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Mr Parijat Bhattacharjee, Private Consultant Gynaecologist, Harrow, Brentford, Northwood, London, UK / Media / Videos » Recurrent Miscarriages: Causes

Recurrent Miscarriages: Causes

Recurrent Miscarriages: Causes
Posted on: 03-Jul-2026

This video, titled "Recurrent Miscarriages: Causes" by Gynae Consultant, addresses the medical definition of recurrent miscarriage, the foundational baseline risk factors, and explores both confirmed and suspected etiologies.

Definitions and Baseline Prevalence

  • Miscarriage: A pregnancy loss occurring before 24 weeks of gestation (the threshold of fetal viability in the UK).
  • Recurrent Miscarriage: Diagnostic criteria vary globally. In the UK, the Royal College of Obstetricians and Gynaecologists (RCOG) defines it as three consecutive losses, affecting about 1% of the population. The American Society for Reproductive Medicine (ASRM) defines it as two consecutive losses, which affects roughly 5% of the population.

Basic Risk Factors

  • Maternal Age: The risk rises drastically from around 11% in women under 25 to nearly 40% for women aged 40 and older.
  • Previous Losses: A history of multiple consecutive miscarriages directly elevates the statistical risk of a subsequent loss.
  • Lifestyle Factors: Observational data independent risk links include obesity, high alcohol intake, active or passive smoking, and excess caffeine consumption.

Confirmed and Suspected Etiologies

1. Genetic and Chromosomal Abnormalities

Accounting for 5% to 15% of recurrent miscarriages, these include structural translocations passed down by a parent:

  • Reciprocal Translocations: Balanced genetic exchanges where the parental carrier is healthy, but gametes run a 50% to 70% risk of unbalanced layouts, driving a high rate of miscarriage or congenital malformations.
  • Robertsonian Translocations: Centric fusions of chromosomes carrying a 3% to 6% risk of recurrent loss.

2. Thrombophilia (Blood Clotting Disorders)

Because pregnancy is a naturally hypercoagulable state to prevent maternal hemorrhage, excess clotting disorders drastically threaten placental function.

  • Acquired (Antiphospholipid Syndrome / APS): Found in 15% of recurrent miscarriage patients, APS causes placental inflammation and microthrombi (clots). Untreated, the live birth rate drops to 10%. It is diagnosed via clinical criteria (clots or specific pregnancy complications) alongside laboratory validation (Lupus Anticoagulant, Anti-Cardiolipin, or Anti-Beta-2 Glycoprotein-1 antibodies) positive on two tests 12 weeks apart.
  • Inherited Thrombophilias: Conditions like Factor V Leiden mutation, Prothrombin gene mutation, and Protein C, S, or Antithrombin III deficiencies are more strongly associated with late, second-trimester losses.

3. Anatomical and Endometrial Defects

  • Uterine Anomalies: Congenital structural anomalies occur in up to 37% of women with recurrent losses. Submucosal and large intramural fibroids can distort the cavity and hinder embryo implantation.
  • Asherman Syndrome: Intrauterine scar tissue resulting from surgery or infection accounts for roughly 10% of cases.
  • Cervical Incompetence: Primarily triggers losses during the second trimester.
  • Defective Decidualization: Problems with how the endometrial lining responds to pregnancy can extend the "window of implantation," abnormally allowing poor-quality embryos to implant rather than naturally screening them out.

4. Endocrine (Hormonal) Disorders

  • Diabetes: Uncontrolled pre-pregnancy diabetes elevates miscarriage and congenital defect risks.
  • Thyroid Function: Subclinical hypothyroidism and the presence of thyroid peroxidase (TPO) antibodies are loosely linked, though clear causal evidence is still debated.
  • Polycystic Ovary Syndrome (PCOS): Linked to loss through pathways involving hyperandrogenism (elevated androgens), obesity, and insulin resistance, which alters critical implantation proteins like glycodelin.

5. Suspected / Unproven Factors

  • Infections: While historical "TORCH" panels or bacterial vaginosis were routinely blamed, modern evidence does not heavily link them to recurrent losses.
  • Immunological Factors: Despite theories regarding altered maternal immune tolerance (maternal uterine or peripheral natural killer cells rejecting paternal antigens), diagnostic testing remains inconclusive.
  • Male Factor: High sperm DNA fragmentation is increasingly suspected but currently lacks definitive diagnostic consensus.

Prognosis and Management

Despite detailed medical testing, 50% to 70% of recurrent miscarriages remain unexplained. While this can be incredibly frustrating for both patients and clinicians, the general prognosis remains highly encouraging: the vast majority of women with a history of recurrent miscarriages will still successfully achieve a normal live birth over time, with or without medical intervention. Treatment options include anticoagulation therapy (low-molecular-weight heparin/clexane and aspirin) for thrombophilia, surgical corrections for anatomical defects, or IVF paired with pre-implantation genetic testing (PGT) for chromosomal anomalies.