Labour is one of the shortest yet most hazardous journeys humans take during their lifetime. Currently, our methods of identifying those fetuses at particular risk of compromise during labour are limited. Antepartum tests of placental reserve give little information about an individual fetus's ability to cope with passage through the birth canal and some might already have received a silent insult earlier in the pregnancy that places them at increased risk. In addition to the normal processes of labour, other, more unpredictable factors can act to place the fetus in acute danger.