Artificial light at night during pregnancy: A systematic review of chronodisruption, placental bioenergetics, and neonatal outcomes in the era of urbanization and digital exposure

Abstract Artificial light at night (ALAN) has become an increasingly prevalent environmental exposure due to urban expansion, widespread LED lighting, and digital screen usage. During pregnancy, ALAN may suppress maternal melatonin secretion and disrupt circadian signaling, thereby impairing placental function and fetal development. Despite biologically plausible pathways linking ALAN to adverse perinatal outcomes, its relevance remains largely overlooked in clinical obstetrics. This systematic review synthesizes current evidence on ALAN exposure during pregnancy and its consequences for maternal circadian physiology, placental molecular pathways, and neonatal health. A total of 41 studies – comprising 18 human observational studies, 12 controlled animal experiments, and 11 mechanistic investigations – were identified through comprehensive database searches and screened using PRISMA 2020 methodology. ALAN exposure modalities included outdoor ambient light, nighttime digital screen use, and hospital lighting environments. Across models, ALAN was consistently associated with suppression of melatonin, dysregulation of circadian genes (BMAL1, PER1), increased oxidative stress, and impaired mitochondrial function in placental tissues. Clinically, higher ALAN exposure (≥3 h per night) was consistently associated with statistically significant increases in the risk of preterm birth, fetal growth restriction, and gestational diabetes, as well as alterations in neonatal cortisol rhythms and sleep–wake behavior. The risk was amplified with short-wavelength (blue) light exposure, suggesting a dose–response relationship. The findings position ALAN as a novel and modifiable environmental factor with direct relevance to perinatal health. Interventions focused on light hygiene, circadian-aligned hospital lighting, and maternal education represent practical, low-cost strategies to mitigate these risks. As digital exposure and artificial illumination become ubiquitous, promoting circadian-aligned light–dark patterns during pregnancy emerges as a critical frontier in maternal–fetal medicine.