What is the risk of preterm birth in a patient with a history of Loop Electrosurgical Excision Procedure (LEEP) or cold knife cone biopsy?

Risk of Preterm Birth After LEEP or Cold Knife Cone Procedures

Women who have undergone LEEP or cold knife conization have a significantly increased risk of preterm birth in subsequent pregnancies, with cold knife conization carrying a higher risk than LEEP.

Risk Assessment by Procedure Type

• Cold knife conization (CKC) is associated with approximately 2.5 times higher risk of preterm delivery compared to women without treatment (38.9% vs 20.5%) 1
• LEEP procedures show a more moderate but still significant increased risk (RR 1.58,95% CI 1.37 to 1.81) of preterm birth compared to untreated women 2
• Both procedures lead to shorter cervical length during pregnancy, which is a predictor of preterm birth 3

Risk Factors That Increase Preterm Birth Risk

• Cone depth is a critical factor - risk increases significantly with deeper excisions:
  • Less than 10-12mm depth: 1.5 times increased risk 2
  • More than 15-17mm depth: 2.8 times increased risk 2
  • 20mm or more: 4.9 times increased risk 2
• Repeat cervical procedures multiply the risk (RR 3.78,95% CI 2.65 to 5.39) 2
• Women with positive margins requiring additional procedures face higher risk 4

Specific Preterm Birth Outcomes

• Overall preterm birth (<37 weeks): 11.2% in women with excisional procedures vs 5.5% in untreated women 2
• Severe prematurity (<32-34 weeks): 3.5% vs 1.4% (RR 2.25) 2
• Extreme prematurity (<28-30 weeks): 1.0% vs 0.3% (RR 2.23) 2
• Preterm premature rupture of membranes (pPROM): 6.1% vs 3.4% (RR 2.36) 2

Other Associated Adverse Outcomes

• Low birth weight: 7.9% vs 3.7% (RR 1.81) 2
• NICU admission rates: 12.6% vs 8.9% (RR 1.45) 2
• Perinatal mortality: 0.9% vs 0.7% (RR 1.51) 2
• Shorter average gestational age at delivery, particularly after CKC 1

Monitoring and Prevention Strategies

• Transvaginal ultrasound cervical length screening is recommended between 16-24 weeks 5
  • Cervical length <25mm has good predictive value for preterm birth in women with prior cone biopsy (sensitivity 64%, specificity 78%) 5
  • Negative predictive value of 95.2% when cervical length >3.0cm 3
• Cervical cerclage may be indicated for women with short cervix:
  • Monofilament suture material appears superior to braided suture (15% vs 40% preterm birth rate) 6
• Serial cervical length measurements can help identify women at lower risk:
  • Women with <10% reduction in cervical length between screenings can be considered low risk 6

Clinical Implications

• Women with history of LEEP or CKC should be counseled about increased preterm birth risk before conception 2
• Consider these procedures carefully in women who desire future fertility 1
• When treatment is necessary, LEEP is preferable to CKC for women planning future pregnancies 1
• Minimize cone depth when oncologically appropriate 2
• Avoid repeat procedures when possible 2