Asthma in Pregnancy: Attacks seem rare in labour

I was concerned to read that 10-20% of women experience an exacerbation of asthma during labour.1 In 40 years' practice as an obstetric physician, I never saw an attack of asthma in labour; and nor have other obstetricians and respiratory physicians that I have questioned at conferences. I wonder if any of the BMJ's readers have personal experience of managing asthma attacks in labour? This is important because women with asthma are very frightened of not being able to cope with asthma at delivery. Up to now I have reassured patients that this is very unlikely to be a problem.