By Jensen Clark, DO
Editor’s Note: Jensen Clark, DO, a first-year anesthesiology resident at the University of New Mexico, wrote this research review after completing the FACTS elective during her fourth year of medical school. She examined the study by Kulu et al., which found that Britain’s declining fertility rates over the past three decades have been driven primarily by delayed first births rather than a reduced desire for children. As women increasingly postpone childbearing, Dr. Clark highlights the important relationship between fertility awareness-based methods (FABMs), age-related fertility decline, and reproductive health and emphasizes the value of fertility education in helping patients make informed decisions about family planning and understanding the impact of reproductive timing on future reproductive outcomes.
Introduction
Over the past three decades, fertility patterns in Britain have changed significantly.[1] After a modest rise in fertility during the early 2000s, rates declined sharply in the 2010s, reaching historically low levels.[2] [3] [4] [5] [6] This has often been explained by pointing to economic uncertainty, but other factors—such as social norms, education, and policy changes—have also been implicated.
“Over the past three decades, fertility patterns in Britain have changed significantly … (as) rates declined sharply in the 2010s, reaching historically low levels.”
This study seeks to provide a more precise understanding of the fertility trends in Britain by evaluating long-term data and childbearing patterns by birth order, also known as parity. Rather than relying solely on aggregate measures like total fertility rate (TFR), the authors investigate how first, second, and higher-order births contribute to overall trends. Additionally, the study compares patterns between England, Wales, and Scotland and evaluates the role of population characteristics, such as education and ethnicity. This approach allows for a deeper understanding of factors driving fertility changes.
Methodology
The study utilizes longitudinal population data from two large datasets: the Office for National Statistics Longitudinal Study (ONS LS) for England and Wales and the Scottish Longitudinal Study (SLS).[1] These datasets provide detailed fertility histories, allowing for analyses across multiple decades.
The authors employed hazard regression models (a form of survival analysis) to calculate parity-specific fertility rates. These models account for factors such as age and time since previous birth, enabling differentiation between changes in timing (tempo) and total number of children (quantum).[7] [8] [9]
The sample included women born in 1956 or later and tracked their fertility from adolescence through their reproductive years. Analyses were conducted separately for first, second, third, and fourth births. Additional stratification by education level and ethnicity allowed assessment of population composition.
Overall, the methodology is robust, leveraging large-scale longitudinal data and advanced statistical modeling to provide a nuanced picture of fertility dynamics.
Results
The findings reveal several key patterns. Most importantly, first births are the primary driver of fertility trends. First-birth rates declined in the 1990s, increased in the 2000s, and declined again in the 2010s. This pattern closely mirrors overall TFR trends. Importantly, these changes are largely explained by delayed childbearing, rather than a significant increase in permanent childlessness. The average age at first birth rose from approximately 28 years in the early 1990s to over 31 years by 2017.[1]
Second- and third-birth rates show a different pattern. While these declined in the 1990s, they remained relatively stable or slightly increased after 2000.[1] Notably, birth intervals between children did not significantly change, suggesting that women are not spacing children further apart but are instead starting families later.
Third, Scotland consistently exhibits lower fertility than England and Wales [1], primarily due to lower rates of second and third births rather than differences in first births or timing.
Finally, population composition, including education and ethnicity, only had a minor impact on overall fertility trends. While subgroup differences do exist, such as higher second-birth rates among highly educated women and higher third-birth rates among ethnic minorities, these factors do not substantially explain national fertility changes.
Discussion
This study provides important insights into fertility behavior that are highly relevant to women’s health and family planning. One of the most significant findings is that delayed initiation of childbearing is the dominant factor driving fertility decline, rather than a widespread decision to have fewer children. This has direct implications for fertility awareness-based methods (FABMs) and reproductive counseling. As women delay childbearing into their 30s, the biological window for optimal fertility narrows, thereby increasing the risk of subfertility and involuntary childlessness.
“One of the most significant findings is that delayed initiation of childbearing is the dominant factor driving fertility decline, rather than a widespread decision to have fewer children.”
From a clinical perspective, this reinforces the importance of patient education. This is necessary for many topics, including age-related fertility decline. As the medical field advances, many patients may assume that delayed childbearing can be easily compensated for later, which is not necessarily the case. This study suggests that while higher-order births remain relatively stable, the opportunity to begin childbearing may become increasingly constrained.
Another key takeaway is the emergence of a new reproductive pattern: later first births without a significant reduction in subsequent births. This suggests that once women begin having children, they remain motivated to achieve their desired family size. However, this pattern may not be sustainable long-term, as continued postponement could eventually limit the ability to have multiple children due to declining fecundity.
“Another key takeaway is … once women begin having children, they remain motivated to achieve their desired family size. However, this pattern may not be sustainable long-term, as continued postponement could … limit the …(number of) children due to declining fecundity.”
