Contractility of the myometrium; the rationale for pharmacological intervention in preterm labour.

Thank you for asking us to comment on the issues raised by Professors Åkerlund and Mars̆ál. We would like to thank them for their interest and comments. We agree that in some cases of preterm labour, tocolysis is contraindicated. In particular, if there is significant fetal distress it would be unwise to delay delivery. Since preterm labour is multifactorial, there are a range of precipitating causes which could result in fetal compromise to a greater or lesser extent. At one extreme tocolysis will be harmful (major abruption or fetal infection) and at the other it may be beneficial (uncomplicated preterm labour). We agree that a delay in delivery at very early gestational ages is likely to shift the balance in favour of an improved fetal outcome. Nevertheless, this remains to be demonstrated in a randomised trial. Since tocolysis could be harmful in certain situations, it is important to undertake a risk–benefit analysis for each individual patient.