Preterm delivery Flashcards
What is the definition of preterm delivery?
occurs between 24-37 weeks gestation
(risk highest <34 weeks)
24 weeks is thought of as a miscarriage, although some babies have survived
• Late miscarriage- between 16-23+6 weeks, overlaps with preterm if the foetus is born alive
What are the complications of preterm delivery?
• Prematurity accounts for 80% of neonatal ICU, 20% of perinatal mortality, up to 50% of cerebral palsy
CLD, blindness, disability
Maternal: Infection is frequently associated with preterm labour
C-section is more commonly used
What are the risk factors for spontaneous preterm labour?
• Previous history • Lower socioeconomic class • Extremes of maternal age • A short interpregnancy interval • Maternal medical disease eg. renal failure, DM or thyroid • Pregnancy complications eg. pre-eclampsia, IUGR • Male foetal gender • High haemoglobin • Sexually transmitted & vaginal infections- eg. BV • Previous cervical surgery • Multiple pregnancy • Uterine abnormalities • Fibroids • Urinary infection • Polyhydramnios • Congenital foetal abnormalities • Antepartum haemorrhage
What are the mechanisms of preterm delivery?
Too many defenders: multiple pregnancy, polyhydraminos
Defenders give up: pre- eclampsia, IUGR or infection, placental abruption will often be followed by labour
Castle design is poor: uterine abnormalities, such as fibroids or congenital (Mullerian duct)
The wall is weak: cervical incompetence, when the cervix painlessly dilates and precedes some preterm deliveries, some cervical surgery (for CIN or CA) or multiple dilations of the cervix
Enemy knock down the walls: BV, GBS, trichomonad, chlamydia
o Chorioamnionitis
o Offensive liquor
o Neonatal sepsis
o Endometritis
Enemy get around the walls: UTI and poor dental hygiene
What is cervical cerclage?
insertion of one or more sutures in the cervix to strengthen it and keep it closed
o Elective at 12-14 weeks
o Cervix can be scanned and only sutured if significant shortening- usual policy
o Rescue suture- prevent delivery even when the cervix is widely dilated in up to 50% of suitable women
What are the prevention techniques for preterm delivery?
Cervical cerclage
Progesterone supplementation
Infection: Screening and treatment of STIs, UTIs and BV (before 16 weeks)
Foetal reduction: offered at 10-14 weeks
Polyhydraminos treatment: needle aspiration (amnioreduction) or NSAIDs (foetal surveillance) (cause (reversible) premature closure of the foetal ductus arteriosus)
Treatment of medical disease: autoimmune and thyroid
What are the clinical features of preterm delivery?
- Women present with painful contractions, but >50% will spontaneously resolve and not result in delivery until term
- Cervical incompetence is painless cervical dilation- women may experience a dull suprapubic ache or increased discharge
- Antepartum haemorrhage and fluid loss
- Fever and severe sepsis may occur
What are the investigations for preterm delivery?
- A negative ‘point of care’ testing (foetal fibronectin assay) means preterm delivery within the next week is unlikely- TVS of cervical length is also predictive with delivery unlikely if >15mm
- CTG and USS are used to assess the foetal state
- Vaginal swabs should be taken- maternal CRP usually rises with chorioamniotitis- WCC is useful, but steroids also cause it to rise
What is the management for preterm delivery?
• Steroids are given between 23-34 weeks in women who are presenting with contractions, can be restricted to those who are fibronectin +ve or have a short cervix
Promote pulmonary prematurity, extra insulin needs to be given to diabetic patients
• Take 24hrs to work, so delivery is artificially delayed using tocolysis
• Tocolysis- nifedipine or oxytocin receptor antagonists (eg. atosiban) can be given to allow steroids time to act or allow in utero transfer to a unit with NICU- it delays rather than stops preterm labour and should not be used for more than 24hrs or in the presence of an infection
Why is magnesium sulphate used in preterm delivery?
neuroprotective for the neonate if given <12hrs prior to anticipated or planned preterm labour
• Single dose of 4g by slow IV infection is used prior to delivery between 23-34 weeks, care is required as it is toxic in overdose
What methods of delivery are used in preterm births?
• Vaginal delivery reduces incidence of neonatal respiratory distress syndrome
most preterm are in breech position, so C-section is common
membranes may not rupture in labour, at least up to 32 weeks, so labour may be slow allowing steroids to act
• Forceps rather than Ventouse are used only for the usual obstetric indications
• Unless immediate neonatal resuscitation is required- the cord should not be clamped for 45 seconds to reduce neonatal morbidity
• Antibiotics for delivery are recommended for women in actual preterm labour because of the increased risk and morbidity of GBS
What are the complications of prelabour rupture of membranes?
• Preterm delivery is the principal complication- follow with 48hrs in >50% of cases
• Infection of foetus, placenta (chorioamnionitis) or cord (funisitis) is common
the earlier the gestation at membrane rupture, the higher the risk of pre-existing infection
• Prolapse of the umbilical cord may occur rarely- absence of liquor can result in pulmonary hypoplasia and postural deformities
What are the clinical features of prelabour rupture of membranes?
- Presents with a gush of clear fluid, followed by further leaking
- A pool of fluid in posterior fornix on examination is diagnostic- digital examination is avoided for fear of infection
- Chorioamniotitis is characterised by contractions or abdominal pain, fever or hypothermia, tachycardia, uterine tenderness and coloured or offensive liquor
What are the investigations for prelabour rupture of membranes?
- ‘Point of care’ tests are available in doubtful cases
- USS may reveal reduced liquor, but the volume can also be normal as foetal urine production continues
- High vaginal swab, FBC and CRP are taken to look for infection, lactate assesses severity of sepsis
- Foetal well-being is assessed by CTG- a persistent foetal tachycardia is suggestive of infection
What is used in the prevention of infection for prelabour rupture of membranes?
- Prophylactic use of erythromycin in women even without clinical evidence of infection is usual
- Co-amoxiclav is contraindicated, as the neonate is more prone to necrotising enterocolitis
