Cervical length & Prediction of preterm labor Cervical length & Prediction of preterm labor


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  • Cervical length & Prediction of preterm labor Cervical length & Prediction of preterm labor

    1. 1. Cervical length & Prediction of preterm labor Current Opinion in Obstetrics & Gynecology 19, April 2007 p.191~195 부산백병원 산부인과 R2 정은정
    2. 2. Abstract <ul><li>Purpose of review: summary in clinical use of cervical length for prediction of preterm birth . </li></ul>
    3. 3. Abstract <ul><li>Aymptomatic women c prior cone biopsy, mullerian anomalies, multiple D&C. </li></ul><ul><li>Asymptomatic women once short cervical length </li></ul><ul><ul><li>prior preterm birth </li></ul></ul><ul><ul><li>cervical length < 25 mm. </li></ul></ul><ul><li>Preventing preterm birth  benefit of USG-indicated cerclage(progesterone & indomethacin) </li></ul>
    4. 4. Abstract <ul><li>Symptomatic preterm labor: knowledge of cervical length (fetal fibronectin)  beneficial </li></ul><ul><ul><li>Time to triage </li></ul></ul><ul><ul><li>Reduction of preterm birth </li></ul></ul>
    5. 5. Abstract <ul><li>Transvaginal ultrasound cervical length </li></ul><ul><ul><li>Screening tool for prediction preterm birth </li></ul></ul><ul><ul><li>Prevention of preterm birth  significantly improve health outcomes of pregnant pts & their babies. </li></ul></ul>
    6. 6. Introduction <ul><li>Preterm birth (PTB) : over 12% of births in the USA, over 500000/ yr  incidence is increasing . </li></ul><ul><li>PTB: main cause of perinatal morbidity and mortality  most important in obstetrics </li></ul>
    7. 7. Cervical length by transvaginal ultrasound <ul><li>Best predictive accuracy: CL < 25 mm. </li></ul><ul><li>Different populations (Spontaneous PTB <GA 35 wks) </li></ul><ul><ul><li>asymptomatic low-risk or high-risk women with singleton gestations, </li></ul></ul><ul><ul><li>women with twin,triplet pregnancies </li></ul></ul><ul><ul><li>symptomatic women with preterm labor or preterm premature rupture of membranes (PPROM). </li></ul></ul><ul><ul><li>pts with cerclage in place. </li></ul></ul><ul><li>More relevant studies and recent advances </li></ul>
    8. 8. Cervical length as a screening <ul><li>Specific criteria for screening test </li></ul><ul><li>Cinically important & prevalent condition. </li></ul><ul><ul><li>PTB : main cause of perinatal morbidity & mortality. </li></ul></ul><ul><li>Safe & well accepted. </li></ul><ul><ul><li>safe & no inoculation of bacteria (ex PPROM) </li></ul></ul><ul><ul><li>well accepted by pregnant women. </li></ul></ul><ul><ul><li>Pain and severe discomfort < 2% </li></ul></ul>
    9. 9. Cervical length as a screening <ul><li>Recognize disease in asymptomatic phase. </li></ul><ul><ul><li>Initially, internal os progressively shortens  Cx widens along endocervical canal from internal towards external os.  external os opens. </li></ul></ul><ul><ul><li>earliest changes at internal os :asymptomatic,  only detected by TVU of Cx. </li></ul></ul><ul><li>Well described technique, reliable, reproducible </li></ul>
    10. 10. Cervical length as a screening <ul><li>Have validity </li></ul><ul><ul><li>Digital vs TVU examinations of CL every 2 wks (GA 14 ~GA 30) predict PTB  TVU much stronger </li></ul></ul><ul><ul><ul><li>subjective </li></ul></ul></ul><ul><ul><ul><li>not accurate for evaluating internal os and nonspecific (15 – 16% of primipara 17 – 35% of multipara :1 – 2 cm dilated Cx in late 2 nd trimester) </li></ul></ul></ul><ul><ul><li>Sonographic cervical length :11 mm longer than manual estimations. </li></ul></ul><ul><ul><li> TVU superior to manual exam for evaluation of Cx & prediction of preterm birth. </li></ul></ul>