The study also highlights socioeconomic disparities. The decline in first births among younger, less-educated women in the 2010s suggests that economic instability may disproportionately affect vulnerable populations. This aligns with broader evidence linking financial insecurity to delayed family formation. In addition to patient education, there is room for improvement from a public health standpoint, including policies that support reproductive decision-making, access to childcare, parental leave, and economic stability.
Strengths and Limitations
A major strength of this study is its use of large, longitudinal datasets, enabling detailed and reliable analyses of fertility patterns over time. The parity-specific approach provides insights that would be missed using aggregate measures alone. Additionally, the comparison between similar yet distinct populations (England & Wales vs Scotland) strengthens the validity of the findings.
However, there are limitations. The data only extend to 2017, and therefore, do not capture more recent fertility trends like the impact of the COVID-19 pandemic. Additionally, while the study identifies patterns, it cannot definitively establish causation. Factors such as cultural norms, personal preferences, and policy changes are complex and not fully captured in the analysis.
Insights and Future Directions
This study raises important questions about the future of fertility trends. If postponement of first births continues, will this eventually lead to increased childlessness or reduced family size? Additionally, how will advancements in reproductive technology influence these patterns?
From a fertility-awareness perspective, there is a clear need for improved education regarding reproductive timing. Many individuals may benefit from greater access and earlier counseling about fertility potential and limitations. Furthermore, future research should explore how social, economic, and psychological factors interact to influence reproductive decision-making. It is worth evaluating how access to FABM education and family planning through this lens impacts family-planning outcomes and fertility trends in the coming decades.
“From a fertility awareness perspective, there is a clear need for improved education regarding reproductive timing.”
Another important area for future studies is the long-term impact of delayed childbearing on maternal and child health outcomes. As the average age at first birth continues to rise, understanding associated risks will be critical for clinical practice.
Conclusion
In summary, this study demonstrates that changes in fertility in Britain over the past three decades are primarily driven by delayed first births rather than reductions in desired family size. While higher-order births remain relatively stable, continued postponement may have long-term consequences for fertility outcomes. These findings are highly relevant to women’s health and highlight the importance of integrating fertility awareness into clinical care and public health strategies.
REFERENCES
[1] Kulu, H., Kuang, B., Christison, S., & Berrington, A. (2026). Long-term fertility trends by birth order in Britain: Comparison between England & Wales and Scotland. Population Studies , 80 (1), 1–23. https://doi.org/10.1080/00324728.2025.2491354
[2] Hellstrand, Julia, Jessica Nisén, and Mikko Myrskylä. 2020. All-time low period fertility in Finland: Demographic drivers, tempo effects, and cohort implications, Population Studies 74(3): 315–329. Crossref. PubMed. Web of Science.
[3] Ermisch, John. 2021. English fertility heads south: Understanding the recent decline, Demographic Research 45: 903–916. Crossref. Web of Science.
[4] Ermisch, John. 2024. The recent decline in period fertility in England and Wales: Differences associated with family background and intergenerational educational mobility, Population Studies 78(2): 325–339. Crossref. PubMed. Web of Science.
[5] Berrington, Ann, Joanne Ellison, Bernice Kuang, Sindhu Vasireddy, and Hill Kulu. 2022. Scenario-based fertility projections incorporating impacts of COVID-19, Population, Space and Place 28(2). Crossref. Web of Science.
[6] Ohlsson-Wijk, Sofi, and Gunnar Andersson. 2022. Disentangling the Swedish fertility decline of the 2010s, Demographic Research 47: 345–358. Crossref. Web of Science.
[7] Hoem, J. M. 1990. Social policy and recent fertility change in Sweden, Population and Development Review 16(4): 735. Crossref. Web of Science.
[8] Andersson, Gunnar. 1999. Childbearing trends in Sweden 1961-1997, European Journal of Population/ Revue europenne de demographie 15(1): 1–24. Crossref. PubMed. Web of Science.
[9] Kulu, Hill, and Tina Hannemann. 2016. Why does fertility remain high among certain UK-born ethnic minority women?, Demographic Research 35(1): 1441–1488. Crossref.
ABOUT THE AUTHOR
Jensen Clark, DO , is a first-year Anesthesiology resident at the University of New Mexico. She earned her Doctor of Osteopathic Medicine from Rowan-Virtua School of Osteopathic Medicine in Stratford, New Jersey, after completing her undergraduate education at the University of Hawaiʻi at Mānoa in Honolulu. Her professional interests include health equity, medical education, and advancing patient-centered care.
Dr. Clark participated in the FACTS elective because she recognized that many medical students graduate with significant knowledge gaps in fertility awareness-based methods and reproductive health topics. She was eager to deepen her understanding of these areas before beginning residency training.
Although she may have fewer opportunities to discuss these topics routinely in anesthesiology practice, Dr. Clark believes there are meaningful ways to incorporate reproductive health conversations into patient care. She is committed to ensuring that patients feel informed, empowered, and supported in making decisions about their reproductive health.
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