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Since the publication of the article, it has come to the authors’ attention that the flowchart (Figure 1) can be misleading. According to the flow chart, 1 738 358 pregnancies ending as an abortion were excluded due to missing gestational age or gestational age >140 days. This seems to be a large proportion of missing data, which could question the validity of the coding of abortions in the patient registry. It was, however, not at missing data problem but was due to technical reasons. In the raw data, a unique abortion could be recorded more than once. Removing duplicates is therefore a regular part of the data cleaning process when working with these data. In our data, 1 733 799 abortions were removed because they were duplicates, which would have been the correct designation in the flow chart rather than missing gestational age. Of notice, the final number of pregnancies included in the analyses was correct.
Anne Staub Rasmussen
Christian Fynbo Christiansen,