Quantification of the size of subchorionic hematoma causing pregnancy-related complications: a retrospective cohort study

Purpose This study aimed to establish criteria for defining "large" subchorionic hematoma (SCH) and assess its association with pregnancy complications. Method This was a retrospective cohort study conducted at our institution between 2019 and 2020. We compared the size of SCH between the pregnancy-related complication and non-complication groups, using two measurement methods. Receiver operating characteristic (ROC) curve analysis determined cutoff values. Additionally, we compared the occurrence of pregnancy complications among three groups: large SCH group (above the cutoff value), non-large SCH group (below the cutoff value), and non-SCH group. Results Of 1305 singleton pregnancies managed during the study, 80 cases were diagnosed with SCH. Pregnancy complications occurred in 15 patients. The patients with pregnancy complications had significantly larger SCH sizes with both measurement methods. For each method, the cutoff values calculated from the ROC curve analysis were as follows: Method 1, 25% (area under the ROC curve [AUC], 0.662); Method 2, 30% (AUC, 0.624). In Method 1, we found a significantly higher occurrence of preterm delivery in the large SCH group (24.1%) than in the non-large SCH (4.2%) and non-SCH groups (5.3%; all p < 0.01). In Method 2, there was a significantly higher occurrence of preterm delivery in the large SCH group (33.3%) than in the non-large SCH (6.5%) and non-SCH groups (5.3%; all p < 0.01). Conclusion Large SCHs may indicate a high risk of pregnancy-related complications. Among these, recognizing and managing cases that exceed the aforementioned cutoff value as high-risk cases may be beneficial for reducing pregnancy complications.