Premature termination of pregnancy Spontaneous abortion. Preterm labor
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ACOG early pregnancy loss preterm labor patient clinical guidance
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https://www.acog.org/womens-health/faqs/preterm-labor-and-bi…
Premature termination of pregnancy
This broadly refers to pregnancy ending before fetal maturity. Main categories include:
| Condition | Usual timing | Core feature |
|---|---|---|
| Spontaneous abortion (miscarriage) | Before fetal viability, commonly defined clinically as before 20 weeks | Spontaneous loss of an intrauterine pregnancy |
| Preterm labor | Before 37 completed weeks | Regular uterine contractions that produce cervical effacement and/or dilatation |
| Preterm birth | Before 37 completed weeks | Delivery after preterm labor or another indicated reason |
Definitions can vary slightly by country and reporting system.
1. Spontaneous abortion
Spontaneous abortion, also called miscarriage, is a non-induced pregnancy loss, most often in the first trimester. Approximately 15% of clinically recognized pregnancies miscarry in the first 3 months. Sporadic fetal chromosomal abnormality, especially aneuploidy, is the most frequent cause. Other contributors include maternal disease, uterine anomalies, infections, and endocrine factors. Textbook of Family Medicine, 9e, p. 493.
Clinical types
| Type | Bleeding/pain | Cervical os | Passage of tissue | Viability |
|---|---|---|---|---|
| Threatened abortion | Mild bleeding, cramps or backache | Closed | No | Pregnancy may be viable |
| Inevitable abortion | Heavy bleeding and cramps, sometimes ruptured membranes | Open or progressing | May not yet have passed | Loss cannot be prevented |
| Incomplete abortion | Heavy bleeding and cramping | Open | Some products retained | Nonviable |
| Complete abortion | Bleeding and pain subside after expulsion | Closed | All products expelled | Nonviable |
| Missed abortion | Often little bleeding or pain | Closed | No | Embryo/fetus has died but is retained |
| Septic abortion | Fever, uterine tenderness, foul discharge, systemic illness | Variable | Variable | Infected pregnancy loss, emergency |
Diagnosis
- Assess hemodynamic stability and amount of vaginal bleeding.
- Confirm pregnancy with urine or serum beta-hCG.
- Perform pelvic examination when appropriate.
- Transvaginal ultrasonography assesses intrauterine pregnancy, viability, and retained tissue.
- In an uncertain early pregnancy, serial beta-hCG and repeat ultrasound may be required.
- Exclude ectopic pregnancy, particularly when there is unilateral pelvic pain, shoulder-tip pain, syncope, hypotension, or no confirmed intrauterine pregnancy.
Management principles
- Threatened miscarriage: expectant care and follow-up when pregnancy is viable; anti-D immunoglobulin is considered for Rh-negative unsensitized patients according to local protocol.
- Incomplete, missed, or early pregnancy loss: expectant, medical, or uterine evacuation options depend on stability, ultrasound findings, gestational age, preference, and infection/bleeding.
- Severe bleeding, shock, suspected ectopic pregnancy, or sepsis: urgent hospital assessment and treatment.
2. Preterm labor
Preterm labor is labor occurring before 37 weeks with uterine contractions that cause cervical change. It is not simply contractions: cervical effacement or dilatation distinguishes true preterm labor from false labor.
Preterm birth is delivery before 37 completed weeks. It may follow spontaneous preterm labor, preterm prelabor rupture of membranes, or be medically indicated for maternal or fetal reasons.
Symptoms and signs
Symptoms can be subtle:
- Regular or frequent uterine tightening or contractions
- Pelvic or lower abdominal pressure
- Persistent dull low-back pain
- Menstrual-like cramps, with or without diarrhea
- Increased vaginal discharge, or watery, bloody, or mucus-containing discharge
- Gush or trickle of fluid suggesting membrane rupture
ACOG advises contacting an obstetric clinician urgently or going to hospital if these symptoms occur before 37 weeks, especially if fluid leakage, bleeding, or regular contractions are present. ACOG preterm labor guidance
Risk factors
- Previous spontaneous preterm birth
- Short cervical length
- Multiple pregnancy
- Prior cervical surgery or uterine anomaly
- Genital tract infection or intra-amniotic infection
- Vaginal bleeding in pregnancy
- Smoking, substance use, poor nutrition, and major psychosocial stressors
- Maternal medical disorders and some fetal complications
A previous preterm birth increases the risk in a later pregnancy by roughly two to three times, according to ACOG patient guidance.
Diagnosis
Assessment may include:
- Monitoring contractions and fetal wellbeing
- Speculum/pelvic examination for cervical dilatation, bleeding, membrane rupture, or infection
- Transvaginal cervical-length measurement
- Fetal fibronectin testing in selected patients
- Ultrasound for fetal growth, gestational age, placental location, and amniotic fluid
- Tests for ruptured membranes or infection when indicated
Management principles
Management depends on gestational age, membrane status, cervical change, infection, maternal status, and fetal condition.
Possible hospital treatments include:
- Antenatal corticosteroids to accelerate fetal lung maturation when early delivery is likely
- Short-term tocolysis in selected cases to allow time for corticosteroids or maternal transfer
- Magnesium sulfate for fetal neuroprotection at very early gestations where indicated
- Antibiotics for specific infections or preterm prelabor rupture of membranes, not routinely for intact membranes without infection
- Delivery when continuing pregnancy is unsafe, such as with severe infection, placental abruption, major fetal compromise, or certain maternal conditions
For prevention, a short cervix identified before 24 weeks may be treated with vaginal progesterone in appropriate patients. Current ACOG guidance does not recommend intramuscular 17-hydroxyprogesterone caproate for recurrent preterm birth prevention because evidence did not show benefit in the broad population previously treated. ACOG updated progestogen guidance
Key distinction
- Spontaneous abortion: pregnancy loss before viability, often in the first trimester.
- Preterm labor: contractions with cervical change before 37 weeks, with pregnancy potentially still ongoing.
- Preterm birth: actual delivery before 37 weeks.
Urgent assessment is needed for heavy bleeding, fainting, severe abdominal pain, fever, foul-smelling vaginal discharge, fluid leakage, reduced fetal movement, or regular contractions before 37 weeks.
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