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Gender Birth Ratios

Volume 563: debated on Tuesday 21 May 2013

Following a request from the Council of Europe Parliamentary Assembly, the Department of Health has undertaken an analysis to investigate whether the gender birth ratio in the United Kingdom varies by mothers’ country of birth beyond the range that might be expected to occur naturally. The analysis concludes that when broken down by the mothers’ country of birth, no group is statistically different from the range that we would expect to see naturally occurring. However, there are significant limitations in what these data can show. As there are small numbers of births for most groups, large differences in birth rates would be needed to identify ratios outside the normal range.

The UK gender ratio is 105.1 male to 100 female births and is well within the normal boundaries for populations.

Evidence suggests that a number of factors can influence the sex of a child. These include paternal and maternal age, coital rates, number of children and sex of previous children. However, ratios above 108 and below 103 are unlikely to occur naturally other than as a product of the random variability associated with small numbers of births.

Recorded birth ratios vary widely by mothers’ country of birth. Initial analysis identified a small number of countries for which there were indications that birth ratios may differ from the UK as a whole and potentially fall outside the range considered possible without intervention. However, departmental analysts emphasised that it is possible that this was the product of natural variation and that further analysis would be undertaken.

The further analysis was quality assured by the methodology team at the Office for National Statistics and identified 10 countries which over the period 2007 to 2011 had over 10,000 births and recorded gender ratios either lower than 103 (seven countries) or higher than 108 (three countries). However, the tests undertaken indicate a strong probability that this is occurring by chance. Only one country, Sri Lanka, was found to have a birth ratio significantly different from the figure of 105.1 for the UK as a whole. Mothers born in Sri Lanka have a birth ratio of 99.2 or 99 male children for every 100 female children. However, this is not statistically significantly lower than the 103 threshold and again is likely to be the result of random variation, particularly given the relatively small numbers involved.

The Department of Health will repeat this analysis on an annual basis following publication of birth data.

“Birth ratios in the United Kingdom: a report on gender ratios at birth in the UK” has been placed in the Library. Copies are available for hon. Members in the Vote Office and for noble Lords in the Printed Paper Office.

The documents can also be accessed at: