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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Miscarriage = spontaneous pregnancy loss <24 weeks. Most common in first trimester
- Types: threatened (bleeding, os closed, viable fetus), inevitable (os open, ongoing), missed (fetal demise, os closed, no symptoms), incomplete (partial tissue passage), complete
- USS criteria for non-viability: CRL ≥7 mm with no heartbeat, or mean sac diameter ≥25 mm with no embryo
- Management options: expectant (wait), medical (vaginal misoprostol ± mifepristone), or surgical (MVA/ERPC)
- Progesterone (400 mg micronised vaginal BD) offered for threatened miscarriage with previous miscarriage and confirmed IUP
- Recurrent miscarriage (≥3): investigate for antiphospholipid syndrome, uterine anomalies, and thrombophilia
Overview
Miscarriage is the spontaneous loss of a pregnancy before 24 weeks of gestation. It is the most common complication of early pregnancy, with the majority occurring in the first trimester. The causes are multifactorial but chromosomal abnormalities (particularly trisomies) account for at least 50% of first-trimester losses. Miscarriage is classified by the clinical presentation: threatened (viable pregnancy with bleeding), inevitable (open os, loss in progress), missed (fetal demise without symptoms), incomplete (partial passage of products), and complete.
Epidemiology
Approximately 1 in 4 recognised pregnancies ends in miscarriage. The risk is highest in the first 12 weeks, declining significantly after a viable heartbeat is seen on scan. Risk increases with maternal age: ~10% at age 20–24, ~50% at age 40+. Other risk factors include previous miscarriage, smoking, excessive alcohol, obesity, caffeine intake >200 mg/day, uterine anomalies, antiphospholipid syndrome, and poorly controlled diabetes or thyroid disease. Recurrent miscarriage (≥3 consecutive losses) affects approximately 1% of couples.
Clinical Features
Symptoms
Vaginal bleeding — the most common symptom, ranging from spotting to heavy bleeding with clots
Suprapubic or lower abdominal cramping pain
Passage of tissue or products of conception per vagina
Disappearance of pregnancy symptoms (missed miscarriage)
Heavy bleeding with haemodynamic compromise
Fever, rigors, offensive discharge (suggesting septic miscarriage)
Signs
Threatened: cervical os closed, uterus appropriate size, active bleeding
Inevitable: cervical os open, active bleeding, products may be visible
Missed: uterus may be smaller than dates, os closed, no active bleeding
Incomplete: os open, uterus smaller than expected, ongoing bleeding
Signs of sepsis: pyrexia, tachycardia, uterine tenderness, offensive discharge
Investigations
First-line
Transvaginal ultrasoundKey investigation. Non-viability: CRL ≥7 mm with no heartbeat, or mean sac diameter ≥25 mm with no embryo. If uncertain, repeat scan in ≥7 days
Serum beta-hCGFor pregnancy of unknown location or when USS inconclusive. Serial measurements 48 h apart
FBCAssess haemoglobin if significant bleeding
Second-line
Group and saveIf surgical management planned or significant haemorrhage. Check Rh status
Urine pregnancy test at 3 weeksAfter medical or expectant management to confirm complete miscarriage
Specialist
Recurrent miscarriage investigationsAntiphospholipid antibodies (lupus anticoagulant, anticardiolipin, anti-beta-2 glycoprotein), thrombophilia screen, pelvic USS for uterine anomalies, thyroid function, cytogenetics of products
1
Threatened miscarriage
- Reassurance if viable IUP on scan — majority will continue to term
- Offer vaginal micronised progesterone 400 mg BD if previous miscarriage AND confirmed IUP on scan — continue until 16 weeks
- Advise to return if bleeding worsens or pain develops
- No evidence that bed rest improves outcome
2
Expectant management
- Appropriate for confirmed miscarriage in a clinically stable woman
- Wait for natural expulsion — successful in ~50% at 2 weeks for incomplete, less for missed miscarriage
- Provide urine pregnancy test to perform at 3 weeks — negative confirms complete miscarriage
- Safety-netting: return if heavy bleeding, fever, or persistent positive pregnancy test at 3 weeks
3
Medical management
- Missed miscarriage: mifepristone 200 mg oral followed 48 hours later by misoprostol 800 mcg vaginal
- Incomplete miscarriage: misoprostol 600 mcg oral (single dose)
- Provide analgesia (NSAIDs, paracetamol, codeine) and anti-emetics
- Urine pregnancy test at 3 weeks post-treatment
4
Surgical management
- Manual vacuum aspiration (MVA) under local anaesthetic — can be performed in outpatient setting
- Surgical management under general anaesthetic (ERPC/SMM) if patient preference or medical management has failed
- Anti-D immunoglobulin if Rh-negative and >12 weeks gestation or surgical management at any gestation
Complications
- Haemorrhage: Heavy bleeding may require resuscitation and emergency surgical evacuation
- Infection: Septic miscarriage — fever, uterine tenderness, offensive discharge. Requires IV antibiotics and urgent evacuation
- Retained products: After incomplete miscarriage — ongoing bleeding, risk of infection
- Psychological: Grief, anxiety, depression — offer support, counselling, and signpost to charities (Miscarriage Association, Tommy's)
- Asherman syndrome: Rare — intrauterine adhesions after repeated instrumentation
UKMLA Exam Tips
- 1Missed miscarriage = fetal demise but os CLOSED, no symptoms. CRL ≥7 mm with no heartbeat on USS
- 2Inevitable miscarriage = os OPEN with active bleeding. Key distinction from threatened (os CLOSED)
- 3Progesterone for threatened miscarriage ONLY if previous miscarriage AND confirmed IUP on scan
- 4Mifepristone + misoprostol for missed miscarriage. Misoprostol alone for incomplete miscarriage
- 5Anti-D required for Rh-negative women: surgical management at any gestation, or any management >12 weeks
- 6Recurrent miscarriage (≥3): test for antiphospholipid syndrome — treat with aspirin + LMWH in future pregnancies
practicetest your knowledge on miscarriageApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — obstetrics and beyond.
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