What are the recommendations in British Columbia for a patient with a history of previous preterm labor?

Management of Patients with History of Preterm Labor in British Columbia

For women with a singleton pregnancy and history of prior spontaneous preterm birth between 20 and 36 6/7 weeks of gestation, 17-alpha hydroxyprogesterone caproate (17OHP-C) at 250 mg intramuscularly weekly, starting at 16-20 weeks of gestation until 36 weeks of gestation or delivery, is the recommended treatment.

Evidence-Based Recommendations

For Women with Prior Spontaneous Preterm Birth (SPTB)

• 17OHP-C is the preferred treatment based on strong evidence showing a 34% reduction in recurrent preterm birth (from 54.9% to 36.3%) and significant reductions in infant complications 1
• Treatment should begin at 16-20 weeks gestation and continue weekly until 36 weeks 1
• Vaginal progesterone should not be considered a substitute for 17OHP-C in women with prior SPTB 1

For Women with Short Cervix but No Prior SPTB

• Transvaginal ultrasound cervical length (CL) ≤25 mm is used to diagnose short cervix 1
• For women with CL ≤20 mm before 24 weeks gestation, vaginal progesterone (90-mg gel or 200-mg suppository) is recommended 1
• For women with CL 21-25 mm, vaginal progesterone may be considered based on shared decision-making 1
• 17OHP-C should not be prescribed for treatment of short cervix in women without prior SPTB 1

Management Algorithm

1. For women with prior SPTB:

   • Start 17OHP-C 250 mg IM weekly at 16-20 weeks
   • Continue until 36 weeks gestation
   • Consider cervical length screening

2. If cervical shortening develops while on 17OHP-C:

   • Continue 17OHP-C therapy
   • If cervical length ≤25 mm, consider cervical cerclage 1
   • Do not switch to vaginal progesterone 1

3. For women with no prior SPTB but short cervix:

   • If CL ≤20 mm: Prescribe vaginal progesterone
   • If CL 21-25 mm: Consider vaginal progesterone based on risk-benefit discussion

Important Clinical Considerations

• The mechanism of action for 17OHP-C includes promotion of uterine quiescence, inhibition of pro-inflammatory cells, and immunosuppressive action 2
• Multiple randomized controlled trials have shown that vaginal progesterone is not effective for preventing recurrent preterm birth in women with prior SPTB 1
• The OPPTIMUM study (n=1228) showed no significant difference in PTB <34 weeks between vaginal progesterone and placebo in women with prior SPTB (15.9% vs 18.8%) 1
• Progesterone therapy is not beneficial for multiple gestations, active preterm labor, or preterm premature rupture of membranes 1, 3

Monitoring and Follow-up

• Women with symptoms of preterm labor should be screened for Group B Streptococcus colonization at hospital admission unless screening was performed within the preceding 5 weeks 1
• Women admitted with preterm labor symptoms and unknown GBS status should receive GBS prophylaxis at hospital admission 1
• Regular assessment of cervical length may be beneficial, as approximately 69% of women with prior SPTB maintain cervical length >25 mm 1

Potential Pitfalls

• Delaying initiation of 17OHP-C beyond 20 weeks may reduce effectiveness
• Using vaginal progesterone instead of 17OHP-C for women with prior SPTB is not supported by evidence 1
• Earlier gestational age of previous SPTB is associated with lower response rates to 17OHP-C (odds ratio 0.68; 95% CI 0.56-0.82) 4
• Vaginal bleeding/abruption in the current pregnancy and family history of SPTB are also associated with lower response to 17OHP-C 4

By following these evidence-based recommendations, clinicians can optimize outcomes for women with a history of preterm birth and reduce the risk of recurrence and associated neonatal morbidity and mortality.