Temporal Trends in Fertility Rates: A Nationwide Registry Based Study from 1901 to 2014

Longitudinal trends in fertility in women of advanced maternal age in the United States and Sweden from 1935-2018 and comparison to maternal mortality ratios

Advanced maternal age (AMA, >35 years at delivery) confers maternal and foetal risks, particularly with age >45 years and nulliparity, but longitudinal comparative data on age- and parity-specific AMA fertility is lacking. We used the Human Fertility Database (HFD), a publicly available, international database, to analyse fertility in US and Swedish women aged 35-54 from 1935 to 2018. Age-specific fertility rates (ASFR), total birth counts, and proportion of AMA births were evaluated across maternal age, parity, and time, and compared to maternal mortality rates during the same time. In the US, total AMA births nadired in the 1970s, and have risen since. Until 1980, most AMA births were to women completing parity 5 or higher; since then, most have been to low parity women. While ASFR in 35 to 39 year olds was highest in 2015, ASFR in women 40-44 and 45-49 were highest in 1935, though they have been rising recently, especially in low-parity women. While the same AMA fertility trends were seen in the US and Sweden from 1970-2018, maternal mortality rates have risen in the US despite remaining low in Sweden. Although AMA is known to contribute to maternal mortality, this discrepancy merits further consideration.

Fertility Intention and Related Factors for Having a Second or Third Child Among Childbearing Couples in Shanghai, China

Background and Purpose

As the global fertility rate declines, China has issued two and three-child policies in the past 10 years. Therefore, this study serves to evaluate fertility intention rates and related factors in couples intending to have a second child and third child.

Methods

A cross-sectional survey was conducted in mainland China from July to August 2021. Couples with one or two children were invited to participate in our study in order to collect information about more than one child fertility intention and the possibly related factors. Odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were calculated and adjusted for potential confounding factors.

Results

Data was collected from a total of 1,026 couples. Among couples with one child, 130 (16.2%) couples had the intention to have a second child. Additionally, only 9.4% of couples with two children desired to have third child. The study revealed large differences in socioeconomic and personal factors between the two groups. For couples with intentions for a second-child, a female age >35 years (adjusted odds ratio, aOR 1.92), a first child's age range from 3 to 6 (aOR 3.12), annual child spending as a percentage of household income >30% (aOR 2.62), and children's educational barriers (aOR 1.55) were associated with lack of intent to have a second child. Similarly, among couples with two children, parents with family financial constraints (aOR 6.18) and children's educational barriers (aOR 4.93) are more likely to have lack of intent to have a third child. Here, we report that government policies encouraging fertility (aOR 0.04) can effectly promote couples to pursue a second or third child.

Conclusion

Overall, couples with one or two children in Shanghai had a low intention to give birth to a second or third child. In order to increase the birth rates, it is necessary to implement policies to reduce the burden of raising children and provide relief to parent's pressure of rearing a child with increased free time.

Association of pregnancies with risk of multiple sclerosis

Background:

Pregnancies have an impact on the disease course of multiple sclerosis (MS), but their relationship with MS risk is yet unclear.

Objective:

To determine the relationships of pregnancies and gynecological diagnoses with MS risk.

Methods:

In this retrospective case–control study, we assessed differences in gynecological International Classification of Diseases, 10th Revision (ICD-10) code recording rates between women with MS (n = 5720), Crohn’s disease (n = 6280), or psoriasis (n = 40,555) and women without these autoimmune diseases (n = 26,729) in the 5 years before diagnosis.

Results:

Twenty-eight ICD-10 codes were recorded less frequently for women with MS as compared to women without autoimmune disease, 18 of which are pregnancy-related. After adjustment for pregnancies, all codes unrelated to pregnancies were still negatively associated with MS. In a sensitivity analysis excluding women with evidence for possible demyelinating events before diagnosis, all associations were more pronounced. In comparison to women with psoriasis, most associations could be confirmed; that was not true in comparison to women with Crohn’s disease.

Conclusion:

Our findings provide evidence for a possible protective effect of pregnancies on MS risk likely independent of or in addition to a previously suggested reversed causality. The negative associations of gynecological disorders with disease risk need further investigation. The associations might be shared by different autoimmune diseases.

