Ultrasound for miscarriage: what they look for

Ultrasound examination plays a key role in the diagnosis and management of early pregnancy losses: it confirms the presence of pregnancy within the uterine cavity, assesses the viability of the embryo, identifies anatomical causes and helps to distinguish intrauterine death from ectopic pregnancy. [1]

Transvaginal ultrasound imaging provides the highest sensitivity and resolution in the first trimester, including for small fertilized sacs and suspected borderline findings that require observation. [2]

In clinical practice, ultrasound is used not only for “diagnosis”, but also for planning tactics: waiting with repeat scanning, drug treatment, instrumental removal of tissue, or referral for additional studies to find the causes of repeated losses. [3]

In case of repeated pregnancy losses, the ultrasound assessment is expanded: in addition to confirming the loss, the structure of the uterine cavity, ovarian status, the presence of subchorionic hematomas, fibroids, polyps and signs of anatomical abnormalities that may affect gestation are assessed. [4]

The role of ultrasound in single and repeated pregnancy loss

Ultrasound primarily answers questions such as the location of the pregnancy, whether the embryo and heartbeat are present, whether the size is appropriate for the gestational age, and whether there are signs of a massive hematoma or uterine abnormality. This helps differentiate situations requiring urgent intervention from those where observation is appropriate. [5]

For recurrent pregnancy loss, ultrasound becomes a screening tool for anatomical factors: detection of submucous fibroids, intrauterine adhesions, polyps, and congenital anomalies (for example, uterine septum) changes further diagnostics and treatment tactics. [6]

Recommendations of current practice guidelines emphasize that in cases of two or more consecutive spontaneous abortions, a thorough examination of the mother and partner should be initiated; the role of ultrasound in this case is primary visualization and an indication of the need for further investigation methods. [7]

It is important to understand the limitations of the method: ultrasound does not always clearly determine the cause of miscarriage (for example, chromosomal abnormalities of the embryo), but it is indispensable for rapid clinical orientation, assessment of complications and selection of the next step. [8]

First Trimester Practical Protocol: How and When to Scan

A transvaginal examination is considered the optimal first choice for assessing early pregnancy, especially in cases of uncertain or early pregnancy, pain, or bleeding. Transvaginal access allows for more accurate measurements of the gestational sac and embryo. [9]

Often the algorithm looks like this: if the pregnancy test is positive and there are symptoms, perform a transvaginal ultrasound; if the visualization is inconclusive or the findings are borderline, repeat the examination in 7-14 days and/or compare with the dynamics of human chorionic gonadotropin. [10]

There is a set of threshold ultrasound criteria that allow for the diagnosis of intrauterine death with high reliability: absence of a heartbeat when the embryo length is greater than the established threshold, absence of an embryo when the ovum is of a certain size, etc. These thresholds are used by clinical guidelines to reduce the number of false diagnoses. [11]

In cases of unclear imaging, a combination of repeat scanning and serial human chorionic gonadotropin monitoring is appropriate; immediate and definitive intervention without confirmation may result in unnecessary termination of a viable pregnancy.[12]

Table 1. Common steps of the ultrasound protocol for suspected early pregnancy loss

Step	What is being done?	For what	Note
1	Transvaginal ultrasound	Confirm the location and presence of the embryo	For short terms it is preferable. [13]
2	Heart rate and CTE assessment	Assess viability	Threshold criteria are used for diagnosis.[14]
3	Repeat scan in 7-14 days	Eliminate borderline cases	Recommended for uncertain findings. [15]
4	Serial beta-human chorionic gonadotropin	Verification of pregnancy dynamics	Used in conjunction with ultrasound. [16]

Ultrasound diagnostic criteria for infertility and borderline cases

Current guidelines define clear ultrasound criteria for diagnosing fetal death: for example, the absence of a heartbeat when the embryo is greater than 7 mm in length during transvaginal examination is considered a sign of intrauterine death. These thresholds help avoid premature conclusions. [17]

In the case of an empty ovum (anembryony, "blighted ovum"), the decision is based on the size of the ovum relative to time: if the ovum reaches the threshold and the embryo is not visualized on repeat scanning, the diagnosis is made. If the size is small, repeat observation is recommended. [18]

Subchorionic hematoma is common on ultrasound and does not always lead to pregnancy loss, but its size and dynamics are associated with an increased risk. Ultrasound helps classify the hematoma and guide decisions on follow-up and related measures. [19]

Differential tasks include exclusion of ectopic pregnancy and molar pregnancy; if extrauterine localization is suspected, a comprehensive approach is required, including serial hormone analyses and, if necessary, additional imaging methods. [20]

Table 2. Ultrasound findings and their clinical interpretation

Find	What could this mean?	Clinical importance
Absence of heartbeat with CTE >7 mm	Intrauterine death	Indicates an irreparable loss. [21]
Empty fertilized egg with large sizes	Anembryony	Requires confirmation and discussion of tactics. [22]
Subchorionic hematoma	Threat of miscarriage, the risk depends on the volume	Dynamic control is needed. [23]
No localization with a positive test	Pregnancy of unknown location	Suspected ectopic pregnancy. [24]

Ultrasound's search capabilities in relation to the uterus and appendages

Ultrasound can detect structural uterine abnormalities associated with an increased risk of recurrent pregnancy loss, including uterine septation, bicornuate uterus, and intrauterine adhesions. Additional imaging is often required for accurate verification. [25]

A detailed assessment includes the nature of the uterine cavity, the contours of the endometrium, and the presence of submucosal fibroids and polyps. Transvaginal sonography and sonohysterography with saline improve the accuracy of detecting intracavitary lesions. [26]

