Introduction
Miscarriage is the most common complication of early pregnancy, affecting an estimated 1 in 5 clinically recognised pregnancies. For clinicians in the UK, two key bodies provide evidence-based guidance for its management: the National Institute for Health and Care Excellence (NICE) and the Royal College of Obstetricians and Gynaecologists (RCOG). The NICE guideline (Ectopic pregnancy and miscarriage: diagnosis and initial management, NG126, last updated April 2024) provides a comprehensive national standard. The RCOG Green-top Guideline (The Management of Early Pregnancy Loss, No. 25, October 2023) offers specialist obstetric and gynaecological perspective. This comparison aims to delineate the recommendations from these two authoritative sources, highlighting areas of alignment and divergence to inform clinical practice in the UK in 2025.
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Diagnosis and Assessment
Confirming Pregnancy Viability
Both guidelines are aligned on the fundamental principles of using transvaginal ultrasound (TVS) and serial human chorionic gonadotropin (hCG) measurements to diagnose miscarriage. Key consensus points include:
- Ultrasound Criteria: A mean gestational sac diameter of ≥25 mm with no fetal pole, or a fetal pole with a crown–rump length (CRL) of ≥7 mm with no fetal heart activity, are definitive criteria for miscarriage.
- Serum hCG: Used when ultrasound findings are inconclusive, with an emphasis on the importance of a 48-hour interval for repeat testing to interpret the trend.
Key Differences in Diagnostic Approach
- First-Trimester Pregnancy Location: NICE is more cautious, stating that the diagnosis of miscarriage should not be made on a single TVS if the pregnancy is in the uterus but the crown–rump length is less than 7.0 mm with no heartbeat, or the mean sac diameter is less than 25.0 mm with no fetal pole. A second scan at least 7 days later is recommended.
- RCOG's Pragmatic Stance: While agreeing with the need for caution, RCOG provides more nuanced guidance for scenarios where a pregnancy is likely to be failing but does not yet meet the strict criteria. It discusses the use of a "probable diagnosis" of early pregnancy loss to facilitate shared decision-making about expectant management or treatment, while still adhering to the definitive criteria for intervention.
- Terminology: RCOG uses the term "Pregnancy of Unknown Location (PUL)" more frequently and provides a detailed management algorithm, whereas NICE integrates PUL management within its broader ectopic pregnancy guidance.
Practical Takeaway: NICE provides a stricter, more conservative protocol to avoid the rare but catastrophic error of terminating a viable pregnancy. RCOG offers a framework for managing clinical uncertainty that may be more reflective of day-to-day practice in early pregnancy assessment units (EPAUs).
Treatment Options and Management
Both guidelines endorse the three main management options: expectant, medical, and surgical. The emphasis is on providing women with a choice after a balanced discussion of the benefits and risks.
Expectant Management
- NICE recommends offering expectant management for 7–14 days as a first-line option for women with a confirmed miscarriage.
- RCOG concurs but provides more detailed guidance on counselling, including expected symptoms (pain, bleeding) and the potential for prolonged follow-up.
Medical Management
- Drug Regimen: Both recommend vaginal misoprostol as the preferred route. The dosage is aligned: 800 micrograms for missed or incomplete miscarriage.
- Key Difference: NICE provides specific guidance on a self-management pathway, suggesting that for suitable women, medical management can be administered at home without the need for hospital admission, with clear safety-netting advice. RCOG supports this approach but places it more within the context of a well-organised EPAU service.
Surgical Management (Uterine Evacuation)
- Manual Vacuum Aspiration (MVA): This is a significant area of divergence. RCOG strongly advocates for the use of MVA in an outpatient or clinic setting, highlighting its cost-effectiveness, speed, and patient satisfaction. It is presented as a first-line surgical option.
- NICE mentions MVA but does not promote it with the same emphasis, instead focusing more broadly on "uterine evacuation" generally performed in a theatre setting under general or local anaesthetic.
- RhD Prophylaxis: Both guidelines recommend anti-D immunoglobulin for RhD-negative women undergoing surgical management. RCOG extends this recommendation to medical management, whereas NICE, based on a different interpretation of the evidence, does not routinely recommend it for medical management unless the bleeding is heavy or there is a need for subsequent surgical intervention.