The impact of early pregnancy complications on completed family size-A nationwide, registry-based cohort study with 40 years of data

INTRODUCTION

The impact of early pregnancy complications on completed family size is unknown. Here, we hypothesize that early pregnancy complications and adverse outcomes may influence family size.

MATERIAL AND METHODS

In this nationwide, registry-based study we included all 458 475 women born 1957-1972 who lived in Denmark from age 20-45 years with at least one registered pregnancy. The main outcome of the study was number of children per woman by age 45, estimated using a Generalized Linear Mixed Model. Exposures were: (a) total number of pregnancy losses experienced (0, 1, 2, ≥3); (b) highest number of consecutive pregnancy losses (0, 1, 2, ≥3); (c) sex of firstborn child; (d) outcome of first pregnancy (live birth, stillbirth, pregnancy loss, ectopic pregnancy, or molar pregnancy).

RESULTS

Number of live births was negatively influenced by maternal age and adverse first pregnancy outcomes, especially ectopic pregnancies. A 30-year-old woman with a first ectopic pregnancy was expected to have 1.16 children (95% CI 1.11-1.22) compared with 1.95 children (95% CI 1.86-2.03) with a first live birth. Three or more consecutive losses also decreased number of live births significantly: 1.57 (95% CI 1.50-1.65) compared with 1.92 (95% CI 1.84-2.0) with only live births. The total number of pregnancy losses had no effect before the age of 35 years. Sex of firstborn had no effect.

CONCLUSIONS

Previous pregnancy history has a significant effect on number of children per woman, which is important at both individual and societal levels. Pathophysiological research of adverse pregnancy outcomes should be an urgent priority as the causes remain poorly understood.

Parenthood Rates and Use of Assisted Reproductive Techniques in Younger Hodgkin Lymphoma Survivors: A Danish Population-Based Study

PURPOSE

The majority of young adults with Hodgkin lymphoma (HL) are cured, but chemotherapy-induced infertility can have profound psychosocial consequences. Providing data on parenthood rates and use of assisted reproductive techniques (ARTs) after contemporary HL treatment is important for patient counseling and survivorship care.

MATERIALS AND METHODS

All Danish patients with HL diagnosed during 2000-2015 at the ages 18-40 years who achieved remission after first-line therapy were included and matched on age, sex, and parenthood status to five random persons from the general population. Parenthood rates were defined as the rate of first live birth per 1,000 person years, starting 9 months after HL diagnosis. Nationwide birth and patient registers were used to capture parenthood outcomes and ARTs use.

RESULTS

A total of 793 HL survivors and 3,965 comparators were included (median follow-up 8.7 years). Similar parenthood rates were observed for male and female HL survivors when compared with matched comparators (56.2 v 57.1; P = .871 for males and 63.8 v 61.2; P = .672 for females). For male HL survivors, BEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone) therapy was associated with lower parenthood rates as compared to the matched comparators (28.1 v 60.8; P = .020). Live birth after ARTs were more common for HL survivors than for comparators (males 21.6% v 6.3%; P < .001; females 13.6% v 5.5%; P = .001). There were no differences in gestational age, Apgar score, or newborn measurements between HL survivors and matched comparators.

CONCLUSION

The parenthood rates for HL survivors who have not experienced relapse were generally similar to the general population. However, ARTs were used more often before the first live birth in HL survivors, which is relevant information when discussing possible long-term side effects and fertility-preserving treatment options.

Fertility rates and the postponement of first births: a descriptive study with Finnish population data

OBJECTIVES

We described the trend of fertility rates, age-specific fertility rates and associated factors in Finland over a 30-year period.

DESIGN

A descriptive population-based register study.

SETTING

Fertility data, including age at first birth, childlessness and educational levels were gathered from the Finnish Medical Birth Register and Statistics Finland.

PARTICIPANTS

All 1 792 792 live births from 1987 to 2016 in Finland.

MAIN OUTCOME MEASURES

Completed fertility rate, total fertility rate and age-specific fertility rate.

