Is human fertility declining?

A bivariate Poisson regression to analyse impact of outlier women on correlation between female schooling and fertility in Malawi

BACKGROUND

Women's levels of education and fertility are commonly associated. In Sub-Saharan Africa, the pace of decreasing fertility rates varies greatly, and this is linked to women's levels of education. However, this association may be influenced by unusual females who have uncommon measurements on both variables. Despite this, most studies that researched this association have only analysed the data descriptively, without taking into account the effect of potential outliers. This study aimed to examine the presence and impact of outlier women on the relationship between female education and fertility in Malawi, using regression methods.

METHODS

To analyse the correlation between women's schooling and fertility and evaluate the effect of outliers on this relationship, a bivariate Poisson model was applied to three recent demographic and health surveys in Malawi. The R software version 4.3.0 was used for model fitting, outlier computations, and correlation analysis. The STATA version 12.0 was used for data cleaning.

RESULTS

The findings revealed a correlation of -0.68 to -0.61 between schooling and fertility over 15 years in Malawi. A few outlier women were identified, most of whom had either attended 0 or at least 9 years of schooling and had born either 0 or at least 5 children. The majority of the outliers were non-users of modern contraceptive methods and worked as domestic workers or were unemployed. Removing the outliers from the analysis led to marked changes in the fixed effects sizes and slight shifts in correlation, but not in the direction and significance of the estimates. The woman's marital status, occupation, household wealth, age at first sex, and usage of modern contraceptives exhibited significant effects on education and fertility outcomes.

CONCLUSION

There is a high negative correlation between female schooling and fertility in Malawi. Some outlier women were identified, they had either attended zero or at least nine years of schooling and had either born zero or at least five children. Most of them were non-users of modern contraceptives and domestic workers. Their impact on regression estimates was substantial, but minimal on correlation. Their identification highlights the need for policymakers to reconsider implementation strategies for modern contraceptive methods to make them more effective.

Cassandra's prophecy: medic or mother? Exploring the relevance of age-related fertility decline to women in medicine

This commentary presents a response to 'Cassandra's prophecy' from the perspective of a final-year medical student, in an attempt to gauge the particular relevance of age-related fertility decline to female doctors. Women in the UK are increasingly trying to have children at an older age, with a resultant rise in the incidence of age-related fertility decline and obstetric problems. The literature suggests that the trend towards older motherhood is seen particularly among highly educated women, but that such women lack sufficient knowledge about how fertility and obstetric outcomes decline with age. Recent data indicate that female doctors have children significantly later than women in the general population, but are overall no more likely to remain childless. However, there is significant variation between different specialties; for instance, female surgeons have children significantly later and are more likely to be childless by age 35, as compared with both male surgeons and female doctors in other specialties. This commentary explores various explanations for and implications of these data, in the context of recent changes in NHS workforce gender demographics.

Is there a declining trend in ovarian function among infertility clinic patients?

BACKGROUND

There is a growing body of evidence that testicular function has decreased rapidly over the last 50 years. However, much less is known about corresponding trends in ovarian function. Herein, we examine the temporal changes in ovarian function in a large sample of infertile patients from the Czech Republic over a period of 14 years.

METHODS

In a retrospective study, we analysed a large body of data from women, 20-40 years of age, undergoing IVF/ICSI treatment between 1995 and 2008. We defined ovarian function using five variables: basal FSH level, estradiol (E2) level on the day of HCG administration, dose of gonadotrophins used for ovarian stimulation, number of retrieved oocytes and dose of gonadotrophins per oocyte. Controlling simultaneously for temporal changes in patient age and stimulation protocol, we applied generalized additive models to describe the temporal trends.

RESULTS

During the study period the mean age of the study population increased by 2.7 years. Whereas the basal FSH and gonadotrophin dose did not change over time, the E2 level and oocyte retrieval declined, and the dose of FSH per oocyte increased during the study period.

CONCLUSIONS

The results are indicative of a small, but detectable decrease in ovarian function over a period of 14 years, which is not causally related to the ageing population.

DEALING WITH CHINA'S FUTURE POPULATION DECLINE: A PROPOSAL FOR REPLACING LOW BIRTH RATES WITH SUSTAINABLE RATES

Decreasing population levels due to declining birth rates are becoming a potentially serious social problem in developed and rapidly developing countries. China urgently needed to reduce birth rates so that its population would decline to a sustainable level, and the family planning policy designed to achieve this goal has largely succeeded. However, continuing to pursue this policy is leading to serious, unanticipated problems such as a shift in the country's population distribution towards the elderly and increasing difficulty supporting that elderly population. Social and political changes that promoted low birth rates and the lack of effective policies to encourage higher birth rates suggest that mitigating the consequences of the predicted population decline will depend on a revised approach based on achieving sustainable birth rates.

Biodegradation of endocrine disrupters: case of 17beta-estradiol and bisphenol A

The biodegradation of 17 beta-estradiol (E2) and bisphenol A (BPA) was compared to that of a reference pollutant, sodium benzoate (SB), known for its high biodegradability. The biodegradation was measured using the Sturm test (ISO 9439 modified Sturm test). The susceptibility of the target pollutants to be degraded by microorganisms of activated sludge from a wastewater treatment plant (WWTP) was evaluated by the production of carbon dioxide (CO2). Sorption experiments onto inactivated sludge were carried out to assess the contribution of sorption in E2 and BPA removal during biological treatment in a WWTP. E2 was more adsorbed than BPA onto inactivated sludge, probably making it less accessible to assimilation by microorganisms. In fact, E2 was less biodegradable than BPA with 66% and 74% of theoretical CO2 formation (Th(co2)) in 28 days, respectively. However, E2 showed faster biodegradation than BPA due to the shorter adaptation time of the microorganisms to start the assimilation. Final concentrations were measured and revealed that, under Sturm test conditions, E2 was totally removed from the aqueous phase while some traces of BPA were detected. This result could be explained by the lower adsorbability of BPA observed in adsorption experiments onto inactivated sludge. To investigate competition in a bi-component solution, Sturm tests were carried out with BPA/SB and E2/SB. Moreover, the biodegradation curves obtained did not indicate a toxicity of the target compounds towards microorganisms, which rapidly degraded SB. In the case of BPA/SB, an inflection in the curve confirmed the adaptation time of 4-5 days for BPA to be degraded.

Analysis of endocrine disrupting compounds in wastewater and drinking water treatment plants at the nanogram per litre level

The determination of steroid hormones, alkylphenolic compounds and bisphenol A at the ng l(-1) level in environmental water samples (surface water and WasteWater Treatment Plant samples (WWTP)) is performed by a specific analytical procedure. Pre-concentration by solid-phase extraction conditions was optimized using C18 cartridges for steroid hormones and polymeric Oasis HLB cartridges for phenolic compounds. Identification and quantification were performed using a LCMS/MS system with electrospray ionization in the negative mode for both compound families. For steroid hormones, the need to have limits of detection lower than 0.5 ng l(-1) in WWTP samples led to the improvement of a purification step on silica cartridges. In the case of the phenolic compounds, no purification was required because of their lower estrogenicity. The limits of detection in WWTP effluents ranged between 0.02 ng l(-1)and 0.21 ng l(-1) for steroid hormones and 0.4 and 10.2 ng l(-1) for phenolic compounds. The method was then applied to determine concentrations of the target compounds at each step of a WWTP. The process efficiencies were evaluated. Finally, concentrations were measured in influents and effluents of a Drinking Water Treatment Plant showing the complete removal of estrogenicity.