Probiotic supplementation during pregnancy or infancy for the prevention of asthma and wheeze: systematic review and meta-analysis

Systematic review and meta-analysis of 20 randomized trials in pregnant women and infants, comparing probiotic supplementation with placebo or no probiotic. Many participants were at high risk for asthma because of family history or allergic disease; studies were conducted mainly in Europe, with additional trials in Australia, New Zealand, and Taiwan.

Probiotic supplementation was tested during pregnancy, infancy, or both, with maternal dosing typically starting in the third trimester and some regimens continuing after delivery in mothers and infants. Trials used Lactobacillus and Bifidobacterium strains, sometimes in combination, at doses ranging from about 1×10^8 to 2.4×10^10 CFU per day versus placebo or no probiotic.

Perinatal probiotic supplementation did not reduce doctor-diagnosed asthma or childhood wheeze, and the current trial evidence does not support probiotics for primary prevention of these outcomes. Across nine trials (3257 children), asthma risk was RR 0.99 (95% CI 0.81 to 1.21; I2=0%), and wheeze across nine trials (1949 children) was RR 0.97 (0.87 to 1.09; I2=0%). Lower respiratory tract infections were numerically higher with probiotics in six trials (1364 children; RR 1.26, 0.99 to 1.61; I2=0%). Withdrawal due to perceived side effects was uncommon and not clearly different from control (Peto OR 1.45, 0.66 to 3.17; eight trials, 2732 children).

Several outcomes were based on a limited number of trials and children, and follow-up may have been insufficient to fully capture later asthma. Probiotic strains, combinations, timing, and duration were heterogeneous, adverse events were inconsistently reported, and some trials imposed feeding restrictions, which limits generalizability.