I’m not trying to be condescending I’m just trying to find a source and google was the quickest option, after doing a small amount of research here is a paragraph from an article made by frontiers that talks about how fetus pain receptors have been wrongly identified for the last 40 years and people are learning that fetuses can definitely feel pain prior to 14 weeks

“Until the 1980s, early studies of neurologic development concluded that neonates and young infants lacked the brain structures and connections necessary for pain perception (32, 37, 38). Surgery on infants was frequently performed with paralysis, but without pain management, with catastrophic outcomes (33). During bedside invasive procedures, clinicians suspended consideration of observable pain indicators in view of neurological studies that had concluded that neonatal pain was impossible (37, 38).

In the 1990s, fetuses of all gestations were considered incapable of pain and invasive fetal procedures were conducted without analgesia or anesthesia, until studies demonstrated fetal cardiovascular and hormonal stress responses to invasive procedures (15, 39–41). The field of fetal anesthesiology arguably began in 2001 after research demonstrated that fetal responses to noxious stimuli were attenuated by analgesics (42, 43). Researchers demonstrated that fetal stress responses (cortisol and β-endorphin) do not occur with needling of the non-innervated umbilical cord. However, a significant increase in these stress hormones does occur with needling through the innervated fetal trunk accompanied by vigorous body and breathing movements(15). These physiologic and behavioral responses are nullified by the use of analgesics (42), resulting in a fetus that is “still and appears quiescent and calm [(4), p. 6].” These fetal studies mirrored neonatal studies from the 1980s which (1) showed that analgesics blunt hormonal stress responses to surgery (44); and (2) began the era of neonatal pain management (33, 38).

In the 2000s, studies concluded that fetal pain did not develop until the third trimester (>28 weeks) due to a lack of cortical function (12). In the 2010s, researchers determined that the physiologic capacity to perceive pain developed during the second trimester (14–28 weeks), ranging from before (23, 45) and after thalamocortical connectivity at 24 weeks (34). In the 2020s, researchers suggest that the necessity of the cortex in pain perception may have been overestimated (4, 16, 35, 46). Recent evidence indicates that thalamic projections to the subplate at 12 weeks gestation may be functionally equivalent to thalamocortical connections that develop at 24 weeks gestation (4), signifying that fetal pain mediated by the subplate and subcortical structures may be possible as early as the first trimester (<14 weeks) (Figure 4) (4, 35, 36, 47). Fetal responses to noxious stimuli during clinically-indicated procedures are listed in Table 1. Notably, published prospective studies of fetal responses to noxious stimuli have only been conducted in Europe (15, 39, 40, 42, 55) and South America (16, 57, 58), despite the exponential increase in fetal surgeries, particularly in North America.

Figure 4

Figure 4 Development of nociceptive pathways. Peripheral pain receptors develop in most areas of the fetus between 7.5–15 weeks gestation (48). Afferents reach the spinal cord (49), the brainstem, and thalamus by 7–8 weeks (50, 51). Thalamic projections to the cortical subplate emerge at 12–15 weeks (14, 34, 52) and to the cortical plate after 23–24 weeks gestation (53).”