The mating system of baiji is unknown.

Little is known about the reproductive activities of baiji. Ovulation in females is periodic and sperm density in males varies seasonally. The mating season peaks twice a year, in spring and in autumn. The gestation period estimates range from 6 to 12 months. Females give birth to one 80 cm long calf every two years. Baiji reach sexual maturity at 3 to 8 years of age.

Breeding interval: Female baiji breed once every two years.

Breeding season: The mating season peaks twice a year, in spring and in autumn.

Range number of offspring: 1 to 1.

Range gestation period: 6 to 12 months.

Range age at sexual or reproductive maturity (female): 3 to 8 years.

Range age at sexual or reproductive maturity (male): 3 to 8 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average number of offspring: 1.

Mothers carry their calves close to the side of their bodies while swimming, diving, and coming up to breathe. It is unknown how long they nurse their young, and whether there is any association between mother and offspring after the young are weaned.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)