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PRETERM LABOUR

PRETERM LABOUR
Definition

  1. labour occurring between 20 and 37 weeks gestation
  2. complicates about 10% of pregnancies 
  3. prematurity is the leading cause of perinatal morbidity and mortality
  4. at 30 weeks or 1500 g = 90% survival
  5. at 33 weeks or 2000 g = 99% survival
  6. major causes of morbidity = asphyxia, sepsis, RDS
  7. intrapartum asphyxia may lead to cerebral hemorrhage
Etiology

idiopathic (most common)

Maternal
  1. preeclampsia/hypertension
  2. placenta previa or abruption
  3. uncontrolled diabetes
  4. recurrent pyelonephritis and untreated bacteriuria
  5. maternal genital tract infection
  6. chorioamnionitis
  7. other medical illness (heart disease, renal disease, severe anemia, systemic infection, chronic vascular disease)
  8. maternal age < 18 years or > 40 years
  9. fibroids or other uterine anomalies
  10. incompetent cervix
  11. history of abortions or stillbirths
  12. surgical (intra-abdominal surgery, cholecystitis, peritonitis)
  13. previous incision into uterus or cervix (C/S, conization)
  14. low socioeconomic class
  15. lack of prenatal care
  16. poor nutrition
  17. low prepregnancy weight
  18. smoking
  19. drug addiction (alcohol, cocaine)
  20. stress/anxiety/fatigue
  21. prior history of premature delivery (recurrence risk of 17-40%)

Maternal-fetal
  1. PPROM (a common cause)
  2. polyhydramnios

Fetal
  1. multiple gestation
  2. congenital abnormalities of fetus

Requirements for Consideration of Labour Suppression(Tocolysis) 

  1. live fetus 
  2. fetal immaturity 
  3. intact membranes 
  4. cervical dilatation of 4 cm or less 
  5. absence of maternal or fetal contraindications (see below) 
  6. availability of necessary personnel and equipment to assess mother and fetus during labour and care for baby of the predicted GA if  therapy fails

Maternal Contraindications to Tocolysis 

  1. bleeding (placenta previa or abruption) 
  2. maternal disease (hypertension, diabetes, heart disease)
  3. preeclampsia or eclampsia
  4. chorioamnionitis
Fetal Contraindications to Tocolysis 

  1. erythroblastosis fetalis 
  2. severe congenital anomalies 
  3. fetal distress/demise IUGR,
  4. multiple gestation (relative)

Diagnosis

  1. regular contractions (2 in 10 minutes)
  2. cervix > 2 cm dilated or 80% effaced OR documented change in cervix
Prevention

  1. good prenatal care
  2. identify pregnancies at risk
  3. treat silent vaginal infection or UTI
  4. patient education
  5. the following may help but evidence for their effectiveness is lacking
  6. rest, time off work, stress reduction
  7. improved nutrition
  8. U/S measurement of cervical length or frequent vaginal exams to assess cervix; this would catch PTL earlier so tocolysis would be more effective
Management

Initial
  1. transfer to appropriate facility
  2. hydration (NS @ 150 mL/hour)
  3. bed rest in left lateral decubitus position
  4. sedation (morphine)
  5. avoid repeated pelvic exams (increased infection risk)
  6. U/S examination of fetus (for GA, BPP, position)
  7. prophylactic antibiotics; controversial but may help delay delivery
aggressiveness depends on the GA

Tocolytic agents - if no contraindications present

  1. have no impact on neonatal morbidity or mortality but may buy time to allow celestone use or to transfer to appropriate centre
  2. beta-mimetics: ritodrine, terbutaline
  3. magnesium sulphate (if diabetes or cardiovascular disease present)
  4. calcium channel blockers: nifedipine
  5. PG synthesis inhibitors (2nd line agent): indomethacin

Enhancement of Pulmonary Maturity

  1. most effective between 28 and 34 weeks gestation
  2. treatment: betamethasone valerate  12 mg IM q12h times 2
  3. wait 24 hours for delivery
  4. specific maternal contraindications
    • active TB
    • viral keratosis
    • maternal DM
PRETERM LABOUR PRETERM LABOUR Reviewed by Radiology Madeeasy on December 25, 2010 Rating: 5
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