Amniotic Fluid Embolism Induces Uterine Anaphylaxis and Atony following Cervical Laceration

Abstract

Amniotic fluid embolism (AFE) is a rare, high-risk obstetric complication primarily found in the lungs and potentially related to anaphylaxis. Tryptase release from the mast cell reflects anaphylaxis. Case report and findings: A female, aged over 40 years, presented with uterine atony and lethal hemorrhage after induced vaginal labor. Cervical laceration was accompanied by severe hemorrhage. Stromal edema and myometrial swelling were consistent with uterine atony. Alcian blue staining and zinc coproporphyrin immunostaining disclosed AFE, which was more prominent in the uterus than in the lungs. Tryptase immunostaining was diffuse and prominent around the activated mast cells (halos) in the uterus, including the cervix. Similar distribution of findings on the AFE markers, tryptase halos, complement receptor C5aR, and atony in the uterus suggested the causality of AFE to anaphylaxis, complement activation and atony. It is probable that disseminated intravascular coagulation (DIC), induced by AFE, uterine atony and cervical laceration, caused the lethal hemorrhage. It is likely that AFE, in association with cervical laceration, induces uterine anaphylaxis, complement activation, atony, DIC and lethal hemorrhage.

Amniotic fluid embolism: Pathophysiology from the perspective of pathology

“…Immunohistochemical techniques also revealed an increased count of CD88‐positive cells within the uterine stroma, prominent tryptase halos around activated mast cells, elastase‐positive neutrophils, and CD68‐positive macrophages in the myometrium of DIC type PPH (Fig. a‐d) . Increased CD88 immunostaining of inflammatory cells was found to be related to the edematous stroma and swollen myometrium, suggesting an association between complement activation and inflammation as well as uterine atony .…”

“…a‐d) . Increased CD88 immunostaining of inflammatory cells was found to be related to the edematous stroma and swollen myometrium, suggesting an association between complement activation and inflammation as well as uterine atony . We proposed these features of “Postpartum acute myometritis (PAM)” as a histological character in PPH of unknown etiology secondary to uterine atony, widely regarded as uterine‐type AFE (Fig.…”

“…An anaphylactoid reaction refers to the non‐immune‐mediated degranulation of mast cells, different from anaphylaxis, which is IgE‐mediated hypersensitivity . To date, immune cell activation induced through complement activation and mast cell‐mediated anaphylactoid reaction have been proposed as potential pathophysiological mechanisms . Some women may tolerate the transfer of amniotic fluid or its components with no problems if an anaphylactoid reaction is adequately prevented by biological inhibitors such as the C1 inhibitor .…”

Amniotic fluid embolism

“…As a result, Clark et al [16] proposed the term 'Anaphylactoid Syndrome of Pregnancy' -an entity that has some commonality with the systemic inflammatory response syndrome. The most often suspected sites of amniotic fluid entry are the endocervix and the lower uterine segment, with endocervical veins, uterine trauma sites, and the placental attachments likely involved in the egress of fetal tissue [17].…”

Amniotic Fluid Embolism

“…Anaphylaxis is the most frequently recorded symptoms and also associated with complement activation. More recently, Tamura et al 40 reported that AFE can induce uterine atony, DIC, and lethal hemorrhage possibly through anaphylaxis and complement activation. The clinical symptoms differ according to the subtypes of AFE.…”