RESULTS

The total fertility rate of Finnish women fluctuated substantially from 1987 to 2016. Since 2010, the total fertility rate has gradually declined and reached the lowest during the study period in 2016: 1.57 children per woman. The mean maternal age at first birth rose by 2.5 years from 26.5 years in 1987 to 29 years in 2016. The proportion of childless women at the age of 50 years increased from 13.6% in 1989 to 19.6% in 2016. By considering the impact of postponement and childlessness, the effect on total fertility rates was between -0.01 and -0.12 points. Since 1987, the distribution of birth has declined for women under the age of 29 and increased for women aged 30 or more. However, start of childbearing after the age of 30 years was related to the completed fertility rate of less than two children per woman. The difference in completed fertility rate across educational groups was small.

CONCLUSIONS

Postponement of first births was followed by decline in completed fertility rate. Increasing rate of childlessness, besides the mean age at first birth, was an important determinant for declined fertility rates, but the relation between women's educational levels and the completed fertility rate was relatively weak.

Use of assisted reproductive technologies before and after the Artificial Reproduction Act in Taiwan

Background

Low birth rates and infertility are growing concerns for many countries. The Artificial Reproduction Act (ARA) was implemented in 2007 to better support the use of assisted reproductive technology (ART) in Taiwan. This study aims to examine trends in the use of ART and to determine impacts of the ARA on ART use.

Method

This study used data from the Health Promotion Administration in Taiwan. We used auto-regression models to examine the recent trends (1998–2017) in fertility related indicators and the use of ART. An interrupted time series design and segmented linear regression models were applied to analyze the changes in number of ART treatment cycles and birth rates by ART following the ARA.

Results

The number of births by ART has gradually increased, with an annual growth rate of 21.55%. The rate of births by ART increased from 0.86% in 1998 to 1.44% in 2007, and to 4.33% in 2016 (annual growth rate: 41.23%). We estimated a relative increase of 78.51% (95%CI: 46.13%, 110.90%) in the number of births by ART and a relative increase of 35.67% (95%CI: 18.87%, 52.47%) in rate of births by ART 5 years following the ARA was implemented.

Conclusion

ART has been seen as an approach to improve fertility. Our analysis suggests that the ART use and births associated from ART use both increased in Taiwan following the implementation of ARA. This experience in Taiwan may offer important lessons for other countries that are facing low fertility challenges.

Complex genetics of female fertility

Variation in reproductive lifespan and female fertility have implications for health, population size and ageing. Fertility declines well before general signs of menopause and is also adversely affected by common reproductive diseases, including polycystic ovarian syndrome (PCOS) and endometriosis. Understanding the factors that regulate the timing of puberty and menopause, and the relationships with fertility are important for individuals and for policy. Substantial genetic variation exists for common traits associated with reproductive lifespan and for common diseases influencing female fertility. Genetic studies have identified mutations in genes contributing to disorders of reproduction, and in the last ten years, genome-wide association studies (GWAS) have transformed our understanding of common genetic contributions to these complex traits and diseases. These studies have made great progress towards understanding the genetic factors contributing to variation in traits and diseases influencing female fertility. The data emerging from GWAS demonstrate the utility of genetics to explain epidemiological observations, revealing shared biological pathways linking puberty timing, fertility, reproductive ageing and health outcomes. Many variants implicate DNA damage/repair genes in variation in the age at menopause with implications for follicle health and ageing. In addition to the discovery of individual genes and pathways, the increasingly powerful studies on common genetic risk factors help interpret the underlying relationships and direction of causation in the regulation of reproductive lifespan, fertility and related traits.

Older fathers' children have lower evolutionary fitness across four centuries and in four populations

Higher paternal age at offspring conception increases de novo genetic mutations. Based on evolutionary genetic theory we predicted older fathers' children, all else equal, would be less likely to survive and reproduce, i.e. have lower fitness. In sibling control studies, we find support for negative paternal age effects on offspring survival and reproductive success across four large populations with an aggregate N > 1.4 million. Three populations were pre-industrial (1670-1850) Western populations and showed negative paternal age effects on infant survival and offspring reproductive success. In twentieth-century Sweden, we found minuscule paternal age effects on survival, but found negative effects on reproductive success. Effects survived tests for key competing explanations, including maternal age and parental loss, but effects varied widely over different plausible model specifications and some competing explanations such as diminishing paternal investment and epigenetic mutations could not be tested. We can use our findings to aid in predicting the effect increasingly older parents in today's society will have on their children's survival and reproductive success. To the extent that we succeeded in isolating a mutation-driven effect of paternal age, our results can be understood to show that de novo mutations reduce offspring fitness across populations and time periods.

