This subject was unclear until recently when a growing body of evidence suggests that a foetus does feel pain early in pregnancy.
According to research studies in the field of prenatal surgery, an unborn baby can feel pain in first trimester. By the 20th week of gestation, the baby not only feels pain, but has a higher pain sensitivity than adults.
In a study of foetal pain, it was found that a foetus has receptors of pain at 7 weeks gestation. These receptors develop around the mouth and then spread to the whole face, palms and hands by 11 weeks, the trunk and upper arms and legs by 15 weeks, and the rest of the body by 20 weeks. The part of the brain that responds to pain, the neocortex, also begins developing at 8 weeks, and is fully formed by 20 weeks. By then, the foetus will react to pain by moving away from the stimulus in the same way as adults do.
The nervous pathway responsible for the most primitive response to pain, the spinal reflex, is in place by 8 weeks of pregnancy. This is the earliest point at which the foetus experiences pain. By 8-10 weeks, many of the neural connections are formed. This indicates that the brain has “wired” itself in the first trimester.
Another study has found that under minimal anaesthesia, the foetus withdrew from the scalpel and visibly flinched when touched by the knife. By increasing the amount of anaesthesia, flinching or other signs of foetal pain disappeared.
With painful stimulation, the body will react with the production of beta endorphins, cortisol, and noradrenaline. This stress response can be elicited by needling foetal tissues at 20 weeks gestational age. The umbilical cord with no pain receptors will not respond this way when it is similarly treated.