    11. 11. Cervical length as a screening <ul><li>Intervention prevent outcome. </li></ul><ul><ul><li>Cervical length shortens, cerclage </li></ul></ul><ul><ul><li>Other interventions : indomethacin, progesterone, antibiotics in asymptomatic women & PTL protocol in symptomatic women </li></ul></ul>
    12. 12. Predictive accuracy of CL & prevention of preterm birth in different populations
    13. 13. Low-risk <ul><li>Mean of 35 – 40 mm (GA 14 ~30 wk ) lower 10th percentile: 25 mm. </li></ul><ul><li>Progressive shortening of Cx after 30 wks </li></ul><ul><li>Shorter cervical length  higher risk for PTB. </li></ul><ul><li>Positive predictive value for CL: 15–34 mm  6 ~ 44% [sensitivity low] </li></ul><ul><li>82% short CL at 24 weeks delivered at or after 35 weeks </li></ul><ul><li>USG-indicated cerclage not prevent PTB  not recommend cervical length as a routine screening predictor of PTB in low-risk women. </li></ul>
    14. 14. Table 1
    15. 15. Prior preterm birth <ul><li>CL : good predictor of PTB in women at high risk(prior PTB ). </li></ul><ul><li>Sensitivity 60–80%, positive predictive value: 70% ( CL < 25 mm,GA14~ 18 wks ) </li></ul><ul><li>High-risk pts c nl CL (GA14~ 18 wks ) : 4% risk of preterm. </li></ul><ul><li>Timing of TVU cervical length screening in this population is proposed in Fig. 1. </li></ul>
    16. 16. Timing of TVU cervical length screening prior preterm birth
    17. 17. Prior preterm birth <ul><li>We usually stop cervical length measurements at 28 weeks. </li></ul><ul><li>High-risk women of short cervical length often present with PPROM </li></ul><ul><li>USG-indicated cerclage (detection of short cervical length): 39% ↓ in PTB <35 weeks </li></ul>
    18. 18.   Other high-risk women <ul><li>Women with prior cone biopsy , prior multiple D&Es mullerian anomalies (Table 1). </li></ul><ul><li>Uterine anomalies & short cervix : 13-fold ↑ in spontaneous preterm birth( ex unicornuate ut: highest rate of preterm birth) </li></ul><ul><li>Insufficient data to assess efficacy of cerclage in this population . </li></ul>
    19. 19. Multiple gestations <ul><li>PTB: one of most significant contributors to morbidity & mortality in multiple gestations. </li></ul><ul><li>Shortened cervical length : </li></ul><ul><ul><li>predictive accuracy varies </li></ul></ul><ul><ul><li>low sensitivity </li></ul></ul><ul><ul><li>high positive predictive value for PTB </li></ul></ul><ul><li>Cervical length <2 cm : 100% predictive value for PTB ( before 28 wks ) </li></ul><ul><li>Cervical length <2.5 cm (at 24 weeks) strong predictor of PTB </li></ul>
    20. 20. Multiple gestations <ul><li>CL > 3.5 cm at 18 – 26 wks : 4% delivered prior to 35 wks. </li></ul><ul><li>Triplet gestations :TVU CL -predictive of PTB </li></ul><ul><li>More likley short Cx at 24 wks  difficult to discern </li></ul><ul><ul><li>whether short cervix : inherent to women with multiple gestations </li></ul></ul><ul><ul><li>short cervical length later in 2nd trimester in multiple gestations: <== secondary to rapidly expanding ut putting extra pressure on lower part of Ut (not secondary to insufficient cervix) </li></ul></ul>
    21. 21. Multiple gestations <ul><li>CL < 2.0 cm or > 3.5 cm : prediction of PTB in twin gestations. </li></ul><ul><li>CL: prediction of PTB in multiple gestations  applicability limited </li></ul><ul><li>USG-indicated cerclage: recently 215% increase in PTB in women c asymptomatic short CL & twin gestations  </li></ul>
    22. 22. Post cerclage <ul><li>Evaluation of CL before & after cerclage placement : Cx in length ↑ following cerclage  term delivery incidence ↑ </li></ul><ul><li>Similar predictive accuracy for PTB as CL </li></ul><ul><li>CL <2.5 cm & CL above cerclage of < 1 cm  best predictors of PTB </li></ul>
