Is there a role for maintenance therapy?

Professor James Grant Thornton
Department of Obstetrics and Gynaecology
University of Nottingham, City Hospital, Nottingham, UK

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Biography
James Grant Thornton is the Professor of Obstetrics and Gynaecology at the University of Nottingham, Nottingham, UK and is based at the City Hospital. He qualified in Leeds in 1977 and was Reader/Honorary Consultant in Leeds from 1989 until 2002. Previously, from 1979 until 1983, Professor Thornton was a General Medical Officer at Chogoria Mission Hospital in Kenya. Since 2003, he has been the Editor-in-Chief of the British Journal of Obstetrics and Gynaecology. His research interests are in clinical trials. His clinical interests are in maternal-fetal medicine, general obstetrics, general gynaecology and screening.

Abstract
Women who are undelivered after 48 hours of tocolysis remain at an increased risk of preterm labour. However, it is not clear whether prolonged tocolytic treatment is effective. Tocolytics have previously been considered unsuitable for maintenance treatment, as the risks have outweighed the benefits. However new oxytocin antagonists have an improved safety profile and may be more appropriate for maintenance therapy. The purpose of this presentation is to review the current evidence for the effectiveness of maintenance tocolysis using the results of published systematic reviews.

Five systematic reviews and two trials, published too recently for inclusion, were identified. Maintenance tocolysis with beta-agonists and magnesium sulphate was found to be ineffective in prolonging gestation or reducing any adverse fetal outcomes. One trial of maintenance tocolysis with nifedipine was underpowered to rule out an effect on prolonging gestation.¹ A recent systematic review including only this trial concluded that the role of maintenance therapy with calcium channel blockers for preventing preterm birth was not clear.² One trial of the oxytocin receptor blocker, atosiban, showed that this drug used as maintenance tocolysis does prolong gestation, but the trial was too small to demonstrate any reduction in substantive fetal outcomes.³

In summary, there is insufficient evidence to justify the routine use of maintenance tocolysis in preterm labour. However, it remains plausible that prolongation of gestation might be beneficial in selected cases of very preterm labour where fetal compromise and infection have been ruled out. Atosiban is the only tocolytic agent that has been shown to prolong gestation when used for maintenance therapy.³ 

References

1. Carr DB, Clark AL, Kernek K, Spinnato JA. Maintenance oral nifedipine for preterm labor: a randomised clinical trial. Am J Obstet Gynecol 1999;181:822–7.
2. Gaunekar N, Crowther C. Maintenance therapy with calcium channel blockers for preventing preterm birth after threatened preterm labour. Cochrane Database Syst Rev 2004;3:CD004071.
3. Valenzuela G, Sanchez-Ramos L, Romero R, et al. Maintenance treatment of preterm labor with the oxytocin antagonist atosiban. Am J Obstet Gynecol 2000;182:1184–90.