrastructure that would facilitate anonymous linkage of ART registers, birth records with national diabetes and other disease registers that facilitate tracking of long-term health may be one way forward. Nevertheless, given the sensitivities around the data involved, such analyses may be difficult to perform in some areas, and population-based analyses, wherever possible, will continue to contribute much-needed data to this discussion.     

Determinants of current use of contraception and children ever born in Nepal

Abstract

This paper explores the extent to which women's work for earnings, education and couple communication over family planning influence current contraceptive use and children ever born in Nepal. Data came from the 1996 Nepal Family Health Survey. The findings indicate that education has a significant positive influence on current use of contraception and a significant negative influence on children ever born. There was virtually no relationship between women working and current use of contraception. However, in full models, there was a significant positive relationship for women who earn cash for work on current use and a significant negative relationship for children ever born. Working alone does not increase contraceptive use or reduce the number of children ever born in Nepal, but earning cash for work does. The husband/couple variables also proved to be important determinants of current use of contraception and children ever born.     

Defining smallness for gestational age in the early years of the Danish Medical Birth Registry

Background

Being born small for gestational age (SGA) is associated with decreased insulin sensitivity and increased blood pressure in childhood, but the association with clinical disease in early adulthood is less certain. The Danish Medical Birth Registry has registered all births in Denmark since 1973, but due to variable data quality, data is most often used only from 1981 onwards, and birth registers in other countries may have similar problems for the early years. We wanted to examine whether the data can be used for identification of children born SGA and used in future research.

Methodology/Principal Findings

All persons born between 1974 and 1996 were identified in the Danish Medical Birth Registry (n = 1.704.890). Immigrants and children without data on gestational age and birth weight were excluded, and a total of 1.348.106 children were included in the analysis. The difference between the different variables used in the history of the registry were examined, and the quality of data in the birth registry from 1974-1981 was examined and compared to subsequent years.Data on birth weight and gestational age in the early years of the registry is inconsistent, and the identification of children born SGA is inaccurate, with 49% false-positives. The biggest source of error is due to the rough and inaccurate intervals used for gestational age. By using –3 standard deviations as a cut-off for the identification of children born SGA, the number of false-positives was reduced to 9%, while the amount of false-negatives were increased.

Conclusion

Choosing –3 standard deviations for identifying children born SGA is a viable, though not optimal solution for identifying children born SGA. Overall the data in the registry is of sufficient quality to be used in further medical research.     

Health of human and livestock conceived by assisted reproduction.

Assisted reproduction is used to resolve infertility problems in human and in breeding programs to generate livestock. Except for gestation length and birth weight, perinatal outcome of children conceived by In Vitro Fertilization is similar to that of spontaneously conceived children. However, large offspring syndrome observed after In Vitro Production in livestock is quite alarming. The distinct parts of assisted reproduction (oocyte maturation, fertilization and culture) have been found to contribute to abnormal fetal growth and development. Genomic imprinting is suggested to be involved in the induction of the aberrant phenotypes observed after assisted reproduction. Furthermore, current knowledge on postnatal health of offspring conceived by assisted reproduction and speculations on potential longterm effects of In Vitro Fertilization will be described.     

Fertility Politics as "Social Viagra": Reproducing Boundaries, Social Cohesion, and Modernity in Italy

In this article, we investigate the delicacy of adopting pronatalism as a public position in Italy. Mounting scientific and political knowledge about the demographic "problem" exposes a new hegemonic formation that low fertility is dangerous. Drawing on ethnographic contexts, political debates, media publications, and policy documents, we trace the "demographic emergency" and compare two policies: a monetary baby bonus and a law restricting assisted reproduction. The coexistence of incentives to counter superlow fertility with prohibitions on high-tech baby making reflect the contested governance of "social cohesion." We conclude that scholarly and popular discourses serve as a sort of "social Viagra." Ultimately, both policies sought to rejuvenate family norms. Both aimed to fortify the political terrain of a nation-state struggling to achieve and maintain modernity against a backdrop of immigration and aging. Modernity became a weapon of the state to exert control over Italian fertility practices and of its critics to deploy orientalizing representations of backwardness.     

Orphaned at conception: the uncanny offspring of embryos

A number of advances in assisted reproduction have been greeted by the accusation that they would produce children 'without parents'. In this paper I will argue that while to date these accusations have been false, there is a limited but important sense in which they would be true of children born of a reproductive technology that is now on the horizon. If our genetic parents are those individuals from whom we have inherited 50% of our genes, then, unlike in any other reproductive scenario, children who were conceived from gametes derived from stem cell lines derived from discarded IVF embryos would have no genetic parents! This paper defends this claim and investigates its ethical implications. I argue that there are reasons to think that the creation of such embryos might be morally superior to the existing alternatives in an important set of circumstances.     

