No effect of delivery on total hip replacement survival: a nationwide register study in Finland.

Background and purpose - Previous small studies have suggested that delivery does not adversely affect the survivorship of total hip replacement (THR). We investigated whether delivery after primary THR affects hip implant survivorship in a large population-based study sample Patients and methods - In this register-based nationwide cohort study, all women aged 15-45 who underwent primary THR in Finland from 1987 to 2007 were included from the Finnish Arthroplasty Register. Data on deliveries were obtained from the medical birth register. After primary THR, 111 women (133 THRs) delivered and formed the delivery group. In the reference group, 1,878 women (2,343 THRs) had no deliveries. We used Kaplan-Meier analysis with 95% confidence intervals (CI) to study implant survivorship at 6 and 13 years, and Cox multiple regression to assess survival and hazard ratios (HRs), with revision for any reason as an endpoint with adjustment for age, rheumatoid arthritis, and stem and cup fixation. Results - 51 (38%) revisions were recorded in the delivery group and 645 (28%) revisions in the reference group. The 6-year implant survivorship was 91% (CI 85-96) in the delivery group and 88% (CI 87-90) in the reference group. The 13-year survival rates were 50% (CI 39-62) and 61% (CI 59-64). The adjusted HR for revision after delivery was 0.7 (CI 0.4-1.2) in ≤ 6.8 years' follow-up and 1.1 (CI 0.8-1.6) in > 6.8 years' follow-up. Interpretation - Based on the findings in this nationwide study of hip replacement in fertile-aged women, delivery does not seem to decrease THR implant survivorship; women should not be afraid of or avoid becoming pregnant after THR.