Photobiomodulation–Nitric Oxide Signaling in Preeclampsia: A Systematic Scoping Review of Mechanistic and Clinical Evidence

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BSTRACT

Preeclampsia remains a cause of maternal and perinatal morbidity, with endothelial dysfunction, reduced nitric oxide (NO) bioavailability, oxidative stress, placental malperfusion, and angiogenic imbalance central to its pathophysiology. Photobiomodulation (PBM) can influence NO-related vascular signaling, but its relevance to preeclampsia and laser-based acupoint stimulation remain uncertain. We conducted a systematic scoping review mapping evidence linking PBM, NO/endothelial NO synthase signaling, vascular function, and preeclampsia. PubMed/MEDLINE, PubMed Central, Embase, Scopus, Web of Science, the Cochrane Library, and additional registers were searched from inception through March 31, 2026; study selection followed PRISMA guidance. Thirty-five evidence sources were included, spanning preeclampsia-specific clinical and observational studies, nonpregnant human studies, animal and experimental investigations, and reviews. PBM-related modulation of NO signaling, endothelial function, redox balance, microcirculation, and angiogenic pathways was biologically plausible; however, evidence directness varied considerably. Clinical evidence in women with preeclampsia was sparse and largely involved acupuncture or acupressure rather than PBM efficacy, while much of the PBM–NO evidence arose from non-pregnant or preclinical settings. Maternal–fetal benefit, improved placental perfusion, and pregnancy safety therefore remain unproven, and heterogeneous treatment parameters further limit translation. This review extends the contributors’ preliminary evidence-mapping work undertaken to assemble and organize data in this emerging field; it should be regarded as a foundation for hypothesis development rather than evidence for clinical implementation, particularly before any recommendation for routine obstetric practice can reasonably be considered. Pregnancy-specific studies should first establish dosimetry and maternal–fetal safety, followed by biomarker-informed prospective trials testing whether mechanistic effects translate into meaningful clinical outcomes.