Desired family size, family planning and fertility in Ethiopia

This paper models the proximate determinants of children born to over 13,000 Ethiopian women and of the women's stated preferences for additional births using the data from the Ethiopian Demographic and Health Survey 2000. Empirical models for the number of children born to women were estimated using Poisson and ordinal regressions. The results show the importance of variables such as maternal education for smaller family size, and that variables reflecting desired family size are strong predictors of the numbers of children born to women. Secondly, binary logistic models for dichotomous variables for women not wanting more children and if getting pregnant would be a 'big problem' showed non-linear effects of the surviving and 'ideal' number of children. Moreover, the results indicated a desire on the part of women to limit family size, especially as the number of surviving children increased. Probit models were estimated to address potential endogeneity of certain variables. Overall, the results indicated that counselling couples about small family size and increasing the utilization of health care services can lower fertility in Ethiopia.     

Application of sperm sorting and associated reproductive technology for wildlife management and conservation

Efforts toward the conservation and captive breeding of wildlife can be enhanced by sperm sorting and associated reproductive technologies such as sperm cryopreservation and artificial insemination (AI). Sex ratio management is of particular significance to species which naturally exist in female-dominated social groups. A bias of the sex ratio towards females of these species will greatly assist in maintaining socially cohesive groups and minimizing male-male aggression. Another application of this technology potentially exists for endangered species, as the preferential production of females can enable propagation of those species at a faster rate. The particular assisted reproductive technology (ART) used in conjunction with sperm sorting for the production of offspring is largely determined by the quality and quantity of spermatozoa following sorting and preservation processes. Regardless of the ART selected, breeding decisions involving sex-sorted spermatozoa should be made in conjunction with appropriate genetic management. Zoological-based research on reproductive physiology and assisted reproduction, including sperm sorting, is being conducted on numerous terrestrial and marine mammals. The wildlife species for which the technology has undergone the most advance is the bottlenose dolphin. AI using sex-sorted fresh or frozen-thawed spermatozoa has become a valuable tool for the genetic and reproductive management of captive bottlenose dolphins with six pre-sexed calves, all of the predetermined sex born to date.     

Endocrine disrupters and testicular dysgenesis syndrome

Over the last couple of generations, we have been exposed to an increasing number of endocrine disrupters in our environment, including dichlorodiphenyltrichloroethane (DDT), PCB, certain pesticides, the phthalate DBP, synthetic steroids in meat and many other agents (table 1), which act as agonists or antagonists of sex steroids. Although biologists working with wildlife have been concerned about the possible effects of these chemical agents on animal reproduction, it appears that clinicians have been less concerned about possible health effects in humans. However, the increasing incidence of hormone-dependent cancers, including cancer of the breast, prostate and testis, and signs of an increasing incidence of male reproductive health problems should alert us to the possible association between exposure to endocrine disrupters and the current high frequency of reproductive problems. In Denmark, for example, 5% of all children are now born after assisted reproduction (intracytoplasmic sperm injection, in vitro fertilization, donor insemination and intrauterine insemination) and 1% of all (mostly young) men develop testicular cancer. Evidence exists to support the concept that hypospadias, undescended testis, poor semen quality and testicular cancer are symptoms of an underlying testicular dysgenesis syndrome, which may be becoming increasingly common due to adverse environmental effects. Experimental and epidemiological evidence suggests that testicular dysgenesis syndrome is a result of disruption of foetal programming and gonadal development during foetal life.     

The claim from adoption

In this article several justifications of what I call 'the claim from adoption' are examined. The claim from adoption is that, instead of expending resources on bringing new children into the world using reproductive technology and then caring for these children, we ought to devote these resources to the adoption and care of existing destitute children.
Arguments trading on the idea that resources should be directed to adoption instead of assisted reproduction because already existing people can benefit from such a use of resources whereas we cannot benefit individuals by bringing them into existence are rejected. It is then argued that a utilitarian argument proposed by Christian Munthe that supports the claim from adoption in some situations should be rejected because the support it offers does not extend to certain situations in which it seems morally obvious that resources should be expended on adoption rather than assisted reproduction. A version of the Priority View improves upon Munthe's utilitarianism by supporting the claim from adoption in the cases in which Munthe's argument failed. Some allegedly counterintuitive implications of the Priority View are then discussed, and it is concluded that the Priority View is more plausible than utilitarianism.
n a concluding section on policy issues it is argued that, even though the claim from adoption can be justified in a variety of situations, it does not follow that, in these situations, governments should direct resources away from assisted reproduction and towards adoption.     

