Preterm Labour

Question 1

What period is a “term” delivery over?

Answer 1

• 37-42 weeks

Question 2

How is foetal fibronectin used in labour? What are the main issues with its use?

Answer 2

• Good NPV for labour onset
• Poor PPV. FP with vaginal examination, sex, blood

Question 3

What are the main causes of preterm labour?

Answer 3

• Pre-term labour (spontaneous) - most common
• PROM
• APH
• Hypertension
• Multiple pregnancy
• Infection - collagenases may cause PROM

Question 4

What methods are used to try and predict preterm labour?

Answer 4

• Uterine activity monitoring
• Serial cervical assessment
  
  • Shorter cervical lengths predict risk of preterm labour
• Cervicovaginal microbiology/biochemistry
  
  • Foetal fibronectin - screening test with excellent NPV for preterm delivery but poor PPV

Question 5

What are some risk factors for pre-term labour?

Answer 5

• Maternal - PHx preterm labour, age > 30, uterine abnormalities, cervical trauma or biopsy, uterine abnormalities, systemic disease, vaginal infection (chlamydia, bacterial vaginosis, ureaplasma)
  
  • Short cervical length (<25mm at 25 week scan)
• Foetal - IUGR, PPROM. APH, uterine over-distension
• 50% have no risk factors

Question 6

What are the general prinicples of management if someone presents in preterm labour?

Answer 6

• Admit
• Steroids (IM celestone) if < 34 weeks (readies baby for delivery - causes production of surfactant etc.)
• Tocolytics (stop contractions - NSAIDs like indomethacin or nifedipine, salbutamol) for up to 48 hours (allows admin of steroids and allows for transfer)
• Antibiotics if PPROM or underlying infection, else no evidence
• Monitor closely, deliver if mother/foetus at risk
• Delivery imminent? MgSO4 for neuroprotection (reduces cerebral palsy)
  
  • At < 30 weeks only, as close to 4 hours before birth as possible, within 24 hours of birth

Question 7

What are some contraindications for use of tocolytics in preterm labour?

Answer 7

• Cardiac disease
• Pre-eclampsia
• Hypotension
• Any contraindication to stopping labour
• IUGR
• <20 weeks, >32 weeks

Question 8

How is preterm labour prevented?

Answer 8

• SES
• Control vaginal infection
• Screen and treat asymptomatic bacteruria
• Avoid multiples in ART if possible
• Cervical cerclage (band around the cervix that keeps it long, preventing ascending infection), progesterone (if short cervix)

Question 9

What is the difference between PROM and PPROM? How common are they?

Answer 9

• PROM - rupture >= 37 weeks (i.e. at term)
• PPROM - rupture < 37 weeks (i.e. preterm)
• 10% of pregnancies have one or the other

Question 10

What are the main confirmatory signs/symptoms of PROM?

Answer 10

• Sudden gush of fluid
• Characteristic smell of fluid, alkaline pH
• Uterus may appear small for dates

Question 11

Management of PROM is controversial. What are some options?

Answer 11

• Conservative - requires cephalic, head fixed in pelvis, no intrauterine infection, normal CTG, reliable patient and ability to check pulse and temperature 6-hourly
• Conservative with antibiotics - no evidence, high NNT
• Induced with syntocinon - confirm rupture by pelvic examination
• Induced with prostin as well if unfavourable cervix

Question 12

What are the main features on presentation that might make you suspect that a woman has chorioamnionitis?

Answer 12

• Fever, uterine tenderness, maternal/foetal tachycardia, purulent amniotic fluid
• Generally (but not always) in the setting of PROM