Fertility Transition Research Articles

Establishment of new convenient two-line system for hybrid production by targeting mutation of OPR3 in allopolyploid Brassica napus

Abstract The two-line pollination control system, which usually depends on the utilization of thermosensitive or photoperiod genic male-sterile lines, has been widely used in various crops. However, this system is susceptible to instability issues caused by uncontrollable weather fluctuations. A stable and handy two-line pollination control system is highly desirable in many crop species for heterosis exploitation. Oxophytodienoic acid reductase 3 (OPR3) was proven to be involved in jasmonate biosynthesis. In the present study, CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeat) was utilized to mutate two OPR3 homologs in Brassica napus. After two OPR3 homologs were simultaneously mutated, mutants exhibited complete male sterility, and fertility could be easily restored by exogenous MeJA treatment. Hybrids produced from crosses between the opr3 sterile lines and normal varieties exhibited heterosis. This new two-line system based on OPR3 mutation provides higher stability and convenience than traditional systems. By using exogenous MeJA treatment to restore fertility, the system enables more precise control of male fertility transition, which has great potential to significantly contribute to the maneuverable production of hybrid seeds in rapeseed as well as other Brassica species crops.

Indigenous fertility in Aotearoa New Zealand: How does ethnic identity affect birth spacing and timing?

The survival of Indigenous peoples in the CANZUS states of Canada, Australia, Aotearoa New Zealand, and the United States is nothing short of remarkable. Not only have Indigenous peoples thwarted colonial tropes of the vanishing native but, for decades, Indigenous population growth rates have significantly outpaced those of the dominant settler populations. The future survival of Indigenous peoples fundamentally rests on continued natural increase, and understanding the causes and consequences of fertility behaviour is critical. While total fertility rates for Indigenous women in CANZUS countries are relatively low, childbearing tends to be concentrated at younger ages in contrast to the dominant white populations. The fertility transitions of both settler and Indigenous populations in the CANZUS states are well documented, however, a significant gap remains: how cultural factors shape contemporary Indigenous fertility behaviours. Using Aotearoa as a case study, we explore the relationship between Māori cultural identity, birth timing, and the duration of birth intervals. We use the 1995 New Zealand Women: Family, Employment and Education survey data to further test the impact of cultural identity on birth transition rates using the piecewise exponential model and Kaplan-Meier estimates. We find that women who identify MainlyMāori (exclusively or primarily) are at greater risk of bearing much earlier to first birth but not necessarily subsequent births. However, because of the earlier start, Māori have a longer reproductive window to bear more children, and at higher birth orders still bear earlier than non-Māori. The empirical evidence strengthens our case to suggest that cultural orientation has some influence on Indigenous fertility and contributes to the development of Indigenous-centred theories of fertility and demography more broadly.

China's family planning policy and fertility transition

Due to the immense population pressure and rapid population growth, the government of the People's Republic of China introduced the family planning policy in the 1950s and 1960s. It was fully implemented in the 1970s and tightened further into the one-child policy in the early 1980s. The implementation of the family planning policy played a significant role in China's fertility transition, with the total fertility rate shifting from approximately six to below the replacement level in around two decades. Facing the long-term low fertility rate and changes in the socioeconomic environment, the government implemented a selective two-child policy and a universal two-child policy in 2013 and 2015, respectively; consequently, the fertility rate rebounded temporarily. However, the two-child policy's effects have gradually diminished, and the fertility rate has declined dramatically since 2017. In 2021, China announced a three-child policy and supporting measures, followed by steps to improve the country's fertility support system, signifying a shift in China's family planning policy from a restrictive to an inclusive approach. Currently, there still exists potential for improvements in China's fertility level, and the key to tapping this potential lies in establishing a comprehensive, systematic, and sustainable fertility support policy system as soon as possible.

