Premature Labour

Prematurity

  • Babies are considered non-viable below 23 weeks.
  • Generally from 23 to 24 weeks, they would not consider resuscitation in babies that do not show signs of life. “23 weekers” have around a 10% chance of survival.
  • From 24 weeks onwards there is a 50% chance of survival, and full resuscitation is offered.

WHO definition of prematurity:

  • Extreme preterm: < 24 weeks
  • Very preterm: 28 – 34 weeks
  • Moderate to late preterm: 32 – 37 weeks
  • Term: > 37 weeks

 

Prophylaxis of Preterm Labour

Vaginal Progesterone

  • This involves giving progesterone vaginally (via gel or pessary).
  • Progesterone has a role in maintaining pregnancy and preventing labour by decreasing activity of the myometrium and preventing the cervix remodelling in preparation for delivery.
  • Offered to women with a cervical length <25mm on vaginal ultrasound between 16 and 24 weeks gestation.

Cervical Cerclage

  • This involves putting a stitch in the cervix to add support and keep it closed.
  • This involves a spinal or general anaesthetic.
  • The stitch can them be removed when the woman goes into labour or reaches term.
  • Offered to women with a cervical length <25mm on vaginal ultrasound between 16 and 24 weeks gestation who have had a previous premature birth or cervical trauma (e.g. colposcopy and cone biopsy).

 

Preterm Prelabour Rupture of Membranes

This is where the amniotic sac ruptures, releasing amniotic fluid in prior to the onset of labour and in a pre-term (<37 weeks gestation) pregnancy.

Diagnosis:

    • Speculum examination reveals pooling of amniotic fluid in the vagina (this is diagnostic and no further tests are required.
    • Insulin-like Growth Factor-Binding Protein-1 (IGFBP-1) can be tested on vaginal fluid if there is doubt. This is a protein present in high concentrations in amniotic fluid.
    • Placental Alpha-Microglobin-1 (PAMG-1) is a similar alternative to IGFBP-1.

Prophylactic Antibiotics

    • Prophylactic antibiotics should be given to prevent them developing chorioamnionitis (NICE recommend erythromycin 250mg four times daily for 10 days).

 

Preterm Labour with Intact Membranes

Diagnosis:

  • Clinical assessment should include speculum examination to assess cervical dilatation.
  • If <30 weeks gestation, clinical assessment along is enough to offer management of preterm labour.
  • If >30 weeks gestation, a transvaginal ultrasound can be used to assess the cervical length. If this is <15mm, then management of preterm labour can be offered.
  • Fetal fibronectin is an alternative test to vaginal ultrasound. It is the “glue” between the chorion and the uterus and is found in the vagina during labour.

Management

  • Fetal monitoring (CTG or intermittent auscultation)
  • Tocolysis
  • Maternal corticosteroids
  • Magnesium Sulfate

 

Tocolysis

  • Medication can be used to stop uterine contractions. This is called tocolysis.
  • Nifedipine is the medication of choice for tocolysis.
  • It is used to delay delivery to buy time for further fetal development, administration of maternal steroids or transfer to a more specialist unit (e.g. with neonatal ICU).

 

Antenatal Steroids

  • Giving the mother corticosteroids helps to develop the fetal lungs and reduce respiratory distress syndrome after delivery.
  • They are used in women with suspected preterm labour of babies less than 36 weeks gestation.
  • An example regime would be betamethasone 12mg IM, 2 doses, 24 hours apart.

 

Magnesium Sulfate

  • Giving the mother IV magnesium sulfate helps protect the fetal brain during premature delivery. It reduces the risk and severity of cerebral palsy.
  • They are used in the 24 hours around delivery of preterm babies of less than 34 weeks gestation.
  • Mothers need close monitoring for magnesium toxicity.
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