No, Human fetus cannot feel pain at 20 weeks per three research studies mentioned.
Per conclusions of the 2005 JAMA study
Evidence Synthesis Pain perception requires conscious recognition or awareness of a noxious stimulus. Neither withdrawal reflexes nor hormonal stress responses to invasive procedures prove the existence of fetal pain, because they can be elicited by nonpainful stimuli and occur without conscious cortical processing. Fetal awareness of noxious stimuli requires functional thalamocortical connections. Thalamocortical fibers begin appearing between 23 to 30 weeks’ gestational age, while electroencephalography suggests the capacity for functional pain perception in preterm neonates probably does not exist before 29 or 30 weeks.
Conclusions Evidence regarding the capacity for fetal pain is limited but indicates that fetal perception of pain is unlikely before the third trimester. Little or no evidence addresses the effectiveness of direct fetal anesthetic or analgesic techniques. Similarly, limited or no data exist on the safety of such techniques for pregnant women in the context of abortion.
While the presence of thalamocortical fibers is necessary for pain perception, their mere presence is insufficient—this pathway must also be functional. It has been proposed that transient, functional thalamocortical circuits may form via subplate neurons around midgestation, but no human study has demonstrated this early functionality. Instead, constant SEPs appear at 29 weeks’ PCA, and EEG patterns denoting wakefulness appear around 30 weeks’ PCA. Both of these tests of cortical function suggest that conscious perception of pain does not begin before the third trimester. Cutaneous withdrawal reflexes and hormonal stress responses present earlier in development are not explicit or sufficient evidence of pain perception because they are not specific to noxious stimuli and are not cortically mediated.
Per conclusions of the 2006 study 'Can fetuses feel pain?'
The neuroanatomical system for pain can be considered complete by 26 weeks' gestation. A developed neuroanatomical system is necessary but not sufficient for pain experience. Pain experience requires development of the brain but also requires development of the mind to accommodate the subjectivity of pain. The absence of pain in the fetus does not resolve the morality of abortion but does argue against legal and clinical efforts to prevent such pain during an abortion.
Per conclusions of the 1999 study Fetal pain: implications for research and practice
The physical system for nociception is present and functional by 26 weeks and it seems likely that the fetus is capable of feeling pain from this stage.
The Royal College of Obstetricians and Gynaecologists' Fetal Awareness -- Review of Research and Recommendation for Practice (March 2010) says,
In reviewing the neuroanatomical and physiological evidence in the fetus, it was apparent that
connections from the periphery to the cortex are not intact before 24 weeks of gestation and,
as most neuroscientists believe that the cortex is necessary for pain perception, it can be
concluded that the fetus cannot experience pain in any sense prior to this gestation.
The American Congress of Obstetricians and Gynecologists issued a statement in 2012:
ACOG STATEMENT ON HR 3803
The American Congress of Obstetricians and Gynecologists (ACOG) opposes HR 3803, the District of
Columbia Pain-Capable Unborn Child Protection Act, and other legislative proposals that are not based
on sound science or that attempt to prescribe how physicians should care for their patients.
The medical profession produced a rigorous scientific review of the available evidence on fetal pain in Journal of the American Medical Association (JAMA) in 20051. The review concluded that fetal perception of pain is unlikely before the third trimester. No new studies since the publication of the JAMA paper have changed this dominant view of the medical profession.
1. Lee SJ, Ralston HJP, Drey EA, Partridge JC, Rosen MA. Fetal pain: A systematic multidisciplinary
review of the evidence. JAMA 2005; 294: 947-954.