Fibroids, especially submucosal ones, and intrauterine polyps can interfere with implantation and lead to repeated losses; if significant changes are detected, ultrasound refers to surgery or hysteroscopic examination. [27]

If there is a suspicion of differentiation of the uterine septum and area form of anatomical variation, 3D ultrasound or magnetic resonance imaging is often used to clarify and plan possible correction. [28]

Table 3. Structural abnormalities of the uterus detected by ultrasound and possible steps

Anomaly	What does it look like on ultrasound?	What is recommended next?
Septum of the uterus	A longitudinal septum dividing the cavity	3D ultrasound or MRI, hysteroscopy if indicated. [29]
Submucosal fibroids	Protrusion into the uterine cavity	Hysteroresection for symptoms or RPL. [30]
Endometrial polyps	Foci in the cavity with a characteristic echostructure	Sonohysterography, hysteroscopy. [31]
Intrauterine adhesions	Uneven cavity, adhesions	Hysteroscopic removal, followed by observation. [32]

Additional visualization methods and their place

If ultrasound results do not provide a complete answer, additional methods are used: 3D ultrasound reconstruction, sonohysterography, hysteroscopy, and, if indicated, magnetic resonance imaging. The choice is based on the clinical question and the required accuracy. [33]

Saline-assisted sonohysterography improves visualization of the uterine cavity and more frequently detects polyps and submucosal fibroids compared with conventional transvaginal examination.[34]

Hysteroscopy remains the "gold standard" for diagnosis and immediate treatment of intracavitary processes; it is often used in cases of recurrent losses when ultrasound has revealed suspicious intracavitary changes. [35]

Magnetic resonance imaging is rarely used but is useful in complex anatomical dilemmas, such as to clarify the configuration of the uterus before planning septum correction.[36]

Table 4. Additional methods and their clinical application

Method	What clarifies	When to recommend
3D ultrasound	The exact shape of the uterine cavity	If a septum is suspected. [37]
Sonohysterography	Uterine cavity, polyps, submucosal fibroids	If the results of TV ultrasound are unclear. [38]
Hysteroscopy	Diagnosis and removal of intracavitary formations	In case of detected lesions and RPL. [39]
MRI	Complex structural anomalies	For preoperative planning. [40]

How ultrasound influences treatment decisions and monitoring plans

A diagnosis obtained via ultrasound determines the treatment plan: if intrauterine death is confirmed, options include expectant management, medical termination, or instrumental removal. The decision is made by the physician, taking into account the patient's condition and preferences. [41]

If ultrasound shows borderline, inconclusive features, repeat imaging after 7-14 days and serial determination of pregnancy hormone levels are often used to avoid erroneous premature intervention.[42]

In cases of repeated pregnancy losses, detection of anatomical pathology on ultrasound leads to consideration of correction: removal of polyps, hysteroscopic restoration of the cavity, and, if necessary, resection of the septum. The effect of such interventions on the outcome of subsequent pregnancies is assessed in guidelines and studies. [43]

Finally, ultrasound is used both in preoperative preparation and in monitoring after the intervention - assessment of the restoration of the uterine cavity, exclusion of relapse and preparation for planning a new pregnancy. [44]

Table 5. Tactical options depending on the ultrasound finding

Finding on ultrasound	Possible tactics	Comment
Confirmed intrauterine death	Choice between waiting, drug or instrumental treatment	Take into account the patient's condition and wishes. [45]
Borderline results	Repeat ultrasound in 7-14 days and serial tests	Eliminates false diagnoses. [46]
Structural pathology of the uterus	Planning hysteroscopy or other correction	May improve the chances of subsequent pregnancy.[47]

Practical recommendations for clinicians and patients

Clinicians should document all key ultrasound parameters: gestational sac size, parietal-crown diameter, presence or absence of a heartbeat, hematoma volume and location, and uterine cavity status. A complete record facilitates subsequent management and interdisciplinary discussions. [48]

When communicating with the patient, it's important to explain that ultrasound is informative, but not all-powerful: some causes of pregnancy loss are hidden at the cellular or chromosomal level and are not visible on an image. Providing support and planning further testing reduces anxiety and facilitates shared decision-making. [49]

When organizing a screening for women with recurrent pregnancy losses, a multidisciplinary approach is recommended: ultrasound assessment is combined with genetic, hormonal, and immunological testing in accordance with current recommendations. This approach increases the chances of identifying the cause and appropriate treatment. [50]

Finally, it is important to apply current standards for the interpretation of ultrasound findings and not to rush to definitive conclusions with borderline data; repeat examinations and combined assessment reduce the risk of erroneous clinical decisions. [51]

Table 6. Control parameters for recording and transfer to the medical record

Parameter	Description	Why is it important?
Size of the fertilized egg	In millimeters	To monitor the dynamics and make decisions. [52]
Cronoparietal size	In millimeters	Determines the viability of the embryo. [53]
Presence of a heartbeat	Yes or no	Key marker of viability. [54]
Presence of subchorionic hematoma	Volume and localization	Affects the prognosis. [55]
Anomalies of the uterine cavity	Description and suspicions	Referrals for further research. [56]

Conclusion

Ultrasound will remain the cornerstone of diagnostic workup for early pregnancy loss. Its strength lies in rapid visualization, assessment of viability, and identification of anatomical factors influencing outcomes. Accurate threshold criteria, careful use of repeat scans, and combination with hormonal and laboratory diagnostics remain key. [57]

For women with recurrent pregnancy losses, ultrasound is the starting point for a complete examination; identifying and, if necessary, correcting structural changes in the uterus improves the prognosis in subsequent pregnancies. Current guidelines call for a multidisciplinary approach and individualized management. [58]