A sufficient number of participants made it possible to evaluate the three subgroups of obesity suggested by World Health Organization (obesity class I–III). The drawback is the sometimes low validity of information. ICD codes have been used to define various types of postpartum hemorrhage. It is obvious, given the large size of the study and the numbers of health care units involved, that the criteria for diagnosis may not be uniform across the study population, but the variation is probably not related to maternal BMI.