From the Guidelines
A silent miscarriage without bleeding is typically characterized by the absence of fetal cardiac activity in an embryo measuring 7mm or larger on transvaginal ultrasound, as well as other findings such as an empty gestational sac measuring greater than 25mm in diameter, a yolk sac without an embryo, or a crown-rump length smaller than expected for gestational age. According to the most recent and highest quality study, the Society of Radiologists in Ultrasound consensus conference recommendations 1, the ultrasound findings characteristic of a silent miscarriage with no bleeding can be categorized into five main categories: concerning for early pregnancy loss (EPL), diagnostic of EPL, EPL in progress, incomplete EPL, and completed EPL. Some key findings include:
- Embryonic crown-rump length (CRL) <7 mm and no cardiac activity
- Mean sac diameter (MSD) 16-24 mm and no embryo
- Absence of embryo with cardiac activity 7-13 days following visualized gestational sac (GS) and no yolk sac (YS)
- CRL ≥27 mm and no cardiac activity
- MSD ≥25 mm and no embryo
- Absence of embryo with cardiac activity ≥14 days after visualization of GS and no YS These findings are based on transvaginal ultrasound (TVUS) criteria, which are considered the most accurate for diagnosing early pregnancy loss 1. It's worth noting that enhanced myometrial vascularity (EMV) may be present, but it should not be confused with other rare entities such as arteriovenous fistula (AVF) 1. Serial ultrasounds 7-10 days apart are often needed to confirm the diagnosis, especially in early pregnancy when dates may be uncertain. Once confirmed, management options include expectant management, medical management with misoprostol, or surgical evacuation depending on patient preference and clinical circumstances.
From the Research
Ultrasound Findings in Silent Miscarriage with No Bleeding
- The diagnosis of a silent miscarriage, also known as a missed abortion, is typically made after two ultrasound examinations, performed at least one week apart, showing no fetal heartbeat or embryonic development 2.
- On ultrasound, a silent miscarriage may appear as a gestational sac with no embryonic pole or fetal heartbeat, or an embryonic pole with no fetal heartbeat 3, 4.
- The ultrasound findings may also include a small gestational sac, or an irregularly shaped sac, with or without a yolk sac or fetal pole 4.
- In some cases, the ultrasound may show a non-viable pregnancy with a crown-rump length (CRL) of less than 33mm, and no fetal heartbeat 3.
Characteristics of Silent Miscarriage on Ultrasound
- The mean diameter of the gestational sac may be smaller than expected for the gestational age 4.
- The shape of the gestational sac may be irregular, and the sac may be empty or contain a small amount of debris 4.
- There may be no visible yolk sac or fetal pole, or these structures may be small and irregular 4.
- The ultrasound may also show a thickened endometrium, indicating a non-viable pregnancy 5.
Predictors of Complete Miscarriage
- Gestational age, crown-rump length, and gestational sac diameter are independent predictors of success of expectant management in women with silent miscarriage 4.
- The likelihood of complete miscarriage increases with increasing gestational age and crown-rump length, and decreases with increasing gestational sac diameter 4.
- Misoprostol treatment is successful in approximately 80% of cases, but no variable has been found to predict success of misoprostol treatment 4.