Umbilical cord
Molly's umbilical cord
An umbilical cord functioned as a connection between pre-born mammals and their mothers that delivered blood and nutrients. The attachment ran from the infant's navel to the placenta located in the mother's uterus.
In 2366, Jean-Luc Picard described the android Lal's dependency on her "father" Data to Vice admiral Haftel by saying that the umbilical cord (in this case, metaphorical) was virtually uncut. (TNG: "The Offspring")
In 2368, Worf cut newborn Molly O'Brien's umbilical cord while delivering her when the USS Enterprise-D was experiencing the effects of a quantum filament. (TNG: "Disaster")