This retrospective cohort study assesses the incidences of major fractures and surgery in women during the puerperium and the lactation period in Finland between January 1, 1999, and December 31, 2018. Using nationwide data from the Finnish Care Register for Health Care and the Finnish Medical Birth Register, all women aged between 15 and 49 years with a fracture hospitalization within 12 months of delivery between 1999 and 2018 were included. During the study period, a total of 3140 fractures after delivery and 152,800 fractures of the female normal population of similar age were hospitalized. The incidence rate after delivery increased from 219/100,000 person-years during the first 4 months to 310 fractures/100,000 person-years during the latter 8 months of the first year after delivery. Altogether, 29% (n = 904/3140) of these fractures were treated operatively. The most common fractures were ankle and distal radius fractures, which made up one-third of all fractures. The incidence of pelvic fracture hospitalization was 15/100,000 person-years at 4 months after delivery, with an operation rate of 22%. Over half of all fractures occurred between 6 and 12 months after delivery (mean 6.6 months). The incidence of fracture hospitalization after delivery increased steadily during the puerperium and the lactation periods but remained lower than in the general population (age-adjusted incidence 554/100,000 person-years) with an incidence rate ratio of 0.51. However, a higher proportion of pelvic fractures were observed in the first months after delivery. Surgical rates were in line with the general population. Fractures of the wrist and ankle made up most of the fractures.