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Abortion (Obstetrics)

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Classification

By Etiology

By Clinical Presentation (Spontaneous Abortion)

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Epidemiology

• Spontaneous abortion occurs in 10–15% of clinically recognized pregnancies; estimates rise to ~30% when biochemical pregnancies are included.
• The majority (>80%) occur in the first trimester.
• Risk increases sharply with advancing maternal age (>35 years).

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Etiology

First Trimester Spontaneous Abortion

1. Chromosomal abnormalities — most common cause (~50–60%); trisomies (especially 16, 18, 21), monosomy X (Turner), triploidy
2. Structural uterine anomalies — septate uterus, fibroids (submucosal), Asherman syndrome
3. Endocrine factors — uncontrolled diabetes, thyroid dysfunction, luteal phase defect, hyperprolactinemia
4. Antiphospholipid syndrome (APS) — recurrent pregnancy loss with thrombophilia
5. Infections — TORCH (Toxoplasma, Rubella, CMV, HSV), Listeria, Mycoplasma, Chlamydia
6. Immunological — alloimmune factors, NK cell dysfunction
7. Environmental/toxic — smoking, alcohol, radiation, heavy metals
8. Thrombophilias — Factor V Leiden, prothrombin gene mutation, protein C/S deficiency
9. Unexplained — significant proportion remain without identifiable cause

Second Trimester (Late) Abortion

• Cervical incompetence (insufficiency)
• Uterine anomalies
• PPROM
• Antiphospholipid syndrome

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Clinical Features

Threatened Abortion

• Vaginal bleeding in early pregnancy (any amount)
• Cervical os closed
• Uterine size consistent with dates
• Cramping may or may not be present

Inevitable Abortion

• Profuse bleeding + cramping
• Cervical os open
• Membranes may be bulging or ruptured

Incomplete Abortion

• Partial expulsion of products of conception (POC)
• Open os with ongoing bleeding
• Endometrial thickness >15 mm on ultrasound often indicates retained POC

Missed Abortion

• Asymptomatic; diagnosed on ultrasound
• Crown-rump length (CRL) ≥7 mm with no fetal cardiac activity
• Mean sac diameter ≥25 mm with no embryo

Septic Abortion

• Fever, uterine tenderness, purulent discharge
• May progress to septicemia, endotoxic shock, DIC, renal failure
• Causative organisms: Staphylococcus aureus, E. coli, Clostridium perfringens, anaerobes

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Diagnosis

History

• LMP, gestational age, bleeding amount, passage of tissue, associated pain
• Previous obstetric history, APS, structural abnormalities

Examination

• Speculum: os open/closed, tissue at os, bleeding
• Bimanual: uterine size, tenderness, cervical motion tenderness

Investigations

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Management

Threatened Abortion

• Supportive: pelvic rest, avoid intercourse
• No proven intervention to prevent loss if chromosomally abnormal
• Progesterone supplementation (vaginal micronized) may benefit in women with prior miscarriage and subchorionic hematoma
• Serial β-hCG and ultrasound

Inevitable / Incomplete Abortion

1. Expectant management — allow natural expulsion; takes days to weeks; suitable if hemodynamically stable
2. Medical management — Misoprostol (800 mcg vaginal/sublingual); highly effective for first-trimester incomplete/inevitable abortion; success 80–90%
3. Surgical management — Manual vacuum aspiration (MVA) or suction curettage (EVA); sharp curettage now less preferred due to Asherman syndrome risk

Missed Abortion

• All three options (expectant, medical, surgical) are acceptable
• Medical: Mifepristone 200 mg PO → Misoprostol 800 mcg 24–48h later (combination more effective)
• Surgical: MVA or EVA under local/general anesthesia

Complete Abortion

• Confirm by ultrasound (endometrial thickness <15 mm, closed os)
• Expectant; no further intervention usually needed

Septic Abortion

• Emergency — IV broad-spectrum antibiotics (e.g., ampicillin + gentamicin + metronidazole)
• Prompt uterine evacuation (surgical) after antibiotic initiation
• ICU-level care if septic shock, DIC, or multiorgan dysfunction
• Rule out clostridial infection (gas in uterine wall on imaging)

Rh Isoimmunization Prevention

• All Rh-negative unsensitized women with spontaneous or induced abortion should receive anti-D immunoglobulin (50 mcg if <12 weeks; 300 mcg if ≥12 weeks)

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Recurrent Pregnancy Loss (RPL)

Investigation

Management of RPL

• APS confirmed: Low-dose aspirin + LMWH throughout pregnancy
• Inherited thrombophilia: LMWH if loss history is severe
• Uterine septum: Hysteroscopic metroplasty
• Unexplained RPL: Supportive care in dedicated early pregnancy unit improves outcomes; empirical progesterone (PROMISE trial: equivocal; PRISM trial: modest benefit in women with prior loss + bleeding)

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Complications

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Key Points Summary

• Most common cause of first-trimester spontaneous abortion: chromosomal abnormality (~50–60%)
• Diagnostic gold standard: Transvaginal ultrasound
• Medical management: Misoprostol ± Mifepristone
• Surgical management: MVA preferred over sharp curettage
• Septic abortion: Antibiotics first, then urgent evacuation
• Anti-D prophylaxis: Mandatory in all Rh-negative women
• RPL workup: APS, thrombophilia, uterine anatomy, parental karyotype