Pre-term Delivery Flashcards
When does preterm delivery occur?
Under 28 weeks: extreme preterm
28 – 32 weeks: very preterm
32 – 37 weeks: moderate to late preterm
When is neonatal risk highest?
34 weeks
<24 weeks thought of as a miscarriage, although some babies have survived
What % deliveries are preterm?
5-8%
6% present with contractions preterm but deliver at term
What are the causes of preterm delivery?
Spontaneous
Iatrogenic e.g. induced due to foetal or maternal risk
When does late miscarriage occur?
between 16-23+6 weeks
overlaps with preterm if the foetus is born alive
What are the neonatal complications of preterm delivery?
80% neonatal ICU
20% perinatal mortality
50% cerebral palsy
Other long term morbidity:
chronic lung disease
blindness
minor disability
1/3 babies handicapped and 1/3 will die
by 32 weeks, these risks are <5%
Between 34-37 weeks there is increased respiratory distress, infant mortality and an increased risk of subtle cognitive and behavioural problems
What are the maternal complications of preterm delivery?
Infection - frequently associated with preterm labour
Can occasionally cause severe maternal illness and death
C-section is more commonly used
What are the risk factors for spontaneous preterm labour?
previous hx lower SE class Extremes of maternal age short inter pregnancy interval maternal medical disease e.g. renal failure, DM or thyroid pregnancy complications e.g. pre-eclampsia, IUGR male foetal gender high haemoglobin sexually transmitted and vaginal infections previous cervical surgery multiple pregnancy uterine abnormalities fibroids urinary infection polyhydramnios congenital foetal abnormalities antepartum haemorrhage
ANALOGY:
the uterus is a castle, the cervix is the castle wall holding the ‘defenders’ in..
How does the wall get breached!?!
mechanisms affect the defenders, the castle wall or the enemy!!
- TOO MANY DEFENDERS - e.g. twins
- THE DEFENDERS ‘GIVE UP’ -. fetal survival response
- THE CASTLE DESIGN IS POOR - e.g. uterine abnormalities
- THE WALL IS WEAK - cervical incompetence
- THE ENEMY KNOCK DOWN THE WALL! infections
- THE ENEMY GET AROUND THE WALL UTI/dental hygeine are risk factors
you’re crazy
‘too many defenders’ - what does this mean and how does it cause preterm delivery
Multiple pregnancy - increasing contributor, assisted conception
delivery before 34 weeks occurs in 20% twins and is the mean time for twins
Polyhydramnios has the same effect, probably largely mediated by increased stretch
‘the defenders give up’ - meaning?
how does it cause preterm delivery?
foetal survival response - more common where the foetus is at risk
e.g. pre-eclampsia, IUGR or infection
placental abruption will often be followed by labour - iatrogenic preterm delivery attempts to improve upon this mechanism
‘the castle design is poor’ - meaning and how does it cause preterm delivery?
uterine abnormalities, such as fibroids or congenital (Mullerian duct abnormalities)
‘the wall is weak’ - meaning and how does it cause preterm deliveries?
cervical incompetence, when the cervix painlessness dilates and precedes some preterm deliveries
some cervical surgery (for CIN or CA) or multiple dilations of the cervix may be a cause
‘the enemy knock down the walls’ what does this mean and how does is cause pre-term delivery?
infection is implicated in 60% of preterm deliveries and is often subclinical
BV is a known risk factor, but GBC, Trichomonas, Chlamydia and commensals have been implicated
What are the manifestations of infections causing preterm delivery?
Chorioamnionitis
Offensive liquor
Neonatal sepsis
Endometritis
‘the enemy get round the wall’ meaning and how does this cause preterm delivery?
UTI and poor dental hygiene are risk factors
How can preterm labour be predicted?
Cervical length on transvaginal sonography - sensitive and specific indication of preterm labour risk
<25mm cervix - prophylaxis
Prevention strategies (begin at 12 weeks) are limited to women at high risk - most frequently women who have had previous delivery between 16-34 weeks.
What is cervical cerclage?
Cervical cerclage involves putting a stitch in the cervix to add support and keep it closed. This involves a spinal or general anaesthetic. The stitch is removed when the woman goes into labour or reaches term.
Cervical cerclage is offered to women with a cervical length less than 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).
In what situations is cerclage used in?
- Elective at 12-14 weeks
Cervix can be scanned and only sutured if significant shortening - “Rescue” cervical cerclage may also be offered between 16 and 27 + 6 weeks when there is cervical dilatation without rupture of membranes, to prevent progression and premature delivery.