Practical Takeaway: The most prominent difference is RCOG's strong endorsement of outpatient MVA. Clinicians should be aware of this effective option. The difference in anti-D guidance for medical management is a key practical point that requires local protocol agreement.
Special Situations
Recurrent Miscarriage
This is managed under separate, dedicated guidelines from both organisations (NICE CG154 and RCOG GTG17). For the context of managing an acute miscarriage in a woman with a history of recurrent loss, both NG126 and RCOG GTG25 emphasise the need for sensitive care and clear referral pathways to specialist recurrent miscarriage services.
Complete Miscarriage
- NICE states that women with a complete miscarriage confirmed by TVS who are asymptomatic do not require further follow-up.
- RCOG agrees but adds a caveat about ensuring serum hCG has fallen to non-pregnant levels, particularly if there was any prior doubt about the pregnancy location (e.g., a previous PUL).
Later Miscarriage (14-24 Weeks)
RCOG provides more detailed guidance on the management of later miscarriages, including the use of mifepristone prior to misoprostol and specific protocols for induction. NICE's NG126 focuses primarily on first-trimester loss.
Practical Clinical Flow
A combined, pragmatic flow for a stable patient presenting to an EPAU would be:
- Presentation & Assessment: History, examination, TVS.
- Diagnosis: Apply strict NICE/RCOG criteria. If inconclusive, schedule repeat TVS in 7-14 days or serial hCG.
- Shared Decision-Making: Discuss all three options (expectant, medical, surgical), tailoring the discussion with insights from both guidelines (e.g., highlighting outpatient MVA as per RCOG, and home administration of misoprostol as per NICE).
- Management & Safety-Netting: Provide clear written information, pain relief, and instructions on when to seek urgent help (e.g., heavy bleeding, fever, severe pain).
- Follow-up: Arrange follow-up based on the chosen management strategy. Discharge asymptomatic patients with a confirmed complete miscarriage.
- Psychological Support: Both guidelines stress the importance of offering emotional support and information about support organisations like the Miscarriage Association.
Frequently Asked Questions (FAQs) for Clinicians
1. Which guideline takes precedence if there is a conflict?
NICE guidelines often form the basis for national service specifications and commissioning. However, RCOG guidelines represent the specialist standard of care. In practice, NHS Trusts develop local protocols that synthesise both. Where they differ (e.g., anti-D prophylaxis), the local protocol, ideally developed with input from both, should be followed.
2. How should I manage a woman who meets "probable" but not "definitive" criteria for miscarriage?
This is where RCOG's nuanced approach is helpful. You can discuss the high likelihood of pregnancy loss and offer expectant management or a planned follow-up scan. It is crucial to avoid language that suggests absolute certainty and to ensure the patient understands the reason for the wait.
3. Is outpatient Manual Vacuum Aspiration (MVA) a recommended service model?
Yes, strongly by RCOG. It is considered safe, effective, and patient-centred. NICE does not discourage it but is less prescriptive. Clinicians advocating for service development should use the RCOG guideline to support the implementation of outpatient MVA services.
4. What is the current evidence regarding anti-D in medical management?
The discrepancy stems from differing interpretations of the risk of sensitisation. RCOG errs on the side of caution, recommending it for all RhD-negative women. NICE concludes the risk is very low and does not recommend it routinely. Local haematology and obstetrics departments should agree on a consistent Trust-wide policy.
5. What follow-up is necessary after a complete miscarriage?
Both agree that asymptomatic women with a TVS-confirmed complete miscarriage do not need routine follow-up. However, ensure that any prior concerns about pregnancy location are resolved (e.g., a falling hCG) as per RCOG's emphasis. Always provide a clear route for re-referral if concerns arise.
Source Links
- NICE Guideline NG126: Ectopic pregnancy and miscarriage: diagnosis and initial management (Last updated April 2024).
- RCOG Green-top Guideline No. 25: The Management of Early Pregnancy Loss (Published October 2023).
- Miscarriage Association: A national charity offering support and information.