PRETERM LABOUR

Definition labour occurring between 20 and 37 weeks gestation complicates about 10% of pregnancies  prematurity is the leading ca...

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