The frequency of misattributed paternity in Sweden is low and decreasing: A nationwide cohort study

The occurrence of misattributed paternity has consequences throughout society with implications ranging from inheritance and royal succession to transplantation. However, its frequency in Sweden is unknown.

To estimate the contemporary frequency of misattributed paternity in Sweden.

The study was based on nationwide ABO blood group data and a nationwide register of familial relationships in Sweden. These data were analysed using both a frequentist Poisson model and the Bayesian Gibbs model. The conduct of the study was approved by the regional ethics committee in Stockholm, Sweden (reference numbers 2018/167-31 and 2019-04656).

Nearly two million mother-father-offspring family units were included. Overall, the frequency of misattributed paternity was estimated at 1.7% in both models. Misattributed paternity was more common among parents with low educational levels, and has decreased over time to a current 1%.

The misattributed paternity rate is similar to the rates in other West European populations. Apart from widespread societal implications, studies on heritability may consider misattributed paternity as a minor source of error.