In which preterm labor-patients is intravenous maintenance tocolysis effective?

Aim: We evaluated whether maintenance tocolysis (intravenous ritodrine hydrochloride and/or magnesium sulfate) was effective in cases of spontaneous preterm labor with intact membranes. Methods: One hundred and thirty preterm labor patients who reached 36 weeks of gestation by maintenance tocolysis were selected. Immediate delivery (ID) after ceasing maintenance tocolysis was defined as an ‘effective case’. The correlated factors between ID and no immediate delivery (NID) were statistically analyzed. Results: Thirty-six patients delivered < two days after ceasing maintenance tocolysis (27.7%) and were defined as effective cases. Multiple logistic regression analysis revealed that amniotic fluid interleukin-8 at admission (≥ 2.3 ng/mL; odds ratio [OR] 5.6, 95% confidence interval [CI] 2.1–17.6; P < 0.001), pre-pregnancy body mass index (≤ 21.4; OR 5.3, 95% CI 2.0–16.2; P < 0.001) and cerclage (OR 3.6, 95% CI 1.1–11.8; P = 0.028) were independent factors correlated with ID (< 2 days). Conclusion: Maintenance tocolysis may be effective in limited cases with mild intra-amniotic inflammation, in lean women and in cerclage cases. Maintenance tocolysis should be ceased in cases without these clinical factors when clinical symptoms disappear.