This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To determine whether maternal probiotic administration to pregnant women at risk of preterm birth and/or probiotic administration to mothers after preterm birth compared to administration of placebo, no intervention or postnatal administration to preterm infants reduces the risk of morbidity and mortality in preterm infants.

Comparisons:

(1): Probiotics administered to pregnant women at risk of preterm birth (< 37 weeks' gestation) vs. placebo or no intervention.

(a): In pregnant women at risk for preterm birth (< 37 weeks' gestation), maternal probiotics only prior to birth versus maternal placebo or no intervention prior to birth;

(b): In pregnant women at risk for preterm birth (< 37 weeks' gestation), maternal probiotics both prior to and after birth versus maternal placebo or no intervention prior to and after birth.

(2): Probiotics administered exclusively after birth in mothers of preterm infants < 37 weeks' gestation versus maternal placebo or no intervention.

(3): Probiotics administered exclusively after birth in mothers of preterm infants < 37 weeks' gestation versus neonatal probiotic administration.