Method to evaluate intravenous maintenance tocolysis for preterm labor

Despite the lack of evidence-based medicine, continuous intravenous maintenance tocolysis is the main treatment for preterm labor (PTL) in Japan because it is considered to prolong the gestational period. This treatment needs to be evaluated in more detail, and we herein propose one method to assess maintenance tocolysis using the timing of delivery by PTL patients.

PTL patients (n = 307) were divided into three groups according to delivery weeks of gestation. Group A (severe PTL) delivered at <34 weeks, group B (mild PTL) at 34-37 weeks and group C (cases suspected overtreatment) at ≥38 weeks. The percentages of patients in each group was calculated and clinical characteristics were compared between groups.

The percentages of patients (%) in groups A, B and C were 33.9, 43.6 and 22.5, respectively. Gestational weeks on admission, maternal white blood cell count and C-reactive protein, PTL index, fetal fibronectin levels in vaginal secretions, amniotic fluid interleukin-8 levels, staying at neonatal intensive care unit were significantly different between these three groups by analysis of variance. Furthermore, amniotic fluid interleukin-8 levels were significantly higher in group B (3.5 [0.1-46.5] ng/mL) than in group C (1.7 [0.1-16.1], P < 0.05).

PTL patients were classified according to the prognosis. The ratio of patients in each group represented the severity of PTL and the risk of overtreatment. When this ratio is investigated on a nationwide scale, the use of intravenous maintenance tocolysis or definition of PTL may need to be reconsidered.