Preterm labor

Disease Description (Causes and Symptoms)

• Definition: A condition with a risk of preterm birth in which regular uterine contractions are accompanied by cervical effacement (decreased length) or dilation at ≥20 weeks and <37 weeks of pregnancy.
• Main causes and pathophysiology: It is multifactorial rather than caused by a single factor. Common mechanisms include cervical weakness (cervical insufficiency), infection of the uterus or amniotic membranes/placenta (inflammatory response), overdistension due to excessive uterine size or amniotic fluid, placental abruption (bleeding/hematoma), prenatal trauma or surgery, maternal chronic diseases (such as hypertension, kidney disease, and diabetes), and previous preterm birth, multiple gestation, and social or behavioral factors (smoking, drugs, poor nutrition, and stress). Inflammation (especially ascending infection) induces premature aging, extracellular matrix degradation, and increased prostaglandins, triggering contractions and cervical changes.
• Main symptoms: Regular uterine contractions (with decreasing intervals), lower abdominal or pelvic pressure or pain, lower back pain, increased vaginal discharge or bloody discharge, rupture of the amniotic membranes (passage of clear fluid), and a sensation of fetal descent. Clinically, cervical shortening (on ultrasound), confirmation of amniotic fluid leakage by speculum examination, and fetal fibronectin (fFN) testing may be used as diagnostic aids.
• Emergency signs (immediate medical attention required): Regular contractions occurring 4 or more times in 10 minutes (or 6 or more times in 1 hour), leakage of amniotic fluid, persistent vaginal bleeding, decreased fetal movement, or fever (suspected infection).

Treatment Methods

• Overview: The goals are to promote fetal lung maturation, delay acute delivery (for at least 48 hours if possible to allow transfer, steroid administration, and preparation for neonatal care), and treat the cause (such as infection).
• Medication treatment
  • Corticosteroids: Betamethasone or dexamethasone is administered to promote fetal lung maturation (generally recommended between 24 and 34 weeks; guidelines vary by institution).
  • Tocolytics (uterine contraction suppressants): Used depending on the clinical situation. Representative medications include nifedipine (a calcium channel blocker), atosiban (an oxytocin receptor antagonist), beta-adrenergic agonists (used locally and restricted in some countries), and indomethacin (an NSAID, used selectively for a short period in early to mid-pregnancy). These medications have different efficacy and adverse-effect profiles, and contraindications must be assessed (e.g., intrauterine infection, poor fetal condition, placental abruption, or irreversible progression of labor).
  • Magnesium sulfate: Administered mainly for neuroprotection (to reduce the risk of cerebral palsy) before 24–32 weeks; its use as a tocolytic is limited.
  • Antibiotics: Used for preterm premature rupture of membranes (PPROM) or suspected infection (based on clinical findings or test results). Antibiotics may be considered for GBS (group B streptococcus) prophylaxis.
• Mechanical and procedural treatments
  • Cervical cerclage: Preventive or emergency cerclage may be considered in patients diagnosed with cervical insufficiency. It is generally not performed during acute preterm labor (contraindicated in the presence of infection or progressing labor).
• Additional management
  • Fetal and maternal monitoring (fetal heart rate, frequency of uterine contractions, vital signs, and signs of infection).
  • Hospital observation when necessary (for labor control, medication administration, steroid administration, and fetal monitoring).
  • Transfer to a specialist facility: If preterm birth is expected, transfer to a facility capable of neonatal intensive care should be considered (especially before 32 weeks).
• Contraindications/precautions
  • Contraindications to tocolysis: Intrauterine infection (chorioamnionitis), fetal death or lethal anomaly, the need for immediate delivery of the mother or fetus (e.g., serious maternal disease or placental abruption), and an inherent risk of bleeding.
  • Monitor medication adverse effects (e.g., nifedipine → hypotension and headache, magnesium → respiratory depression and decreased reflexes, beta-agonists → palpitations and hypokalemia).

Checkpoints Before an Outpatient Visit (Including Example Questions)

• Items to prepare
  • List of currently used medications and supplements (including dosage and administration times)
  • Gestational age (estimated due date) and previous delivery history (including a history of preterm birth)
  • Recent symptom record (contraction timing, intervals, and intensity; characteristics and amount of vaginal discharge; presence or absence of bleeding; changes in fetal movement)
  • Recent test results (such as ultrasound, blood tests, and urine tests) or medical records
• Main items healthcare providers will check during an outpatient visit
  • Vital signs (blood pressure, temperature, and heart rate)
  • Frequency and regularity of uterine contractions (monitoring or a chart recorded by the patient)
  • Whether the amniotic membranes have ruptured (special tests or speculum examination)
  • Color and odor of vaginal discharge (whether infection is suspected)
  • Cervical length measurement by ultrasound (a cervical length <25 mm is associated with increased risk)
  • Fetal heart rate and activity
  • Consideration of an fFN (fetal fibronectin) test (helps assess the possibility of delivery within 48 hours; when negative, it has a high negative predictive value)
• Example questions before an outpatient visit (items for the patient to ask the healthcare provider)
  • "Do I need to be admitted immediately based on my current symptoms?"
  • "What is the significance of the cervical length measured by ultrasound?"
  • "What additional tests should I undergo?"

Examples of General Questions to Ask the Doctor

• "What treatment will you provide to delay delivery as much as possible in this condition? What are the expected benefits and adverse effects?"
• "Do I need steroids to promote fetal lung maturation? When should they be administered?"
• "What are the criteria for requiring inpatient treatment, and how should I manage this at home?"
• "Are preventive measures (progesterone, support, etc.) needed to prevent recurrence in this pregnancy?"

Examples of Condition-Specific Questions

• "The cervical length on ultrasound is XX mm. Is this value dangerous at my current gestational age? Do I need immediate treatment?"
• "If my membranes have ruptured (watery discharge), which antibiotics and treatments are recommended, and is hospitalization required?"