Background: Preterm prelabour rupture of the membranes (PPROM) complicates approximately 2% of pregnancies and can be either spontaneous or iatrogenic in nature. Complications of PPROM include prematurity, chorioamnionitis, neonatal sepsis, limb position defects, respiratory distress syndrome, pulmonary hypoplasia chronic lung disease, periventricular leukomalacia and intraventricular haemorrhage. A number of different sealing techniques have been employed which aim to restore a physical barrier against infection and encourage the re-accumulation of amniotic fluid. Routine use of sealants is currently not recommended due to a lack of sufficient evidence to support the safety and effectiveness of such interventions. Objectives: To assess the effects of sealing techniques following PPROM against each other, or versus standard care (including no sealant), on maternal and neonatal outcomes. Search methods: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 May 2016) and reference lists of retrieved studies. Selection criteria: Randomised and quasi-randomised controlled trials comparing different techniques for sealing preterm prelabour ruptured membranes. Cluster-randomised trials and trials using a cross-over design were not eligible for inclusion in this review. We planned to include abstracts when sufficient information was provided. Data collection and analysis: Two review authors independently assessed trials for inclusion and assessed trial quality. Two review authors independently extracted data. Data were checked for accuracy. Main results: We included two studies (involving 141 women - with data from 124 women). We considered both studies as being at high risk of bias. Meta-analysis was not possible because the included studies examined different interventions (both in comparison with standard care) and reported on few, but different, outcomes. One study compared cervical adapter (mechanical sealing), and the other study examined an immunological membrane sealant. Neither of the included studies reported on this review's primary outcome of interest - perinatal mortality. Similarly, data were not reported for the majority of this review's secondary infant and maternal outcomes. Cervical adapter (mechanical sealing) versus standard care (one study, data from 35 participants) No data were reported for this review's primary outcome - perinatal mortality. Data were reported for few of this review's infant or maternal secondary outcomes. There was no clear difference between the mechanical sealing group and the standard care control in relation to the incidence of neonatal sepsis (risk ratio (RR) 1.19, 95% confidence interval (CI) 0.28 to 5.09 (very low-quality evidence)) or chorioamnionitis (RR 1.19, 95% CI 0.28 to 5.09 (very low-quality evidence)). Oral immunological membrane sealant versus standard care (one study, data from 94 participants) No data were available for perinatal mortality (this review's primary outcome) or for the majority of this review's infant and maternal secondary outcomes. Compared to standard care, the immunological membrane sealant was associated with a reduction in preterm birth less than 37 weeks (RR 0.48, 95% CI 0.34 to 0.68 (very low-quality evidence)) and a reduction in neonatal death (RR 0.38, 95% CI 0.19 to 0.75 (very low-quality evidence)). However, there was no clear difference between groups in terms of neonatal sepsis (RR 0.64, 95% CI 0.28 to 1.46 (very low-quality evidence)) or respiratory distress syndrome (RR 0.64, 95% CI 0.28 to 1.46 (very low-quality evidence)). Authors' conclusions: There is insufficient evidence to evaluate sealing procedures for PPROM. There were no data relating to this review's primary outcome (perinatal mortality) and the majority of our infant and maternal secondary outcomes were not reported in the two included studies. There was limited evidence to suggest that an immunological membrane sealant was associated with a reduction in preterm birth at less than 37 weeks and neonatal death, but these results should be interpreted with caution as this is based on one small study, with a high risk of bias, and the intervention has not been tested in other studies. Although midtrimester PPROM is not a rare occurrence, there are only a small amount of published data addressing the benefits and risks of sealing procedures. Most of these studies are retrospective and cohort based and could therefore not be included in our data-analysis. This review highlights the paucity of prospective randomised trials in this area. Current evidence provides limited information both on effectiveness and safety for the interventions described. Given the paucity of high-quality data, we recommend that future research efforts focus on the conduct of randomised trials assessing the effect of promising interventions that have been only evaluated to date in cohort studies (e.g. amniopatch). Future trials should address outcomes including perinatal mortality, preterm birth, neonatal death, respiratory distress syndrome, neonatal sepsis and developmental delay. They should also evaluate maternal outcomes including sepsis, mode of delivery, length of hospital stay and emotional well-being.