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. 2023 Feb 17:11:e14618.
doi: 10.7717/peerj.14618. eCollection 2023.

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

Gwinyai Masukume  1 , Margaret Ryan  2 , Rumbidzai Masukume  3 , Dorota Zammit  4 , Victor Grech  5 , Witness Mapanga  6   7 , Yosuke Inoue  8
Affiliations

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

Gwinyai Masukume et al. PeerJ. .

Abstract

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.

Keywords: COVID-19; England; Lockdown; Population stressor; Sex ratio at birth; Sexual intercourse; Wales.

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Conflict of interest statement

The authors declare there are no competing interests. Witness Mapanga is employed by Wits Health Consortium (PTY) Ltd.

Figures

Figure 1
Figure 1. Total live births over 9 years, from January 2012 to December 2020.
Figure 2
Figure 2. Monthly proportion of male live births over 9 years, from January 2012 to December 2020.
Figure 3
Figure 3. Observed and predicted sex ratio at birth (SRB) in 2020.
See this image and copyright information in PMC

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