    23. 23. Post cerclage <ul><li>Similar to other populations, shortening of CL benefit following cerclage  no proven intervention </li></ul><ul><li>For patients post history-indicated cerclage, if CL following procedure < 25 mm, placing a re-enforcing cerclage  worse prognosis , should not be done. </li></ul><ul><li>Not recommend routine repeated CL measurement following ultrasound-indicated or physical exam-indicated cerclages ( no intervention studied to affect outcome) </li></ul>
    24. 24. Funneling <ul><li><25% funneling :not associated risk for PTB ↑ </li></ul><ul><li>> 25% funneling : risk for PTB ↑ </li></ul><ul><li>CL : preferred method to screen Cx for risk of PTB, </li></ul><ul><li>Funneling & short cervical length : much worse predictor of PTB than short cervical length alone </li></ul><ul><li>Funneling in normal length Cx (>=25 mm) increases risk for PTB (?)  unclear </li></ul>
    25. 25. Other interventions-Indomethacin <ul><li>Most asymptomatic women c short CL: painless Ut contractions </li></ul><ul><li>Indomethacin : effective at preventing PTB at 48 h, 7 days, less than 37 wks with PTL. </li></ul><ul><li>Asymptomatic women c short CL < 25 mm on TVU at 16 – 24 weeks  Indomethacin </li></ul><ul><ul><li>31% decrease in PTB before 35 wks </li></ul></ul><ul><ul><li>86% decrease in PTB before 24 wks   </li></ul></ul>
    26. 26. Other interventions- Progesterone <ul><li>Effective in reducing incidence of PTB in women c prior PTB 1/3. </li></ul><ul><li>Using 17 hydroxy-progesterone caproate in women with short CL on TVU.  possible decrease in PTB (Unpublished data ,Nicolaides & colleagues, 2006, International Society of Ultrasound in Obstetrics and Gynecology (ISUOG)) </li></ul><ul><li>Insufficient data to assess efficacy of this intervention </li></ul>
    27. 27. Antibiotics <ul><li>Antibiotics for preventing PTB  not very successful in prolongation of pregnance (except PPROM) </li></ul><ul><li>Most recently, antibiotics for asymptomatic women c short CL : not efficacious in improving outcomes   </li></ul>
    28. 28. Preterm labor <ul><li>Symptomatic women with PTL at high risk for PTB, but most of them deliver at term even without interventions. </li></ul><ul><li>Compared with women in whom cervical length and fetal fibronectin (FFN) results  similar women with CL and FFN available for management decisions were triaged about half an hour earlier& less incidence of PTB </li></ul>
    29. 29. Conclusion <ul><li>Cervical length by TVU best available technique for predicting PTB. </li></ul><ul><li>Safe, well accepted, reliable, valid in all populations studied. </li></ul><ul><li>Cervical length of less than 25 mm ( 16 ~ 24 weeks) : most reliable threshold for increased risk of PTB. </li></ul><ul><li>Shorter cervical length  higher risk of PTB. </li></ul>
    30. 30. Conclusion <ul><li>Earlier in GA shortening occurs  higher risk. </li></ul><ul><li>Screening frequency: severity of obstetrical Hx, especially in high-risk populations. </li></ul><ul><li>Prevention strategies,once short cervical length is detected  benefit from ultrasound-indicated cerclage. </li></ul><ul><li>Prior preterm birth or 2nd trimester loss  TVU cervical length < 25 mm at 16 – 23 wks with singleton gestation </li></ul>
    31. 31. Conclusion <ul><li>Other interventions based on short cervical length  indomethacin & progesterone. </li></ul><ul><li>Recent trial ( use of cervical length & FFN) t hreatened PTL : shorter time to triage & decreased incidence of PTB. </li></ul><ul><li>Cervical length significant role in prediction of PTB  Prevention of this common & severe complication </li></ul><ul><li>Screening tool : potential to significantly improve health outcomes of pregnant pts & babies </li></ul>