Cervical insufficiency is clinical diagnosis: Inability of cervix to retain pregnancy in absence of contractions or labor

Short cervix is sonographic observation: Cervical length (CL) < 25 mm at < 24 weeks

Funneling : Protrusion of amniotic membranes into cervical canal

Check CL at beginning of exam as cervix is dynamic

Length is shortest in patients who have recently been upright

Transvaginal US essential in high-risk patients or if CL < 30 mm on transabdominal ultrasound

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  Observe for 3-5 minutes

  
  
  
  
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    Magnify image so cervix occupies 75% of screen

    
    
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    Avoid excessive vaginal transducer pressure

    
    
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    Measure from internal os to external os

    
    
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    Use fundal pressure to unveil short cervix

    
    
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    Look for amniotic fluid “sludge” (layering, inflammatory debris)

  
  

Report single best, shortest cervical length; do not average measurements

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  Worse prognosis if short cervix + funneling

  
  
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  Funneling > 50% of CL is most significant (79% risk preterm birth)

Cerclage monitoring is controversial

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  American College of Obstetrics and Gynecology bulletin says it is not required

  
  
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  Proponents argue that it helps counsel patients regarding prognosis if signs of stitch failure

  
  
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  If scan performed for cerclage follow-up

  
  
  
  
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    Measure functional CL (length of closed cervix regardless of sutures)

    
    
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    Document funneling to or beyond suture

    
    
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    Document presence of amniotic fluid sludge