Preterm prelabour rupture of membranes (PPROM) is a common preterm birth antecedent. Preterm infants experience increased adverse newborn outcome risks. Infection is a risk factor for early birth in PPROM. Current management is antibiotic therapy, antenatal corticosteroids and to plan delivery at 37 weeks gestation. The microbiota and probiotics are potentially protective and may improve outcomes.

The primary aim is to evaluate whether oral probiotic therapy (Lactobacillus fermentum CECT5716) administered during PPROM between 24 and 34 weeks gestation prolongs pregnancy duration. The secondary aim is to evaluate maternal and neonatal outcomes.

Materials and Methods
This is a pragmatic, multicentre, double‐blind, placebo‐controlled randomised controlled trial in Australia. The population will be women with a singleton pregnancy and PPROM less than 34 weeks gestation. The intervention will be an oral probiotic therapy compared with a placebo control. The primary outcome will be the proportion of women still pregnant at seven days following PPROM. One‐to‐one randomisation will occur within 24 h of PPROM. The trial is powered (80%, alpha = 0.05) to detect an absolute percentage increase in the primary outcome of 30%, (from expected rate of 20% up to 50%).

This trial will provide evidence for the effectiveness of the probiotic in prolonging pregnancy duration. Findings will inform the feasibility of a larger trial to examine the effect of oral probiotics on clinically important maternal and neonatal outcomes in PPROM.