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In response to Cheetham,1 as stated, our study was able only to address the relative risk to the second twin given the nature of the data.2 We previously addressed both absolute risk and the effect of caesarean section using record linkage of the Scottish Morbidity Record and the Scottish Stillbirth and Infant Death Enquiry. This linkage provides both the numerator and denominator required for the comparisons proposed.
The absolute risk of perinatal death for second twins born at term was 1 in 270 for all causes, 1 in 350 for death due to intrapartum anoxia, and 1 in 500 for anoxic death due to a mechanical cause.3 Planned caesarean section is associated with a lower risk of perinatal death and, if causality is assumed, the number needed to treat is 264 caesarean deliveries to prevent each death.4 These numbers reflect higher absolute risks than calculated by Cheetham. This may reflect flaws in the assumptions of his calculations. It may also reflect the observation that, although the second twin was at increased risk of death at term in both populations, the relative risk was higher in Scotland. We cannot address whether this reflects a greater absolute risk to the second twin in Scotland or to the first twin in England, Northern Ireland, and Wales.
Competing interests: None declared.