Changing fertility patterns in China

China's recent fertility data collected from the 2020 population census and 2017 fertility survey have considerably improved in quality. Based on these, we can assess the levels and patterns of fertility with high confidence. We reconstruct China's fertility history from 1990 using these two types of data and review the trends and characteristics of fertility transitions and changing fertility patterns in China. Over the past half century, China has experienced an extraordinary fertility transition and decline, which can be described as three stepwise downward jumps in fertility that occurred in the 1970s, 1990s, and 2010s. While the tempo effect has always depressed fertility, the quantum effect became positive in the most recent fertility decline, when China made successive adjustments to its fertility policy. Age, parity, and interval patterns of fertility in China have also undergone fundamental changes influenced by changing fertility policies and rapidly expanding higher education. The recent rapid decline in fertility is driven by the increasing postponement of marriage, a large reduction in fertility for lower education groups, and a rising proportion of younger women accessing higher education.

Fertility transition of Han and ethnic minorities in China: A tale of convergence and variation

China's large and diverse population exhibits interethnic variations in fertility, socioeconomic status, and culture. This study comprehensively analyzes data from multiple population censuses and qualitative interviews to identify fertility transition dynamics among ethnic groups in China. Taken together, the quantitative and qualitative results reveal a rapid decline in total fertility rates among both Han and ethnic minorities and a trend of convergence across different ethnic groups over the past few decades; in addition, the findings also show significant heterogeneity within ethnic minority populations. Our analysis sheds further light on the crucial role of social context and macro-level factors in shaping individuals’ reproductive behaviors. The results offer insights into how policies may address low fertility rates in China.

Perceived ideal number of children among adolescent girls in sub-Saharan Africa: does exposure to family planning messages matter?

BackgroundEven though evidence shows that fertility transition has begun almost everywhere in sub–Saharan Africa (SSA), the decline has been slower than in other parts of the world. Research shows that there is a positive relationship between fertility levels and fertility preference. Therefore, many countries in the region are implementing family planning education campaigns targeting at influencing reproductive behavior of women. Thus, this study aimed to examine the extent to which exposure to family planning communication influences fertility preferences of adolescent girls in SSA.MethodsThis study used data extracted from the most recent Demographic and Health Survey datasets for 28 countries in SSA. Analyses were conducted on a pooled sample of 87,950 female adolescents’ aged 15–19 years who were captured in respective country’s survey. Multivariable binary logistic regression model was fitted in Stata version 17 software to examine the association between exposure to family planning communication and fertility preference among adolescent girls in SSA.ResultsThe average fertility preference among adolescent girls in SSA was 4.6 children (95% CI: 4.5, 4.7). Findings show that regardless of the country, adolescents who had exposure to family planning messages [aOR = 0.76, 95% CI = 0.72–0.80] were less likely to prefer 4 or more children. On average, fertility preference among adolescents who had exposure to family planning communication was (3.8 children compared to 4.5 children; p < 0.001) among those with no exposure. Furthermore, results show that married adolescents in SSA who had exposure to family planning message had a higher average preferred family size compared to those who were not married (4.8 versus 3.8; p < 0.001).ConclusionExposure to family planning communication has shown the potential to influence adolescents’ fertility preference in sub-Saharan Africa. Adolescents with exposure to family planning messages preferred a small family size. Therefore, there is a need to scale-up family planning education programmes in order to reduce fertility further in SSA.

Missions, fertility transition, and the reversal of fortunes: evidence from border discontinuities in the emirates of Nigeria

Missions, fertility transition, and the reversal of fortunes: evidence from border discontinuities in the emirates of Nigeria

Exploring how unemployment and grandparental support influence reproductive decisions in sub-Saharan African countries: Nigeria in focus

The socioeconomic factors driving the adoption of birth limitation and lengthening birth intervals as fertility control mechanisms in sub-Saharan Africa are a subject of debate. There are also arguments over what accounts for the low performance of the adopted fertility control mechanisms, and the break experienced in the fertility transition process. To fill the gaps, the authors work from a life-course perspective and linked data from the National Bureau of Statistics and the National Population Commission to collect retrospective data from 416 participants. Drawing on the socioeconomic framework, the roles of unemployment and grandparental support in reproductive decisions were tested. Results suggest that the unemployment situation is an underlying mechanism that triggered the adoption of birth control measures in Nigeria. The results also suggest that grandparental support accounts for the slow pace of the fertility transition process. This current study concludes that the unemployment situation pressures parents to reduce the number of childbirth. However, where grandparental support for grandchildren is available, parents tend to have a large family size in line with the pro-natalist nature of Nigerians.

