Context Proposed federal legislation would require physicians to inform women
seeking abortions at 20 or more weeks after fertilization that the fetus feels
pain and to offer anesthesia administered directly to the fetus. This article
examines whether a fetus feels pain and if so, whether safe and effective
techniques exist for providing direct fetal anesthesia or analgesia in the
context of therapeutic procedures or abortion.
Evidence Acquisition Systematic search of PubMed for English-language articles focusing on
human studies related to fetal pain, anesthesia, and analgesia. Included articles
studied fetuses of less than 30 weeks’ gestational age or specifically
addressed fetal pain perception or nociception. Articles were reviewed for
additional references. The search was performed without date limitations and
was current as of June 6, 2005.
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.
For fetal surgery, women may receive general anesthesia and/or analgesics
intended for placental transfer, and parenteral opioids may be administered
to the fetus under direct or sonographic visualization. In these circumstances,
administration of anesthesia and analgesia serves purposes unrelated to reduction
of fetal pain, including inhibition of fetal movement, prevention of fetal
hormonal stress responses, and induction of uterine atony.
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. Anesthetic techniques currently
used during fetal surgery are not directly applicable to abortion procedures.