Here we analysed rare and acute complications of endometriosis in pregnant women by searching Cochrane, HINARY, and PubMed databases. Keywords were “rare”, “causes”, “acute”, “complications”, “endometriosis”, and “pregnancy”. The search depth was 10 years (2011−2021). In total, we found 126 publications, 41 of which met the selection criteria. The course of pregnancy and childbirth in patients with endometriosis is insufficiently studied. Yet, it is characterised by a higher risk of complications including those rarely occurring: haemoperitoneum, intestinal perforation, appendicitis, torsion and rupture of the endometrioid cyst, and thoracic endometriosis. Because of major hormonal changes occurring during the pregnancy, endometriosis undergoes a significant progression or decidualisation. As endometrioid tissue is characterised by a resistance to progesterone, its defciency during the pregnancy can lead to necrosis, perforation of decidualised foci, and severe bleeding. Progesterone deficiency provokes hypervascularisation of the endometrioid tissue, which is the most common cause of spontaneous haemoperitoneum and most frequently occurs in the third trimester of pregnancy and after in vitro fertilisation. Pregnancy increases the risk of endometriosis-related intestinal perforation of different localisation: small intestine, caecum, appendix, and rectosigmoid colon. Limited information about the pregnancy-related complications of endometriosis leads to their underestimation, albeit they can be life-threatening and significantly impact the health of the mother and fetus. The results of this review indicate the need for the further studies of the pregnancy course in patients with endometriosis, especially after the use of assisted reproductive technology. Development of specific clinical guidelines would contribute to the efficient prevention of obstetric and perinatal complications in patients with endometriosis.