see also:

• labour

• UTI / pyelonephritis
• Abruption
• Cervical incompetence
• Cervical surgical procedures
• Uterine anomalies
• Polyhydramnios
• Smoking
• Illicit drug use
• Multiple gestation
• Abnormal karyotype
• genetic factors:
  • see Nature Genetics. (2023) Genetic effects on the timing of parturition and links to fetal birth weight
  • “the woman's genes favor earlier onset of labor to expel the child, for her own survival, while those of the unborn child favor extension of the pregnancy to gain weight. So, they reach a kind of compromise deal”
  • 15 of the gestational duration genetic variants act through the maternal genome
  • 7 act both through the maternal and fetal genomes
  • 2 act only via the fetal genome

• Ensure that the expected date of delivery is correct by reviewing early ultrasound scans
• Assess for presence of risk factors and associations with preterm labour
• Assess the likelihood of delivery within the next 7 days
• Assess fetal and maternal wellbeing

• check for UTI, bleeding, etc
• MSU m/c/s, FBE, and possibly C reactive protein (CRP)
• assess frequency and regularity of uterine contractions
• abdominal palpation to determine fetal size and presentation, assess for signs of chorioamnionitis, abruption etc.
• if > 25+6 wks, contact midwife to perform CTG
• contact obstetric registrar who may consider VE to:
  • Exclude PPROM
  • Visualise pooling of liquor (note presence of vernix)
  • Collect cervical and vaginal/anal (including GBS) microbiological swabs
  • Perform fetal fibronectin (fFN) testing where indicated (fFN is a screening test used to assess the risk of preterm delivery within the next seven days)
    • indications for fFN testing:
      • symptomatic preterm labour between 24 and 36 weeks gestation and intact membranes and cervical dilatation less than 3 cm
    • contra-indications to fFN testing:
      • Ruptured membranes
      • Visual evidence of moderate or gross bleeding (small amounts of bleeding do not appear to interfere).
      • Cervical cerclage insitu
      • relative C/I include:
        • After the use of lubricants or disinfectants
        • Within 24 hours of coitus
        • Within 24 hours of vaginal examination
        • In the presence of moderate or worse bleeding
        • Recent transvaginal scan
  • If PPROM excluded a digital assessment of cervical dilatation is appropriate (after fFN testing if indicated)
    • If >/= 3cm dilated or short cervix preterm labour likely.
  • consider USS:
    • to assess fetal number, size, presentation, fetal malformations (if morphology unknown), liquor volume and placenta localization, Doppler studies
    • if fFN is positive, consider requesting transvaginal ultrasound of cervical length (TVCL) as an additional screening test that can aid in assessing the risk of preterm delivery.

• differentiating threatened preterm labour from preterm labour can be difficult and will often require repeated assessment (2 -4 hourly) for cervical change over time.
• patients at low risk could be discharged home with review in 7 days, although those who have regular and painful contractions but none of the above features should be observed for 2 or more hours to assess whether or not it is only threatened rather than actual labour.
• higher risk patients require admission or transfer and thus proceed with the following Mx if either:
  • positive fFN
  • evidence of cervical change (+/- TVCL < 15 mm)
  • contractions are persistent and painful
• outcomes for extremely preterm infants depend on place of birth and access to neonatal intensive care.
• Maternal transfer is generally safer for gestations < 32 weeks than neonatal retrieval if delivery is not imminent.

• CTG monitoring until contractions cease
• Pulse rate, respiratory rate and blood pressure monitoring
  • every thirty minutes for first hour, then
  • second hourly for 24 hours, then
  • four hourly
• Measure and record temperature every four hours

• prophylactic antibiotics are not recommended in threatened preterm labour.
• Prophylactic antibiotics for GBS should be administered in established preterm labour irrespective of GBS status.
  • iv benzyl penicillin 1.2g stat then 600mg 4hrly
  • Western Health policy 2013 advises Lincomycin 600 mg IV every 8 hours until delivery for those with penicillin hypersensitivity
• see RCH GBS intrapartum strategies guideline (pdf)

• The aim of tocolysis is to suppress uterine contractions and delay preterm delivery to:
  • allow in-utero transfer to an appropriate level facility, if appropriate,
  • allow for the administration of corticosteroids.
• use immediate release tablets not sustained release tablets
• initial dosing:
  • 20mg orally stat
  • If contractions persist after 30 minutes: Repeat 20 mg
  • If contractions persist after a further 30 minutes: Repeat 20 mg
• maintenance dosing:
  • If blood pressure is stable, 20 mg every 6 hours for 48 hours.
  • Further maintenance therapy is ineffective and is not recommended
  • Maximum dose is 160 mg/day

• Gestation > 34+0 weeks
• Labour is too advanced
• In-utero fetal death
• Lethal fetal anomalies
• Suspected fetal compromise
• Placental abruption
• Suspected intra-uterine infection
• Maternal hypotension: BP < 90 mmHg systolic

• Cautiously give tocolysis if:
  • pre-eclampsia
  • placenta praevia (if not bleeding)

• Nifedipine is the tocolytic of choice ((King et al. 2003).
• Nifedipine is a calcium channel blocker that relaxes smooth muscle.
• It is an effective tocolytic with fewer side effects than other tocolytics available.

• previous adverse reaction to calcium channel blockers
• maternal cardiac disease
• hypotension
• hepatic dysfunction
• concurrent use with salbutamol or other beta-sympathomimetics
• concurrent use of nitrates or antihypertensive medication

• corticosteroids are effective in reducing adverse perinatal outcomes, most notably respiratory distress syndrome, and in increasing the likelihood of neonatal survival (Roberts, Dalziel 2008)
• initial dosing:
  • Administer IM betamethasone in two doses of 11.4 mg (5.7 mg x 2) 24 hours apart to the woman if birth is likely to occur between 23+0 and 35+0 weeks (N.B. The most recent RCOG guideline has increased the recommended threshold to 35+0 weeks). Monitor blood glucose levels, especially in women with diabetes.
• maintenance dosing:
  • repeat doses of corticosteroids in pregnancy, either prophylactically or in the acute setting, should only be undertaken after consultant review. The use of repeat courses of steroids is best limited to gestation less than 32+0 weeks, in which case most women will have been transferred to a tertiary centre.

• Cephalic presentation - Vaginal birth
• Breech presentation – If aggressive neonatal management anticipated then caesarean section may be the safest mode of delivery if time permits. If the baby is at borderline gestation then vaginal birth may be more appropriate.
• Multiple pregnancy – Caesarean section

• Cephalic presentation - vaginal birth
• Breech presentation - caesarean section

• attendance of a paediatrician at the time of birth is essential
• cord blood samples (arterial and venous) should be collected for blood gas analysis
• collect and send placenta for:
  • histopathology (including check for chorioamnionitis)
  • swabbing for microbiological evidence of infection