The government-commissioned study is a setback for anti-abortion activists, who want the country's current 24-week time limit for terminations reduced.
The study says that nerve connections in the brain are not sufficiently formed to allow pain perception before 24 weeks.
The study by the Royal College of Obstetricians and Gynecologists, published Friday, was recommended by lawmakers who are considering lowering the abortion limit.
The doctors say there is increasing evidence that even after 24 weeks the fetus is in a state of "continuous sleep-like unconsciousness or sedation."
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