What is the management plan for a woman at risk of preterm birth?

Management of Women at Risk of Preterm Birth

For women at risk of preterm birth, the management plan should include cervical length screening, vaginal progesterone for short cervix, antenatal corticosteroids for fetal lung maturity if delivery is anticipated before 35 weeks, and avoidance of ineffective interventions such as bed rest and home uterine activity monitoring. 1, 2

Risk Assessment and Screening

Identification of Risk Factors

• Previous spontaneous preterm birth (strongest predictor)
• Short cervical length on ultrasound
• Multiple gestation
• Uterine anomalies
• Cervical procedures (LEEP, cone biopsy)
• Bacterial vaginosis
• Periodontal disease

Cervical Length Screening

• Transvaginal ultrasound is the recommended approach for cervical length measurement 1
• A midtrimester cervical length of ≤25 mm is diagnostic of a short cervix 1
• Measurements should follow standardized procedures as described by organizations such as the Perinatal Quality Foundation or the Fetal Medicine Foundation 1

Interventions Based on Risk Factors

For Short Cervix (Without Prior Preterm Birth)

• Vaginal progesterone is recommended for women with a cervical length ≤20 mm diagnosed before 24 weeks 1
• Consider vaginal progesterone for cervical length 21-25 mm based on shared decision-making 1
• Do not use 17-alpha hydroxyprogesterone caproate for short cervix (including compounded formulations) 1
• Cerclage is not recommended for short cervix (10-25 mm) without cervical dilation in women without a history of preterm birth 1
• Cervical pessary is not recommended for prevention of preterm birth 1

For Women with Prior Preterm Birth

• More intensive interventions may be required during the interconception period 1
• Preconception care to identify and modify maternal risk factors before the next pregnancy 1

For Multiple Gestations

• Routine use of progesterone, pessary, or cerclage is not recommended for cervical shortening in twin gestations 1

Monitoring and Management

Avoid Ineffective Interventions

• Home uterine activity monitoring (HUAM) is not recommended as studies have shown it is not effective in preventing preterm birth 1, 3
• Salivary estriol testing is not recommended due to high false-positive rates and lack of established usefulness 1
• Activity restriction (bed rest) should not be routinely prescribed as evidence suggests it may actually increase the risk of preterm birth 2, 1

Effective Interventions

• Antenatal corticosteroids should be given to improve fetal lung maturity if delivery is anticipated before 35 weeks' gestation 1
• For women with preeclampsia/HELLP syndrome at risk of preterm delivery:
  • Low-dose aspirin (100-150 mg) daily from week 12 to weeks 36-37 for prevention 1
  • Calcium supplementation (≥1 g/day) may reduce risk, particularly for women with low calcium diet 1
  • Antihypertensive treatment to keep SBP <160 mmHg and DBP <110 mmHg 1
  • Magnesium sulfate for seizure prevention and neuroprotection if delivery is required before 32 weeks 1

Medication Management

• For tocolysis in acute preterm labor, options include:
  • Nifedipine (oral calcium channel blocker) 4
  • Beta-mimetics (terbutaline, ritodrine)
  • Magnesium sulfate
  • NSAIDs (indomethacin)

Transfer of Care Considerations

• Women at high risk of imminent preterm birth should be transferred to facilities with appropriate neonatal intensive care capabilities 1
• Delivery should occur in a medical center with an experienced resuscitation team and NICU availability to ensure the best possible neonatal outcomes 5

Common Pitfalls to Avoid

1. Relying on ineffective interventions: Home uterine monitoring, salivary estriol testing, and bed rest lack evidence of effectiveness 1, 5
2. Delaying antenatal corticosteroids: These should be administered promptly when preterm birth is anticipated 1
3. Using 17-alpha hydroxyprogesterone caproate for short cervix: This is not recommended for women without prior preterm birth 1
4. Prescribing activity restriction: This may actually increase risk of preterm birth and has other negative consequences 2, 1
5. Failing to screen for cervical length: This is one of the better available clinical predictors of spontaneous preterm birth 1

By implementing this evidence-based approach to managing women at risk of preterm birth, clinicians can help reduce the incidence of preterm delivery and improve maternal and neonatal outcomes.