Older fathers' children have lower evolutionary fitness across four centuries and in four populations

Higher paternal age at offspring conception increases de novo genetic mutations. Based on evolutionary genetic theory we predicted older fathers' children, all else equal, would be less likely to survive and reproduce, i.e. have lower fitness. In sibling control studies, we find support for negative paternal age effects on offspring survival and reproductive success across four large populations with an aggregate N > 1.4 million. Three populations were pre-industrial (1670-1850) Western populations and showed negative paternal age effects on infant survival and offspring reproductive success. In twentieth-century Sweden, we found minuscule paternal age effects on survival, but found negative effects on reproductive success. Effects survived tests for key competing explanations, including maternal age and parental loss, but effects varied widely over different plausible model specifications and some competing explanations such as diminishing paternal investment and epigenetic mutations could not be tested. We can use our findings to aid in predicting the effect increasingly older parents in today's society will have on their children's survival and reproductive success. To the extent that we succeeded in isolating a mutation-driven effect of paternal age, our results can be understood to show that de novo mutations reduce offspring fitness across populations and time periods.

Parental age and childhood cancer risk: A Danish population-based registry study

BACKGROUND

Though the association between parental age at child's birth and the risk of childhood cancer has been previously investigated, the evidence to date is inconclusive and scarce for rarer cancer types.

METHODS

Cancer cases (N=5,856) were selected from all children born from 1968 to 2014 and diagnosed from 1968 to 2015 in Denmark at less than 16 years of age listed in the nationwide Danish Cancer Registry. Cases were individually matched to controls (1:100) on sex and year of birth with a total of 585,594 controls randomly sampled from all live births in Denmark from the Danish Central Population Registry. Parental age at child's birth was extracted from the Central Population Registry. Conditional logistic regression models were used to estimate odds ratios for the association between parental age at child's birth and childhood cancer risk. Parental age was modeled as both categorical (referent group, parents aged 25-29) and continuous per 5-year increase in age.

RESULTS

Offspring of older mothers were at an increased risk of acute lymphoblastic leukemia [OR=1.10, 95% CI: (1.02, 1.19) per 5-year increase in age]. Older maternal age (40+) increased the risk of non-Hodgkin lymphoma [OR=1.96, 95%CI: (1.12, 3.43)]. The risk of Wilms' tumor also appeared elevated with older paternal age [OR=1.11, 95% CI: (0.97, 1.28) per 5-year increment in age].

CONCLUSION

Older parental age was a risk factor for various childhood cancers in Danish children. Further investigation of the biological and social factors that may be contributing to these associations is warranted.

Environmental influences on ovarian dysgenesis - developmental windows sensitive to chemical exposures

A woman's reproductive health and ability to have children directly affect numerous aspects of her life, from personal well-being and socioeconomic standing, to morbidity and lifespan. In turn, reproductive health depends on the development of correctly functioning ovaries, a process that starts early during fetal life. Early disruption to ovarian programming can have long-lasting consequences, potentially manifesting as disease much later in adulthood. A growing body of evidence suggests that exposure to chemicals early in life, including endocrine-disrupting chemicals, can cause a range of disorders later in life, such as those described in the ovarian dysgenesis syndrome hypothesis. In this Review, we discuss four specific time windows during which the ovary is particularly sensitive to disruption by exogenous insults: gonadal sex determination, meiotic division, follicle assembly and the first wave of follicle recruitment. To date, most evidence points towards the germ cell lineage being the most vulnerable to chemical exposure, particularly meiotic division and follicle assembly. Environmental chemicals and pharmaceuticals, such as bisphenols or mild analgesics (including paracetamol), can also affect the somatic cell lineages. This Review summarizes our current knowledge pertaining to environmental chemicals and pharmaceuticals, and their potential contributions to the development of ovarian dysgenesis syndrome. We also highlight knowledge gaps that need addressing to safeguard female reproductive health.