Childbirth is painful, yet scientists are still somewhat in the dark about what actually causes the pain. A new doctoral thesis from the Swedish medical university Karolinska Institutet now shows where this pain comes from and opens the way to the development of improved methods of pain relief. In her thesis, obstetrician Berith Karlsson Tingåker has examined the source of pain during childbirth and how uterine sensitivity to pain changes during pregnancy.