Sorting pain out of salience: assessment of pain facial expressions in the human fetus

Abstract

Introduction:The question of whether the human fetus experiences pain has received substantial attention in recent times. With the advent of high-definition 4-dimensional ultrasound (4D-US), it is possible to record fetal body and facial expressions. Objective: To determine whether human fetuses demonstrate discriminative acute behavioral responses to nociceptive input. Methods: This cross-sectional study included 5 fetuses with diaphragmatic hernia with indication of intrauterine surgery (fetoscopic endoluminal tracheal occlusion) and 8 healthy fetuses, who were scanned with 4D-US in 1 of 3 conditions: (1) acute pain group: Fetuses undergoing intrauterine surgery were assessed in the preoperative period during the anesthetic injection into the thigh; (2) control group at rest: Facial expressions at rest were recorded during scheduled ultrasound examinations; and (3) control group acoustic startle: Fetal facial expressions were recorded during acoustic stimulus (500-4000 Hz; 60-115 dB). Results: Raters blinded to the fetuses' groups scored 65 pictures of fetal facial expressions based on the presence of 12 items (facial movements). Analyses of redundancy and usefulness excluded 5 items for being of low discrimination capacity (P.0.2). The final version of the pain assessment tool consisted of a total of 7 items: brow lowering/eyes squeezed shut/deepening of the nasolabial furrow/open lips/horizontal mouth stretch/vertical mouth stretch/neck deflection. Odd ratios for a facial expression to be detected in acute pain compared with control conditions ranged from 11 (neck deflection) to 1,400 (horizontal mouth stretch). Using the seven-item final tool, we showed that 5 is the cutoff value discriminating pain from nonpainful startle and rest. Conclusions: This study inaugurates the possibility to study pain responses during the intrauterine life, which may have implications for the postoperative management of pain after intrauterine surgical interventions

Facial expressions of acute pain in 23‐week fetus

“…Issues such as the use of anesthesia during medical termination of pregnancy, efficacy of anesthesia during invasive intrauterine procedures and presence of postprocedural fetal pain have major clinical implications. Recently, a tool for evaluating facial expressions related to acute pain was described in an experimental study and was used to assess pain in late third‐trimester human fetuses 2 . In order to investigate the presence of fetal pain during the second trimester, we evaluated fetal pain score in a 23‐week fetus undergoing cardiac surgery.…”

Foetal pain and anaesthesia during prenatal surgery

“…Fetal blood pressure monitoring is not yet feasible [139] Slowing of the fetal heart can be a sign of fetal hypoxaemia and acidosis, but can also be related to a decrease in temperature, maternal respiratory acidosis, or to the administration of drugs [140]. Some authors have tried to create a fetal pain assessment tool, to be used during prenatal surgery [141]. The current fetal monitoring during prenatal surgery is based on echocardiographic monitoring of fetal heart rate and contractility.…”

Fetal Pain in the First Trimester

“…As noted by researchers in 2019, "It is now recognised that the developing motor and sensory systems are able to function long before they have completed their neural maturation" (Borsani et al 2019, 225). This has raised growing concern that the necessity of the cortex for pain perception may have been overstated, and that fetal pain perception is possible even with an immature cortex (Bellieni 2020;Bernardes et al 2021a;Derbyshire and Bockmann 2020;Merker 2007).…”

“…These indices reflect the earlier development of the upper facial muscles compared Thill to the lower facial muscles. Fetal pain assessments have also been conducted using the NFCS during painful intramuscular injections prior to fetal surgery (Bernardes et al 2021a(Bernardes et al , 2021b(Bernardes et al , 2018. Facial expressions (horizontal mouth stretch, open lips, vertical mouth stretch, and brow lowering) were elevated in those fetuses receiving injections compared to controls.…”

“…Figure 3 shows fetal facial expressions in response to anesthetic injection into the fetal thigh during third trimester fetal surgery (Bernardes et al 2021b, 5). The 2021 Society of Maternal Fetal Medicine report, however, does not view such facial expressions in the late second and third trimesters as evidence of fetal pain, stating, “because the facial nucleus and circuitry required for facial expressions arise from the brainstem and not the cortex, these indirect measures do not reflect any experience of pain or suffering.” Such assertions, which conflict with accepted neonatal pain assessment tools at the same and earlier gestational ages, raise concerns about overreliance on neuroanatomical hypotheses, as was done in the era of untreated neonatal pain, rather than correlation with clinical behavior, context, and other markers of pain perception.

Figure 3.(A) Initial items from neonatal facial coding system and 2 supplementary items.

…”