Sustained and Universal Fertility Recuperation in Kazakhstan

The fertility rates of Kazakhstan have reversed to levels not seen for several decades. The striking fertility increase poses questions regarding the extent to which this new development is shared across socio-demographic groups and the nature of fertility recuperation. The current study employs UNICEF Multiple Indicator Cluster Survey data and event-history modelling to analyse parity progressions to one, two, three, and four children. The results suggest a sustained fertility increase that is not merely associated with the recuperation of delayed first births, but a genuine increase across all birth orders. This pattern is evident for both main ethnicities in Kazakhstan and across educational groups. The gradual increase of higher-order births, especially among ethnic Kazakhs, indicates a reversed fertility transition and also that the previous fertility decline in the 1990s was not part of a general transition towards below-replacement fertility but rather a reflection of economic crisis after the collapse of the Soviet Union.

Child survival and contraception choice: Theory and evidence

This paper asks whether increases in child survival bring down fertility and incentivize couples to switch from traditional to modern methods of contraception. Our parsimonious model predicts the answer in each case is, yes. We test these connections using household-level Demographic and Health Surveys from recent fertility transitions using arguably exogenous variation in child survival at the regional level. We find a 1% increase in ambient child survival leads to a fertility drop of 1.2%. The same raises the chance of switching to modern birth control (and sticking to it) by 0.4%. Our finding supports the notion that prevailing rates of child survival influence the effectiveness of family planning programs that promote modern contraceptive use.

How Can African Countries Address Climate Change Problems and Optimise Demographic Dividends for Socioeconomic Development?

As all 54 countries in Africa strive to overcome their different socio-economic challenges, the climate crisis as well as the unsustainable population growth appear to be threatening the attainment of national and international development agenda across the continent. This paper presents the relationship between climate change and population dynamics; how Africa can address the problems of the climate crisis and rapid population growth, and create the potential to harness a demographic dividend and accelerate economic growth. Many African countries need to take necessary measures to achieve a rapid and sustained fertility transition, including providing access to quality family planning services, reducing adolescent fertility, educating female children, empowering women, reducing under-five mortality and expanding labour market opportunities. These are necessary conditions for fertility transition and reaping the benefit of a demographic dividend in Africa. As African countries take strategic steps to catalyse fertility transition and accelerate economic growth, there is a need to take urgent measures to fight the climate change crisis which appears to be eroding socio-economic gains across the continent. While Africa adds only a trifling fraction of the global greenhouse gas emissions, the continent bears a disproportionately significant portion of the detrimental impact of climate change. Without the necessary actions to stem and reverse the consequences (such as health crises, food insecurity due to the destruction of crops by severe weather, the destruction of livelihoods and increases in the numbers of internally displaced persons), climate change is likely to have significant negative effects on the achievement of the sustainable development goals and the African Union’s Agenda 2063. There is a need to address the twin problems of unsustainable population growth and climate crisis in Africa.

Near-universal marriage, early childbearing, and low fertility: India's alternative fertility transition.

