The effects of probiotics administration during pregnancy on preeclampsia and associated maternal, fetal, and newborn outcomes: a systematic review and meta-analysis

OBJECTIVE: This study aimed to synthesize the available evidence on probiotic administration during pregnancy for the prevention of preeclampsia and its effects on related maternal, fetal, and newborn outcomes. DATA SOURCES: Six databases were systematically searched for eligible studies, namely Ovid MEDLINE, Embase, CINAHL, Cochrane, Global Index Medicus, and the Maternity and Infant Care Database, from inception to August 2, 2023. STUDY ELIGIBILITY CRITERIA: Randomized controlled trials that evaluated the effects of probiotic administration on women during any stage of pregnancy were eligible for inclusion. METHODS: The protocol was registered with the International Prospective Register of Systematic Reviews under identi fier CRD42023421613. Evaluating study eligibility, extracting data, assessing risk of bias (ROB -2 tool), and rating certainty (Grading of Recommendations, Assessment, Development and Evaluations) were conducted independently by 2 authors. The primary outcomes were incidence of preeclampsia, eclampsia, and maternal mortality. A meta -analysis was performed, and the results were reported as risk ratios with 95% con fidence intervals. RESULTS: A total of 29 trials (7735 pregnant women) met the eligibility criteria. There was heterogeneity across the trials in the population of enrolled women and the type of probiotic tested (20 different strains), although most used oral administration. Probiotics may make no difference to the risk of preeclampsia (risk ratio, 1.14; 95% confidence interval, 0.84 -1.53; 11 trials; 2401 women; low certainty evidence), preterm birth at <37 weeks ' gestation (risk ratio, 0.93; 95% confidence interval, 0.66 -1.30; 18 trials, 4016 women; low certainty evidence), or gestational age at delivery (mean difference, -0.03 weeks [10.2 days]; 95% confidence interval, -0.16 to 0.10 weeks [approximate to -1.1 to 0.7 days]; 13 trials, 2194 women; low certainty evidence). It is difficult to assess the effects of probiotics on other secondary outcomes because the evidence was of very low certainty, however, no bene fits or harms were observed. CONCLUSION: Limited evidence suggests that probiotic supplementation does not affect the risk for preeclampsia. Further high -quality trials are needed to de finitively assess the bene fits and possible harms of probiotic supplementation during pregnancy. There is also a lack of data from trials that included women who were undernourished or who experienced microbial dysbiosis and for whom probiotic supplementation might be useful.