Direct evidence of fetal responses to noxious stimulations: a systematic review of physiological and behavioral reactions

Fetal pain is usually debated using data extrapolated from physiology and anatomy; whereas direct observation of fetal pain reactions is only marginally used. We present the first systematic review to carefully analyse this direct evidence. Our objective was to summarize the scientific literature based on the direct observation of fetal responses to noxious stimulation. We retrieved 17 clinical studies focused on the direct observation of fetal responses to noxious stimulation. This systematic review suggests that direct trials of fetal responses to acute pain/stress caused by tissue injury are scarce, but nonetheless informative for therapeutic interventions using fetal surgery or fetal invasive procedures. The current evidence indicates that responses to fetal pain develop from mid-gestation onward, but further high-quality research is needed to confirm these findings and guide clinical practice.