To compare fertility in India to both low-to-middle-income and high-income countries (LMICs and HICs) and describe the patterns that have accompanied India's transition to low fertility. We use data from the Demographic and Health Surveys (DHS), the United Nations (UN), and the Organisation for Economic Co-operation and Development (OECD) to observe factors associated with fertility decline in 36 Indian states and 76 countries. Although fertility in India has declined to levels similar to HICs, women's entry into marriage and initiation of childbearing are more in line with patterns found in LMICs. The vast majority of women in India (97%) are married by age 30, and their average age at first birth is only 21.3 years old. In spite of these patterns, average fertility has declined in India as a result of earlier termination of childbearing. Among more recent cohorts, fewer women progressed to higher-order births and about half of women obtained a sterilization by age 35. India has reached low fertility by mechanisms outside the traditional indicators of fertility decline. In contrast to countries that have achieved low fertility through delayed age at first birth, women in India have continued to enter unions and bear children early, lowered their age at last birth, and increasingly ended their fertility via sterilization following the birth of two children. Evidence from India reveals an alternative pathway to low fertility, highlighting the limitations of traditional socioeconomic indicators for explaining fertility decline.

Childbearing Trajectories in a West African Setting: A Sequence Analysis Approach

The lagging fertility transition in West Africa has important repercussions for global population growth but remains poorly understood. Inspired by Caldwell and colleagues' fertility transition framework, as well as by subsequent research, we examine diversity in women's holistic childbearing trajectories in Niakhar, Senegal, between the early 1960s and 2018 using a sequence analysis approach. We evaluate the prevalence of different trajectories, their contribution to overall fertility levels, and their association with women's socioeconomic and cultural characteristics. Four trajectories were observed: “high fertility,” “delayed entry,” “truncated,” and “short.” While the high fertility trajectory was most prevalent across cohorts, delayed entry grew in importance. The high fertility trajectory was more common among women born between 1960 and 1969 and was followed less often by divorced women and those from polygynous households. Women with primary education and those from higher status groups were more likely to experience delayed entry. The truncated trajectory was associated with lack of economic wealth, polygynous households, and caste membership. A short trajectory was related to lack of agropastoral wealth, divorce, and possibly secondary sterility. Our study advances knowledge on fertility transitions in Niakhar—and Sahelian West African contexts more generally—by showing the diversity of childbearing trajectories within high fertility regional contexts.

Moving Closer for the Grandchild? Fertility and the Geographical Proximity of a Mother and Her Adult Daughter in a Dynamic Perspective

Recent research has analyzed how the geographical distance between mothers and adult daughters influenced the daughters' fertility transitions. The inverse relationship has received less attention: that is, whether a daughter's fertility—her pregnancies and the ages and number of her children—is affected by her geographical proximity to her mother. The current study helps to close this gap by considering moves by either adult daughters or mothers that lead them to live nearby again. We use Belgian register data on a cohort of 16,742 firstborn girls aged 15 at the beginning of 1991 and their mothers who lived apart at least once during the observed period (1991–2015). Estimating event-history models for recurrent events, we analyzed whether an adult daughter's pregnancies and the ages and number of her children affected the likelihood that she was again living close to her mother and, if so, whether the daughter's or the mother's move enabled this close living arrangement. The results show that daughters were more likely to move closer to their mothers during their first pregnancy and that mothers were more likely to move closer to their daughters when the daughters' children were older than 2.5 years. This study contributes to the growing literature investigating how family ties shape (im)mobility.

Fertility Transition in Brazilian Municipalities: An Exploratory Analysis of Cross-sectional Data in 1991, 2000 and 2010

Understanding the fertility transition in Brazil at the municipal scale provides important support for designing and implementing local policies that incorporate spatial heterogeneity into local sociodemographic dimensions. To analyze the heterogeneity of the fertility transition process among Brazilian municipalities over the last two decades, we rewrite the logistic curve equation, estimate the parameters of the national logistic curve and allocate Brazilian municipalities in the national trend using their own total fertility rates. The lag between most and least developed areas persists in either the North or Northeast Region, opposite to what is observed in the South and Southeast. While some municipalities are beyond their time regarding the national average fertility transition, others are at the beginning of the transition. The very fast fertility decline experienced by late runners in the more recent period results in changes in age composition, configuring a challenge that social decision-makers should face.

