In a retrospective study, the outcome of pregnancy and labour in 87 consecutively delivered asthmatic patients with singleton pregnancies was compared to that in a group of normal controls matched for maternal age and parity. Asthmatic patients had a higher incidence of low-birth-weight (less than 2500 g) babies, which was mainly found in those not requiring bronchodilator therapy. Bronchodilator therapy in asthmatic mothers was not associated with an increased incidence of preterm or post-term deliveries, low birth weight or big (greater than 90th centile) babies, induction of labour, instrumental deliveries, postpartum haemorrhage, or perinatal complications, when compared with asthmatic mothers not requiring treatment. The higher Caesarean section rate in the asthmatic mothers is mainly found in the group with bronchodilator therapy, and may be related to a slightly but not significantly higher rate of induction in these mothers. An increased rate of instrumental deliveries was found in asthmatic mothers, which is probably related to the use of epidural analgesia. The results indicate that asthma, if well controlled, does not significantly affect the outcome of pregnancy and labour.