More on the science of fetal pain

I'd like to add an interesting addendum to yesterday's post on Nebraska's Fetal Pain Law. A little more geared toward the science, this time. Dr. Anand asserts that the anatomical capacity for feeling pain begins to develop at about 7 weeks gestation, with the appearance of pain receptors around the mouth which then spread throughout the body, having completely populated the surface by week 20. Preceding the emergence of these pain receptors at the surface is the migration of the nerve fibers necessary to transmit impulses back to the spinal cord, where sensory information is integrated and directed to the appropriate brain structure for processing. In short, the presence of the surface pain receptor implies the presence of the appropriate neural circuitry to relay the sensory information that it collects back to the spinal cord. I'll spare you the fancy anatomical jargon of the brainstem nuclei and cortical connections that collect and relay sensory information collected by the spinal cord, but suffice it to say that the basic brainstem-level processing circuitry, relay circuitry, subcortical and cortical structures of the brain that are necessary for pain sensation and perception, including reflex responses to painful stimuli, all seem to be present and accounted for by the 20 week mark - if not sooner.

The major puzzle piece that is missing, however, is the modulatory circuitry responsible for inhibiting pain impulses, which doesn't even begin to develop until 32-34 weeks gestation. In practical terms, what this means is that the body's ability to deaden, numb, or mute pain signals is missing until late in the third trimester. Anyone who has endured any kind of acutely painful injury, say a broken bone for instance, has experienced this "numbing" effect. When our pain threshold is reached, our bodies begin to compensate for the shock to the nervous system by inhibiting the transmission of pain signals at various levels of the neural circuitry, effectively muting our perception of the painful stimulus, like turning down a dimmer switch. The absence of this inhibitory system in the fetus implies that not only can a 20-week-old fetus perceive pain, but that it most likely feels it far more intensely than a newborn or small child can. The system has developed the capacity to relay excitatory information (pain), but lacks the ability to transmit inhibitory information to restrain that excitation.

The science also demonstrates that the typical anesthetic doses given to mothers during abortion procedures are not even remotely sufficient to appropriately anesthetize the fetus. Typical nerve block methods (such as epidural anesthesia) confer no pain relief to the fetus whatsoever, because they only block maternal nerves below a certain spinal level. And general anesthetics, while they can cross the placenta and fetal blood-brain barrier to provide some level of relief, have been shown time and time again to require significantly higher doses to achieve the same effect in the fetus as in the adult. Levels of anesthetic high enough to realistically ensure that a sufficient amount successfully escapes breakdown by the maternal liver, crosses the placenta and anesthetizes the fetus would be toxic to the mother.

Further evidence for the ability of the fetus to feel pain is provided by hormonal studies carried out on fetuses that required intrauterine blood transfusion, accomplished by piercing the fetal abdominal cavity with a needle and placing it in the intrahepatic vein (in the liver). Stress hormone levels (cortisol, catecholamines and beta-endorphin) as well as heart rate rapidly increased in these subjects following insertion of the needle, but the magnitude of the response was greatly reduced following administration of the opiate pain-killer fentanyl. Furthermore, fetuses transfused through the umbilical cord (which is not innervated) showed no change in stress hormone levels at all, indicating that the response was not induced by the transfusion itself, but specifically by the perception of pain.

Most of this information was gleaned from one review article (http://www.nrlc.org/abortion/fetal_Pain/AnandPainReport.pdf), but like I said, search PubMed and you will find that Dr. Anand is not the only scientist that is doing this work and reaching these disturbing conclusions. It's time to accept the fact that a developing fetus is more than just a human-shaped lump of tissue - it's a feeling, perceiving, reacting, experiencing human child. A child who deserves a chance, and needs someone to step up and fight for his or her rights too.