The sex ratio at birth in South Africa may be a sentinel health indicator

et al. 2022

PeerJ

Self Cite

Background The sex ratio at birth (defined as male/(male+female) live births) is anticipated to approximate 0.510 with a slight male excess. This ratio has been observed to decrease transiently around 3–5 months following sudden unexpected stressful events. We hypothesised that stress engendered by the onset of the COVID-19 pandemic may have caused such a decrease in South Africa 3–5 months after March 2020 since in this month, South Africa reported its first COVID-19 case, death and nationwide lockdown restrictions were instituted. Methods We used publicly available, recorded monthly live birth data from Statistics South Africa. The most recent month for which data was available publicly was December 2020. We analysed live births for a 100-month period from September 2012 to December 2020, taking seasonality into account. Chi-squared tests were applied. Results Over this 100-month period, there were 8,151,364 live births. The lowest recorded monthly sex ratio at birth of 0.499 was in June 2020, 3 months after March 2020. This June was the only month during this period where the sex ratio inverted i.e., fewer male live births occurred. The predicted June 2020 ratio was 0.504. The observed June 2020 decrease was statistically significant p = 0.045. Conclusions The sex ratio at birth decreased and inverted in South Africa in June 2020, for the first time, during the most recent 100-month period. This decline occurred 3 months after the March 2020 onset of COVID-19 in South Africa. As June 2020 is within the critical window when population stressors are known to impact the sex ratio at birth, these findings suggest that the onset of the COVID-19 pandemic engendered population stress with notable effects on pregnancy and public health in South Africa. These findings have implications for future pandemic preparedness and social policy.

Section: Introductionmentioning

confidence: 99%

COVID-19 onset reduced the sex ratio at birth in South Africa

Masukume¹,

Ryan

et al. 2022

PeerJ

Self Cite

“…The secondary sex ratio, commonly known as the sex ratio at birth (SRB), is calculated as male divided by total live births ( Grech, 2014 ). The SRB may serve as a sentinel health indicator, revealing unfavourable conditions through a decline and better conditions through an increase ( Davis, Gottlieb & Stampnitzky, 1998 ; Grech & Masukume, 2016 ).…”

Section: Introductionmentioning

confidence: 99%

COVID-19 induced birth sex ratio changes in England and Wales

Ryan

et al. 2023

PeerJ

Self Cite

Background The sex ratio at birth (male live births divided by total live births) may be a sentinel health indicator. Stressful events reduce this ratio 3–5 months later by increasing male fetal loss. This ratio can also change 9 months after major population events that are linked to an increase or decrease in the frequency of sexual intercourse at the population level, with the ratio either rising or falling respectively after the event. We postulated that the COVID-19 pandemic may have affected the ratio in England and Wales. Methods Publicly available, monthly live birth data for England and Wales was obtained from the Office for National Statistics up to December 2020. Using time series analysis, the sex ratio at birth for 2020 (global COVID-19 onset) was predicted using data from 2012–2019. Observed and predicted values were compared. Results From 2012–2020 there were 3,133,915 male and 2,974,115 female live births (ratio 0.5131). Three months after COVID-19 was declared pandemic (March 2020), there was a significant fall in the sex ratio at birth to 0.5100 in June 2020 which was below the 95% prediction interval of 0.5102–0.5179. Nine months after the pandemic declaration, (December 2020), there was a significant rise to 0.5171 (95% prediction interval 0.5085–0.5162). However, December 2020 had the lowest number of live births of any month from 2012–2020. Conclusions Given that June 2020 falls within the crucial window when population stressors are known to affect the sex ratio at birth, these findings imply that the start of the COVID-19 pandemic caused population stress with notable effects on those who were already pregnant by causing a disproportionate loss of male fetuses. The finding of a higher sex ratio at birth in December 2020, i.e., 9 months after COVID-19 was declared a pandemic, could have resulted from the lockdown restrictions that initially spurred more sexual activity in a subset of the population in March 2020.

“…Notwithstanding the controversies, the 2D:4D digit ratios and the hormonal hypothesis are still popular among biologists globally. However, the relationship between the 2D:4D ratio and offspring sex at birth have seen little or no testing in the Ghanaian population and previous studies on offspring sex in Sub‐Saharan Africa are few and did not involve maternal (parental) 2D:4D ratios (Grech & Masukume, 2016; Masukume & Grech, 2015). The 2D:4D ratio and the sex ratio at birth in humans show population variabilities given to genetic and environmental factors (Boklage, 2005; Terrell et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

The association between the 2D:4D ratio and offspring sex at birth: A cross‐sectional study in Ghana

Banyeh

Amidu

2022

American J Hum Biol

Objectives The 2D:4D ratio is the putative marker of prenatal androgen exposure. Low maternal 2D:4D ratio has been associated with high or male‐biased secondary sex ratio. Hitherto, there has not been any study in Ghana regarding the maternal 2D:4D ratio and sex ratio at birth. This study sought to investigate this observation in a Ghanaian population. Method The study was cross‐sectional from December 2020 to April 2021 involving 272 first‐time mothers. The mean ± SD age of the mothers was 23.9 ± 3.67 years. The right (2D:4DR), the left (2D:4DL), the mean (M2D:4D) digit ratios and the right–left difference (Dr‐l) of the mothers were measured using computer‐assisted analysis. The mothers were stratified by their digit ratios, and the cohort sex ratio (CSR) for each stratum was then calculated as the proportion of sons. Results The mean ± SD of the 2D:4DR of mothers‐with‐daughters and mothers‐with‐sons were 0.941 ± 0.032 and 0.933 ± 0.037, respectively. The mean ± SD of the 2D:4DL of mothers‐with‐daughters was 0.934 ± 0.034, while that of mothers‐with‐sons was 0.931 ± 0.039. The offspring sex at birth and the CSR was not associated with either the mother's right, left, mean 2D:4D ratio or their difference (Dr‐l). However, mothers‐with‐daughters showed rightward asymmetry in their 2D:4D ratios as the Dr‐l significantly and positively deviated from zero (p < .010). Conclusion The maternal 2D:4D ratio may not be associated with their offspring sex at birth among first‐time mothers. This study adds to the limited data on studies regarding offspring sex at birth and the 2D:4D ratio in Ghana and Sub‐Saharan Africa.