Incidence data would be helpful
The suggestion in the article by Charles and colleagues that folate supplementation in pregnancy could increase the risk of later breast cancer is based on a total of 31 deaths. To increase the number of events the authors could have used incidence rather than mortality figures. As these data should be easily obtainable from Scottish Morbidity Records it would be helpful if the authors could report these to allow a better assessment of whether this hypothesis deserves further testing.
Competing interests: None declared
Competing interests: No competing interests