Preterm Labor: A Comprehensive Guide for Nurses

Preterm labor is defined as the onset of regular uterine contractions resulting in cervical changes before 37 weeks of gestation. It is a leading cause of neonatal morbidity and mortality worldwide, requiring prompt intervention to delay delivery, if possible, and optimize neonatal outcomes. Nurses play a critical role in recognizing the signs, implementing interventions, and supporting patients and their families.

Definition

• Preterm labor: Regular uterine contractions with cervical changes occurring between 20 and 36+6 weeks of gestation.
• Preterm birth: Delivery before 37 weeks of gestation.

Risk Factors

Maternal Factors:

• History of preterm birth or preterm labor.
• Short cervical length (<25 mm).
• Maternal age (<18 or >35 years).
• Chronic conditions (e.g., hypertension, diabetes).

Pregnancy-Related Factors:

• Multiple gestation.
• Polyhydramnios or oligohydramnios.
• Placental abnormalities (e.g., placenta previa, placental abruption).
• Infections (e.g., urinary tract infection, chorioamnionitis).
• Cervical insufficiency.

Lifestyle Factors:

• Smoking or substance abuse.
• Poor nutrition or underweight.
• High stress or low socioeconomic status.

Pathophysiology

Preterm labor occurs due to various mechanisms, including:

• Inflammation/Infection: Cytokine release triggers uterine contractions and cervical changes.
• Uteroplacental Ischemia: Hypoxia stimulates the release of prostaglandins, initiating labor.
• Mechanical Stretching: Overdistension of the uterus (e.g., in multiple gestation or polyhydramnios).
• Hormonal Changes: Imbalance in progesterone and estrogen may lead to uterine activity.

Clinical Presentation

Symptoms:

• Regular uterine contractions (4 or more in 20 minutes or 8 in an hour).
• Pelvic pressure or a sensation of heaviness.
• Lower backache or abdominal cramping.
• Vaginal spotting or bleeding.
• Increased vaginal discharge or rupture of membranes.

Signs:

Mild to Moderate Exacerbation:

• Tachypnea, tachycardia.
• Use of accessory muscles.
• Prolonged expiratory phase.

Severe Exacerbation:

• Cyanosis.
• Inability to speak in full sentences.
• Silent chest (ominous sign of near-complete airway obstruction).
• Altered mental status (indicates respiratory fatigue or hypoxia).

Diagnosis

1. Clinical Assessment:

• History:
  • Onset, duration, and frequency of contractions.
  • Presence of vaginal bleeding or discharge.
• Physical Examination:
  • Assess uterine activity and cervical status.

2. Laboratory Tests:

• Fetal Fibronectin (fFN): Presence in cervical secretions between 22–34 weeks suggests increased risk of preterm birth.
• Infections:
  • Urinalysis and cultures for UTI or chorioamnionitis.
  • Cervical cultures for sexually transmitted infections.
• Complete Blood Count (CBC): Assess for leukocytosis indicating infection.

3. Imaging:

• Transvaginal Ultrasound: Measure cervical length (<25 mm is a risk factor for preterm labor).
• Amniotic Fluid Index (AFI): Evaluate for polyhydramnios or oligohydramnios.

Management of Preterm Labor

Goals:

• Delay delivery to allow for fetal lung maturity.
• Treat underlying causes or contributing factors.
• Optimize maternal and fetal outcomes.

1. Tocolytic Therapy (Delay Labor):

Medications to suppress uterine contractions for up to 48 hours:

• Nifedipine (Calcium Channel Blocker):
  • Reduces uterine contractions by inhibiting calcium influx.
  • Dose: 20 mg orally, then 10–20 mg every 4–6 hours.
• Terbutaline (Beta-Agonist):
  • Relaxes uterine muscles.
  • Use with caution due to potential side effects (e.g., tachycardia).
• Magnesium Sulfate:
  • Neuroprotection for the fetus if delivery is imminent before 32 weeks.
• Indomethacin (NSAID):
  • Inhibits prostaglandin synthesis but is typically used before 32 weeks due to potential adverse effects on the fetal ductus arteriosus.

2. Corticosteroids (Enhance Fetal Lung Maturity):

• Betamethasone or Dexamethasone:
  • Administered to mothers between 24 and 34 weeks of gestation.
  • Betamethasone: 12 mg IM every 24 hours for 2 doses.
  • Reduces the risk of neonatal respiratory distress syndrome, intraventricular hemorrhage, and necrotizing enterocolitis.

3. Antibiotics:

• For preterm premature rupture of membranes (PPROM) or suspected infections.
• Broad-spectrum antibiotics:(e.g., ampicillin and azithromycin) to reduce chorioamnionitis.

4. Hydration and Rest:

• Encourage hydration to reduce uterine irritability.
• Bed rest may be recommended, but prolonged bed rest is no longer standard due to risks of thromboembolism.

5. Cerclage (if indicated):

• Surgical intervention to reinforce the cervix in cases of cervical insufficiency.

Nursing Interventions

1. Assessment and Monitoring:

• Monitor uterine contractions and fetal heart rate.
• Assess cervical changes via vaginal examination or ultrasound.
• Monitor vital signs and signs of infection (e.g., fever, foul-smelling discharge).

2. Administer Medications:

• Provide tocolytics, corticosteroids, and antibiotics as prescribed.
• Monitor for side effects (e.g., tachycardia with terbutaline, hypotension with nifedipine).

3. Education and Emotional Support:

• Educate the patient about preterm labor symptoms and when to seek help.
• Explain the purpose and potential side effects of medications.
• Provide reassurance and involve family members in care.

4. Prevent Complications:

• Maintain strict intake and output records to prevent fluid overload.
• Ensure aseptic technique during cervical examinations to prevent infection.

5. Documentation:

• Record uterine activity, fetal heart rate, medication administration, and patient response.
• Document patient education and emotional support provided.

Complications of Preterm Labor

Maternal:

• Psychological stress and anxiety.
• Side effects of medications (e.g., pulmonary edema, tachycardia).
• Increased risk of cesarean delivery.

Neonatal:

• Respiratory distress syndrome (RDS).
• Intraventricular hemorrhage.
• Necrotizing enterocolitis.
• Long-term neurodevelopmental delays or disabilities.

Prevention of Preterm Labor

Regular Prenatal Care:

• Early detection of risk factors (e.g., short cervix, infections).

Lifestyle Modifications:

• Encourage smoking cessation and proper nutrition.

Progesterone Therapy:

• For women with a history of preterm birth or a short cervix.

Treat Infections Early:

• Prompt treatment of UTIs, bacterial vaginosis, or other infections.

Conclusion

Preterm labor is a significant concern in obstetric care, requiring timely intervention and a multidisciplinary approach to minimize maternal and neonatal risks. Nurses are integral to identifying early signs, managing treatment, and educating patients to improve outcomes. Through vigilant monitoring and evidence-based care, nurses can make a profound difference in the management of preterm labor.