Sex Ratio at Birth in Northern Ireland During the COVID-19 Pandemic: A Comparison With Published Data From the Republic of Ireland, England and Wales.

OBJECTIVES

The COVID-19 pandemic has been linked in several countries to fluctuations in the proportion of male live births/total live births, known as the sex ratio at birth (SRB). This study investigates how the pandemic influenced SRB patterns in Northern Ireland compared to published data from neighboring regions, including the Republic of Ireland with which it shares an open land border, and England and Wales, across the sea.

METHODS

Monthly live birth data for Northern Ireland from 2015 to 2021 were obtained from the Northern Ireland Statistics and Research Agency. A time series analysis predicted the SRB for 2020 using data from 2015 to 2019. Predicted and observed SRB values were compared for 2020.

RESULTS

In August 2020, 5 months after the pandemic declaration, the SRB fell significantly to 49.13%, the period's lowest, below the 95% prediction interval (50.09%-51.85%). In December 2020, 9 months after the declaration, the SRB rose to 54.48%, exceeding the prediction interval (49.75%-51.57%). This overall SRB pattern resembled that in England and Wales but differed from the Republic of Ireland.

CONCLUSION

The decline in SRB in August 2020, occurring 3-5 months after the pandemic declaration, suggests the pandemic disproportionately affected male fetuses in Northern Ireland. The rise in December, 9 months after the declaration, may relate to increased sexual activity in March 2020 following lockdown in a subset of the population. Northern Ireland's SRB pattern aligns more with England and Wales than the Republic of Ireland, indicating that socio-political ties in the United Kingdom may be more influential for pandemic response than geographical proximity.