Spillovers in Childbearing Decisions and Fertility Transitions: Evidence from China

Abstract This article uses China’s family planning policies to quantify and explain spillovers in fertility decisions. We test whether ethnic minorities decreased their fertility in response to the policies, although only the majority ethnic group, the Han Chinese, were subject to birth quotas. We exploit the policy rollout and variation in pre-policy age-specific fertility levels to construct a measure of the negative shock to Han fertility. Combining this measure with variation in the local share of Han, we estimate that a woman gives birth to 0.63 fewer children if the average completed fertility among her peers is exogenously reduced by one child. The fertility response of minorities is driven by cultural proximity with the Han and by higher educational investments, suggesting that spillovers operate through both social and economic channels. These results provide evidence that social multipliers can accelerate fertility transitions.

Union formation, within-couple dynamics, and child well-being: A global macrolevel perspective.

Studies on global changes in families have greatly increased over the past decade, adopting both a country-specific and, more recently, a cross-national comparative perspective. While most studies are focused on the drivers of global changes in families, little comparative research has explored the implications of family processes for the health and well-being of children. This study aims to fill this gap and launch a new research agenda exploring the intergenerational implications of union-formation and within-couple dynamics for children's health and well-being across low- and middle-income countries (LMICs), both globally, regionally, and by the stage of fertility transition. We do so by adopting a macro-level perspective and a multi-axis conceptualization of children's outcomes - health at birth, health in later life, and schooling - and leveraging Demographic and Health Survey and World Bank data across 75 LMICs. Our results show that in societies where partnerships are characterized by more equal status between spouses - i.e., where the age range between spouses and differences in years of schooling between partners are narrower - children fare better on several outcomes. These associations are particularly strong in mid- and high-fertility settings. Despite a series of regularities, our results also highlight a set of findings whereby, at a macro-level, the prevalence of marriage and divorce/separation are not invariably associated with children's outcomes, especially in LMICs where fertility is comparatively lower. We document little cross-regional heterogeneity, primarily highlighting the centrality of demographic factors such as age vis-à-vis, for instance, region-specific characteristics that are more tied to the social fabric of specific societies.

The scientific revolution and its implications for long-run economic development

We analyze the role of the Scientific Revolution in the takeoff to sustained long-run economic development. Basic scientific knowledge is a necessary input in the production of applied knowledge, which, in turn, fuels productivity growth and leads to rising incomes. Subsequently, rising incomes instigate a fertility transition and foster education investments. Together, the increasing stocks of basic scientific knowledge and human capital, and the concomitant reduction in fertility enable economic development. In regions where scientific inquiry is severely constrained—for example, due to religious reasons or due to oppressive rulers—the takeoff is delayed or may not occur at all. This shows the importance of investing in basic scientific inquiry when trying to achieve long-run economic prosperity. Our framework could contribute to the understanding of why sustained economic development emerged first in Europe and not in technologically more advanced China.

Naming the Precious Child: New Evidence of Intentional Family Planning in Historical Populations

Can the names parents gave their children give us insights into how parents in historical times planned their families? In this study, we explore whether the names given to the firstborn child can be used as indicators of family-size preferences and, if so, what this reveals about the emergence of intentional family planning over the course of the demographic transition. We analyze historical populations from 1850 to 1940 in the United States, where early fertility control and large sample sizes allow separate analyses of the White and Black populations. We also analyze Norway from 1800 to 1910, where there was a much later fertility transition. A split-sample method allows automated scoring of each name in terms of predicted family size. We find a strong relationship between naming and family size in the U.S. White population as early as 1850, for the Black population beginning in 1940, and for the Norwegian population in 1910. These results provide new evidence of the emergence of “conscious calculation” during the fertility transition. Our methods may also be applicable to modern high-fertility populations in the midst of fertility decline.

Determinants of Fertility During the Fertility Transition in Estonia: A Spatial Analysis

Determinants of Fertility During the Fertility Transition in Estonia: A Spatial Analysis