A 32-year-old G3P1011 patient was followed for a history of loop electrosurgical excision procedure and short cervix in a previous pregnancy. Early transvaginal cervical length at 16 weeks was within normal limits. During a transvaginal ultrasound at 18 weeks of gestation, cervical length was noted to be 3.5 cm. Behind the cervix, amorphous particulate matter was visualized in the amniotic fluid. The matter appeared heterogeneous, wispy, and adjacent to the internal cervical os, but also abutting the edge of the posterior low-lying placenta ( Figure , A, yellow arrow; Video ). A triangulated anechoic area of placental edge separation was noted immediately inferior to it ( Figure , A, white arrow). The particulate matter was noted to be adherent to the placental edge in all views ( Figure , A; Video ). Initial diagnosis of sludge was considered given the location and history of the cervical procedure. However, given the characteristic heterogeneity with overall less echogenicity (compared with sludge as compared to sludge) ( Figure , C), characteristic motion ( Video ), adherence to the placental edge, and long cervix, a marginal placental hematoma (clot) was suspected.
The patient presented to the hospital at 18 4/7 weeks of gestation with complaint of painless vaginal spotting. This was her first report of bleeding in the pregnancy. Initial evaluation revealed no active bleeding on speculum examination and a cervical length of 2.8 cm. Point-of-care ultrasound revealed that the hematoma had now become a large clot overlying the area of the cervical os ( Figure , B). Approximately 16 hours later, the patient developed painful uterine contractions and profuse vaginal bleeding clinically compatible with placental separation. She was noted to be diaphoretic, tachycardic, and hypotensive. She was diagnosed with clinical “abruption” and emergently transfused. Ultrasound revealed intrauterine fetal demise, and the patient precipitously delivered. An intact placenta was delivered soon after the fetus. Placental gross pathology had small areas of hemorrhage ( Figure , D and E), without microscopic signs of abruption or inflammation ( Figure , F).
This case highlights the fact that not all particulate matter identified near the cervix is amniotic fluid sludge. The unique ultrasound appearance of the particulate matter prospectively identified in this case, along with the subsequent clinical course suggestive of abruption, lends itself to the diagnosis of intraamniotic hematoma as opposed to amniotic sludge. Properly differentiating between these two entities is important for optimal clinical care. Amniotic fluid sludge represents a collection of bacterial and inflammatory cells embedded in an amorphous material, consistent with microbial biofilm. The presence of sludge is a sign of infection or inflammation within the amniotic cavity and has been associated with an increased risk of spontaneous preterm birth, funisitis, and histologic chorioamnionitis. Visually, amniotic sludge appears as homogenous and mobile dense (echogenic) aggregates of particulate matter close to the internal cervical os. Importantly, sludge is usually accompanied by a short cervix. In contrast, intraamniotic hematoma is characterized by heterogeneity, less overall echogenicity, wispiness, and adjacency to placental edge separation, as seen in this case. As a key feature, intraamniotic hematoma usually occurs with normal cervical length.
Previous cases of subchorionic hematoma and “sludge” have been described, including a case similar to ours where the patient had normal cervical length, a hematoma that enlarged, and eventual progression to clinical abruption. Placental pathology did not show signs of infection or histologic confirmation of the subchorionic hematoma. Although there were no histologic signs of chorioamnionitis, both in our case and in this previously published case, it should be noted that intraamniotic bleeding has been associated with microbial invasion of the amniotic cavity in 14% of cases. We did not perform amniocentesis, which would fully rule out the diagnosis of intraamniotic infection or inflammation. However, based on sonographic appearance and clinical course, the particulate matter in our case was most consistent with intraamniotic hematoma. A study of 317 patients with intraamniotic hematoma found that it is related to impaired placentation, preterm labor, and miscarriage, with higher rates of stillbirth and total adverse outcome noted with increasing size of hematoma. Our patient progressed from sonographic suspicion for intraamniotic hematoma to clinical diagnosis of abruption within a few days, with maternal morbidity of hemorrhage and the worst perinatal outcome, midtrimester demise.
Although placental pathology did not show microscopic signs of abruption, this is not infrequently the case. A sensitivity of 30.2% of histologic confirmation for abruption has previously been reported. Because of the location of this intraamniotic hematoma at the placental edge and overlying the cervix, it is very likely that the hematoma detached and delivered first, separately from the remainder of the placenta. Previous reports of peripheral placental separation describe vascular abnormalities that predispose to ischemia of the decidua and placental abruption, thereby leading to premature delivery. This could be a contributing mechanism in this case. A previous study examining 90 placentas from patients with premature delivery found that 49 of them had evidence of antepartum marginal hemorrhage. Here, the ultrasound findings of marginal hematoma reinforce the clinical diagnosis of placental abruption, even without confirmation on pathology. Perhaps situations such as this one can explain the overall poor concordance between clinical and pathologic criteria for placental abruption. If the implicated blood clot separates prematurely and delivers ahead of the placenta, pathology would not necessarily confirm abruption on a microscopic level. However, the sonographic presence of an intraamniotic hematoma can help guide evaluation and management in future pregnancies.
Here in this case, the sonographic particulate matter in the amniotic fluid could have been mistaken for sludge without careful consideration of the matter’s exact characteristics and accompanying cervical length. Particulate matter that is heterogeneous, adherent to placental edge separation, and noted in the presence of normal cervical length is more likely to represent intraamniotic hematoma. Proper diagnosis of hematoma alerts the clinician to the possibility of developing abruption, thereby encouraging further monitoring and patient-specific care.
Supplementary Data
Cine of transvaginal ultrasound
Amorphous matter adjacent to the internal cervical os, abutting placental edge. Characteristic motion is seen, with irregular movement of multiple long wispy projections.
Kantorowska. Amniotic fluid sludge and blood clot from placental edge separation. Am J Obstet Gynecol 2022.
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