Need for developing case definitions, and guidelines for data collection, analysis, and presentation for antenatal bleeding as an adverse event:
Bleeding in the second and third trimesters of pregnancy affects 6% of all pregnancies, and has distinct etiologies from first-trimester bleeding [1]. In the vast majority of cases, antenatal bleeding is vaginal and obvious; however, rarely, it may be contained within the uterine cavity, the intraperitoneal space, or the retroperitoneal space. The etiologies of antenatal bleeding, also referred to as antepartum hemorrhage, are heterogeneous. In cases of severe antepartum hemorrhage, complications include preterm delivery, cesarean delivery, blood transfusion, coagulopathy, hemodynamic instability, multi-organ failure, salpingectomy/oophorectomy, peripartum hysterectomy, and in some cases, either perinatal or maternal death.
The goal of this Working Group was two-fold:
(1) to define sources of pathologic antenatal bleeding in the second or third trimester of pregnancy that are directly attributable to pregnancy and are either common and/or catastrophic;
(2) to define each source of antenatal bleeding for the purposes of future case ascertainment.
The charge to the Brighton Collaboration Working Groups to define various adverse obstetric and pediatric events includes an aim to more easily identify immunization-related adverse events. In the case of antenatal bleeding, our Working Group felt strongly that there is no biologic plausibility or mechanistic explanation linking immunizations to antenatal bleeding. Moreover, as immunizations and antenatal bleeding are common occurrences in the course of any individual pregnancy, it is quite likely that these events will co-occur without suggesting causation. To date, there is one case report of antenatal bleeding occurring in a pregnancy where a tetanus, diphtheria, and acellular pertussis vaccination was also administered [2]. However, the definition used to identify the antenatal bleeding event is not clearly presented. Standardized definitions across trials, surveillance systems, or clinical settings will facilitate case ascertainment and analysis of potential risk factors for antenatal bleeding.
In this document, we focus on placenta previa, morbidly adherent placentation, vasa previa, placental abruption, cesarean scar pregnancy, intra-abdominal pregnancy, and uterine rupture as important sources of antenatal bleeding. Cesarean scar pregnancy and intra-abdominal pregnancy are rarely listed as causes of antenatal bleeding in the second and third trimester. Nonetheless, we included these causes as they are more likely to result in late presentation with a high risk of heavy maternal bleeding in settings in which ultrasound diagnosis of pregnancy is limited or unavailable.
Another common source of bleeding is labor, whether at term or preterm. Although preterm labor is pathologic and addressed in another document [3], bleeding in the context of labor alone is not. This is not addressed in our document. Non-obstetric genital tract bleeding may also occur during pregnancy, including neoplastic, infectious, traumatic, or iatrogenic causes. Urinary tract infections or hemorrhoids may also be misidentified as antenatal bleeding until additional workup is performed. This document will focus solely on the pregnancy-attributable etiologies of antenatal bleeding.
