Decidual Bleeding as a Cause of Spontaneous Hemoperitoneum in Pregnancy and Risk of Preterm Birth.

BACKGROUND Spontaneous hemoperitoneum in pregnancy (SHiP) is a rare, life-threatening event, particularly relevant to women with endometriosis or deciduosis. METHODS To determine the type of lesions leading to SHiP, a literature search was conducted among all published SHiP cases. From a total of 1,339 publications, information on pathological findings at the bleeding site with histological data was found in 24 case reports (16 pregnant, 8 postpartum). RESULTS Among pregnant women (81% primigravida), 75% had a diagnosis of endometriosis and 25% of deciduosis. Among postpartum women (38% primiparous), 63% had a diagnosis of deciduosis and 25% of endometriosis. In all cases except one, decidual cells, with or without glandular structures, were present at the bleeding site. Decidual vessels were described in 7 cases and all exhibited vascular changes, including distension of the lumen, medial disorganization, or loss of vascular integrity. These vessels were significantly different from arteries seen in the secretory endometrium, showing that structural modifications take place during the initial stage of the remodelling of placental bed spiral arteries. CONCLUSIONS During pregnancy, a link seems to exist between ectopic decidualization, particularly that occurring in endometriotic foci, and occurrence of SHiP. In addition, subclinical decidual bleeding may be a potential risk factor for preterm labour.