There are several studies showing that fetuses can feel pain at 20 weeks after conception. Several situations are potentially painful for fetuses, such as malformations and invasive procedures. Nociceptive pathways are known to be functional at 26 weeks. Even if it is not possible to evaluate the fetal experience of pain, it is essential to examine its immediate and long-term consequences. As early as the beginning of the second trimester, hemodynamic and hormonal responses are observed following fetal nociceptive stimulation, In experimental studies, long-term changes have been noted in the corticotrop axis, subsequent responses to pain, and behavior after perinatal nociceptive stimulation.

This review would give answer to this controversial question : Fetal Pain

A Systematic Multidisciplinary Review of the Evidence

Susan J. Lee, JD; Henry J. Peter Ralston, MD; Eleanor A. Drey, MD, EdM; John Colin Partridge, MD, MPH; Mark A. Rosen, MD JAMA. 2005;294(8):947-954. doi:10.1001/jama.294.8.947

Thus, should fetal surgery be performed with fetal anesthesia?

I have always thought that because pre-term infants have been shown, in multiple studies, to have less sensitivity to experimental pain at later ages, their reflexive, implicit memory pathways have not matured sufficiently to have the type of nociceptive experience that we would describe as pain. (I know that it is dangerous to make this assumption!) Also, the phenomenon of infantile amnesia (the inability of children to explicitly recall events prior to age 3) argues against any mental experience other than an implicit, reflexive pathway type. Of course, the implicit, explicit pathways generally refer to memory pathways and I suppose that the fetus could experience pain without any sort of memory of it, but this does not make sense to me.

Thanks Carlo, for the citation. I will check that out.

Oops! Just notice that the citation was provided by Philippe. Thanks Philippe!

Nonetheles, even in the case of absence of pain memory, events such as surgery, shots and intubation appear to be instantaneously harmful to the baby: he/she can even have no memory but in that instant he/she is upsed and disturbed severely...

Plese, read also our review: Bellieni CV, Buonocore G. Is fetal pain a real evidence? J Matern Fetal Neonatal Med. 2012 Aug;25(8):1203-8.

Carlo, Your documentation that fetuses experience pain and suffering is excellent and to me indicates that we should respect that fetuses do retain some level of implicit memory of the event. The question as to whether to use fetal anesthesia hinges on the risks of pain and the risk of fetal anesthesia or analgesia which you also seem to agree with given your conclusions to your study below.

Excellent question. Excellent investigations. Keep up the good work!

Use of fetal analgesia during prenatal surgery.

Bellieni CV, Tei M, Stazzoni G, Bertrando S, Cornacchione S, Buonocore G.

CONCLUSION:

Fetal direct analgesia is performed only in a minority of cases and no study gives details about fetal reactions to pain. More research is needed to assess or exclude its possible long-term drawbacks, as well as the actual consequences of pain during surgery.

One thing more: Eric Kandel, has stated in his new text, The Principles of Neuroscience Fifth Edition, that Classical Conditioning, synergistically amplifies long term sensitization. To the extent that fetal vision and hearing is obtunded, the effect of Classical Conditioning during fetal surgery due to the otherwise neutral stimuli detected by hearing or vision will be obtunded also. Thus, the Pavlovian "conditioned response" is unlikely to include sight or sound stimuli which would act, after birth, to turn the attention of child on a similar procedure and thereby raise pain perception further.

So, to some extent, this mimics the case of children who undergo general anesthesia for painful procedures. It is the only time you can get long-term sensitization without being accompanied by classical conditioning. Children undergoing general anesthesia do not have vision to record the neutral stimuli of the operating room. Therefore, neutral visual stimuli cannot be paired with surgical procedure pain to unconsciously produce the conditioned response of elevated heart rate, elevated respiration, activated adrenals etc. This is probably why the need for pre-emptive analgesia is so difficult to find. Classical conditioning is not there to amplify the effect of long term sensitization.

The last time I looked, (which has been several years) only one systematic review was finding a need for it. In pediatric dentistry we use the child's heart rate to indicate break-through pain during dental procedures performed under general anesthesia. We will give local anesthesia for any procedure that raises or is likely to raise, their heart rate. If the mother is given anesthesia and during fetal surgery and the fetal heart rate does not go up, then this, to me, indicates that direct fetal analgesia would be unnecessary.

But this is a "a posteriori ratione" way, i.e. this assesses pain after that pain has been provoked; while pain should always be prevented. I agree that fetal heart rate should be used in a future study to assess pain and then decide whether fetal analgesics are necessary in the future of surgery.

True that it is better to prevent pain than to treat it after its occurrence because once pain signaling transits the neural synapses, long term sensitization may result. Therefore, when I am performing a procedure that my experience has informed me is likely to raise heart rate during general anesthesia, I use direct "pre-emptive" analgesia. Otherwise, I use heart rate to inform me. Ultimately, the risk of the procedure to place the fetal analgesia directly must be weighed against the risk of sensitizing the fetus by not placing it. This is difficult because until we can map the nociceptive centers of the fetal brain, we are only guessing as to the character of implicit pain that is really occurring. The objective measure of Heart rate has proven to be a poor substitute for self report, which no fetus can give us (other than a behavioral report). No doubt some poor monkey fetus brain is on some future researcher's Functional Magnetic Resonance Imaging calendar! (Has that been done?)