The Spanish woman and birth control

The author presents in this article just a small part of the results obtained in national survey of 1.902 married women, carried out in 1972, on "fertility and family planning in Spain". More specifically, attitudes of this sample of Spanish married women towards family planning are explained. It is pointed out, in the first place, that eight out of every ten interviewed women say that all married couples who can have children ought to have them. Younger women and those with a higher socio-econimic status, however, are less in favor of that statement. Trough several questions it is also evident that the number of interviewees who think that other women control their fertility is higher the more distant from the respondent is the social circle about which the question is formulated. In other words, interviewees resist to admit that persons with whom they are more intimately related control their fertility. Approximately half the women in the sample say that married couples should have as many children as may come, but the other half say that couples should decide the number of children they want to have and when they want to have them. This last opinion is relatively more important among younger and higher status women. Along with the previous finding, almost half of the interviewees are very much in favor or rather in favor of family planning, that proportion being even higher among younger and higher status women. Finally, seven ou of every ten respondents say that there should be wide and complete information about all family planning methods, leaving it up to each individual to use or not to use them according to its own conscience. This opinion, of course, is also more common among younger and higher status women.     

Racial classification regarding semen donor selection in Brazil

Brazil has not yet approved legislation on assisted reproduction. For this reason, clinics, hospitals and semen banks active in the area follow Resolution 1358/92 of the Conselho Federal de Medicina, dated 30 September 1992. In respect to semen donation, the object of this article, the Resolution sets out that gamete donation shall be anonymous, that is, that the donor and recipients (and the children who might subsequently be born) shall not be informed of each other's identity. Thus, since recipients are unaware of the donor's identity, semen banks and the medical teams involved in assisted reproduction become the intermediaries in the process. The objective of this article is to show that, in practice, this represents disrespect for the ethical principles of autonomy, privacy and equality. The article also stresses that the problem is compounded by the racial question. In a country like Brazil, where racial classification is so flexible and goes side by side with racist attitudes, the intermediary role played by semen banks and medical teams is conditioned by their own criteria of racial classification, which are not always the same as those of donors and semen recipients. The data presented in this paper were taken from two semen banks located in the city of São Paulo (Brazil). At the time of my research, they were the only semen banks in the state of São Paulo and supplied semen to the capital (São Paulo city), the state of São Paulo, and to cities in other Brazilian states where semen banks were not available.     

Postnatal health and welfare of offspring conceived in vitro: a case for epidemiological studies

In vitro fertilization (IVF) has established itself as an important technique in human assisted reproduction and in livestock improvement. In both humans and livestock the possible long-term effects on health and welfare of offspring born after IVF and in vitro culture to the blastocyst stage are still largely unknown. Epidemiological studies in humans, using data collected for individuals born after normal (i.e. non-assisted) pregnancies, have provided evidence for associations between prenatal life events and adult-life disease. Due to the relatively short time that elapsed since the first IVF baby was born, comparable studies for IVF offspring are not yet possible. However, animal experiments and epidemiological studies with the available data from the livestock industry (mainly dairy cattle) may contribute to a better understanding of the risks involved.     

BIRTH‐ORDER DIFFERENCES CAN DRIVE NATURAL SELECTION ON AGING

Senescence—the deterioration of survival and reproductive capacity with increasing age—is generally held to be an evolutionary consequence of the declining strength of natural selection with increasing age. The diversity in rates of aging observed in nature suggests that the rate at which age‐specific selection weakens is determined by species‐specific ecological factors. We propose that, in iteroparous species, relationships between parental age, offspring birth order, and environment may affect selection on senescence. Later‐born siblings have, on average, older parents than do first borns. Offspring born to older parents may experience different environments in terms of family support or inherited resources, factors often mediated by competition from siblings. Thus, age‐specific selection on parents may change if the environment produces birth‐order related gradients in reproductive success. We use an age‐and‐stage structured population model to investigate the impact of sibling environmental inequality on the expected evolution of senescence. We show that accelerated senescence evolves when later‐born siblings are likely to experience an environment detrimental to lifetime reproduction. In general, sibling inequality is likely to be of particular importance for the evolution of senescence in species such as humans, where family interactions and resource inheritance have important roles in determining lifetime reproduction.     

R-Models: A mathematical framework for capturing notions of abstraction and assistance in reproductive systems

R-Models are an approach to capturing notions of assistance and abstraction in reproductive systems, based on labelled transition systems and Gibson's theory of affordances. R-Models incorporate a labelled transition system that describes how a reproductive system changes over the course of reproduction. The actors in the system are represented by a set of entities together with a relation describing the states in which those entities are present, and an affordance-modelling function mapping actions to sets of entities which enable those actions to be performed. We show how R-models can be classified based on whether the reproducer is assisted or unassisted in reproduction, and whether or not the reproducer is active during reproduction. We prove that all assisted and unassisted R-models have a related R-model which has the opposite classification. We discuss the relevance to the field of artificial life, give a potential application to the fields of computer virology, and demonstrate reproduction modelling and classification in action using examples.