Early pregnancy failure (also called early pregnancy loss or miscarriage, usually before 12 weeks) can occur due to a variety of factors. In many cases, the exact cause isn’t identified, but the most common reasons are well understood.
1. Chromosomal abnormalities (most common cause)
Responsible for 50–70% of early miscarriages
The embryo has missing, extra, or abnormal chromosomes
Examples:
Trisomy (extra chromosome)
Monosomy (missing chromosome)
These abnormalities usually happen by chance during fertilization and are not typically inherited
2. Hormonal (endocrine) problems
Low progesterone levels → affects implantation and maintenance of pregnancy
Thyroid disorders (hypothyroidism or hyperthyroidism)
Uncontrolled diabetes mellitus
Polycystic ovary syndrome (PCOS)
3. Uterine and structural abnormalities
Congenital uterine anomalies (e.g., septate uterus)
Fibroids (especially submucosal)
Intrauterine adhesions (Asherman syndrome)
Cervical incompetence (more relevant in later losses)
4. Infections
Certain infections can interfere with early pregnancy:
TORCH infections (e.g., toxoplasmosis, rubella)
Listeria
Syphilis
Severe systemic infections with high fever
5. Immunological factors
Antiphospholipid antibody syndrome (APS)
Autoimmune disorders like lupus
These can cause clotting problems in placental vessels
6. Environmental and lifestyle factors
Smoking
Alcohol consumption
Drug abuse (e.g., cocaine)
Excess caffeine intake
Exposure to radiation or toxic chemicals
7. Maternal age
Risk increases significantly after age 35
Due to higher likelihood of chromosomal abnormalities
8. Chronic maternal illnesses
Severe anemia
Kidney disease
Heart disease
Uncontrolled hypertension
9. Trauma or physical factors
Severe injury or accidents
Extreme stress (rarely a sole cause but may contribute)
Important point
Many early pregnancy failures are natural protective mechanisms, where a non-viable embryo does not continue to develop.
