December 2, 2021

expert reaction to study looking at pollutants and sex ratio at birth

A study published in PLOS Computational Biology looks at variations in human sex ratio at birth.

Dr Gareth Nye, Lecturer in Physiology (Pregnancy and postnatal medicine) at Chester Medical School, University of Chester, said:

“I think the press release does reflect the paper well. The number of births used in this study is small. There is an average of 3.8 million births per year in the US annually, which is more than the number of births used in this 8-year data set. This doesn’t necessarily mean it’s of lower quality but does indicate the conclusions may not be as certain. The thinking is that pollutants may influence the very early stage of fertilisation, leading to one sex direction over another. Without cellular research, these will always be associations. This is retrospective data meaning they are relying on databases and data taken from the past. There is always some risk in using past data to make conclusions for the modern day. The authors themselves admit that their findings are contradictory, potentially due to the small number of births used in this study. They are only making associations and pollutants are one of many linked with proposed changes in sex at birth. There is no doubt that pollutants play roles in health and disease and that this form of computational research has a role in helping us understand why. This study however does not convince me that pollution can change the sex at birth ratio.”

‘Observable variations in human sex ratio at birth’ by Yanan Long et al. was published in PLOS Computational Biology at 7pm UK Time on Thursday 2 December 2021.

DOI: https://doi.org/10.1371/journal.pcbi.1009586

Declared interests

Dr Gareth Nye: no conflicts.