It turns out that no one really knows what it feels like to be a fetus. Through different interpretations of accumulating evidence, various scientists have estimated that pain becomes possible anywhere from 18 to 29 weeks into gestation, maybe later...
... One of the first clues that fetuses might feel pain came in the early 1990s, when researchers in England stuck needles into second-trimester fetuses and observed the release of pain-related hormones and nerve-signaling molecules. Before that, doctors thought the fetal nervous system was too undeveloped to feel pain. Even newborns endured surgeries without anesthesia.
"If you or I had that experience," Derbyshire said, "we would wake up and complain loudly."
Some of Anand's earliest research showed that newborns were far more likely to survive operations when given anesthetics. That made him wonder what happens before birth.
Since then, he said, studies have shown that the fetal brain and body are coordinated enough to experience pain by between about 18 and 20 weeks. When a fetus of that age gets a blood transfusion, for example, changes in heart rate and blood pressure accompany shifts in circulation and spikes in stress hormones. A morphine-like drug calms all of those responses down.
"The die-hards will say these are all reflexes," Anand said. But new evidence, he argued, suggests that the very young brain is developed enough in the right places to take in those sensations and translate them into pain.
"It's excruciating," he said. "Not only is sensitivity to pain higher in the fetus, it doesn't know when the pain is going to end."