Their job is to birth Newchildren for the community. They are not allowed to apply for a Family Unit nor have spouses after their training. They cannot take the pills (used to prevent Stirrings) while pregnant, likely due to the hormonal changes they induce. Out of all the professions, they require the least training, along with Laborers. After 3 years of being a birthmother, they become Laborers. Before they become Laborers, they have a very luxurious, yet boring, life as a Birthmother. They hold very low profiles in the community.
While giving birth, they wear masks to prevent them from seeing the Newchildren and to prevent them from seeing their partner during sexual intercourse. They have three different partners in total. Most Birthmothers give birth naturally, but in Claire's case, she had to have a Caesarean section.