Key Facts

Miscarriage is defined as the spontaneous loss of a pregnancy before 24 weeks of gestation. It is the most common complication of early pregnancy. Early pregnancy assessment units (EPAUs) play a central role in diagnosis and management.

Epidemiology

• Affects approximately 25% of all recognised pregnancies
• 80% occur before 12 weeks gestation
• Incidence increases significantly with maternal age
• Chemical pregnancies (very early loss) are even more common but often unrecognised

Aetiology

• Chromosomal abnormalities: 50-60% of sporadic first-trimester miscarriages (trisomy most common, followed by monosomy X and triploidy)
• Maternal factors: advanced age, uterine anomalies (septate uterus), fibroids (submucosal), cervical incompetence
• Endocrine: poorly controlled diabetes, thyroid disease, PCOS
• Thrombophilia: antiphospholipid syndrome (most important treatable cause)
• Infection: bacterial vaginosis, TORCH infections
• Lifestyle: smoking, alcohol, cocaine, high caffeine intake (>300mg/day)

Pathophysiology

• Chromosomal abnormalities lead to abnormal embryo development and spontaneous expulsion
• Antiphospholipid syndrome causes placental thrombosis and infarction
• Cervical incompetence results in painless cervical dilatation typically in the second trimester
• Uterine anomalies impair implantation and placental development

Threatened Miscarriage

• Vaginal bleeding (usually light) with closed cervical os
• May have mild cramping
• Viable pregnancy on USS in 50% of cases

Inevitable Miscarriage

• Heavy vaginal bleeding with open cervical os
• Significant crampy lower abdominal pain
• Products of conception may be visible at the os

Incomplete Miscarriage

• Passage of some products of conception
• Continued bleeding and pain
• Open cervical os with retained tissue on USS

Missed Miscarriage

• Embryo has died but not yet expelled
• May have brown discharge or no symptoms
• Often diagnosed incidentally on USS
• CRL ≥7mm with no cardiac activity on TVS (NICE NG126)

Red Flags

• Heavy bleeding with haemodynamic compromise
• Signs of sepsis (septic miscarriage): fever, offensive discharge, tachycardia
• Severe abdominal pain (consider ectopic pregnancy)
• Products of conception at the cervical os (can cause vasovagal collapse - remove with sponge forceps)

Bedside

• Urine pregnancy test
• Observations: HR, BP, temperature
• Speculum examination: assess cervical os, exclude products at os

Bloods

• Serum βhCG: if diagnosis uncertain or pregnancy of unknown location
• FBC: assess for anaemia from blood loss
• Group and save: if significant bleeding
• Rhesus status

Imaging

• Transvaginal ultrasound: gold standard for diagnosis (NICE NG126)
  • Missed miscarriage: CRL ≥7mm with no cardiac activity
  • Empty sac: mean gestational sac diameter ≥25mm with no embryo (anembryonic pregnancy)
  • If findings are uncertain: repeat TVS in minimum 7 days

Special Tests

• Histology of products of conception (confirm pregnancy tissue, exclude molar pregnancy)
• Karyotyping of products if recurrent miscarriage

Non-pharmacological

• Expectant management: first-line for incomplete miscarriage; successful in 50% within 2 weeks
• Provide written information and 24-hour contact details
• Offer psychological support and follow-up
• If products at the cervical os: remove with sponge forceps (can cause vasovagal reaction)

Pharmacological

• Misoprostol 800mcg PV (or 600mcg PO) as a single dose: recommended if expectant management fails or patient preference
• Can repeat misoprostol dose after 48 hours if incomplete expulsion
• Analgesia: NSAIDs (ibuprofen 400mg TDS), paracetamol, codeine for pain
• Anti-D immunoglobulin: for RhD-negative women if surgical management at any gestation, or medical/expectant management if ≥12 weeks
• Antibiotics: if septic miscarriage (IV amoxicillin, metronidazole, and gentamicin)

Surgical/Interventional

• Manual vacuum aspiration (MVA): can be performed under local anaesthesia in outpatient setting
• Surgical management under general anaesthesia (ERPC): evacuation of retained products of conception
• Indications: patient choice, heavy persistent bleeding, signs of infection, failed medical management

Referral Criteria

• All women with bleeding in early pregnancy should be referred to EPAU (NICE NG126)
• Emergency referral if haemodynamically unstable or septic
• Refer for recurrent miscarriage investigation after 3 consecutive losses (or 2 if age >35)

• After a single miscarriage, chance of successful next pregnancy: 85%
• After two miscarriages: 75%
• After three miscarriages: 65%
• Risk of miscarriage by maternal age: 10% at age 20-24, 20% at age 35-39, 50% at age >45
• Septic miscarriage mortality: <1% with prompt treatment
• Psychological impact: significant; associated with anxiety and depression in subsequent pregnancies

Classification of Miscarriage

TVS Diagnostic Criteria (NICE NG126)