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.
How is progesterone used to prevent preterm delivery?
Progesterone can be given vaginally via gel or pessary as prophylaxis for preterm labour. 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. This is offered to women with a cervical length less than 25mm on vaginal ultrasound between 16 and 24 weeks gestation.
How is infection leading to preterm delivery prevented?
Screening and treatment of STIs, UTIs and BV (before 16 weeks) is beneficial
What is done WRT foetal reduction?
reduction of higher order multiples is offered at 10-14 weeks
How is polyhydramnios treated to prevent preterm delivery?
Needle aspiration (amnioreduction or NSAIDS (foetal surveillance) - reduce foetal urine output, but can occasionally cause (reversible) premature closure of the foetal ductus arteriosus
What medical diseases can cause preterm delivery?
placental disease associated with autoimmune disease
thyroid antibodies - thyroxine
What are the clinical presentations of preterm delivery?
Painful contractions - but >50% will spontaneously resolve and not result in delivery until term
antepartum haemorrhage and fluid loss
fever and sepsis
How does cervical incompetence present?
painless cervical dilation
women may experience a dull suprapubic ache or increased discharge
What does fluid loss suggest?
Ruptured membranes
What confirms diagnosis of preterm delivery when fever and sepsis have occurred?
Vaginal exam - dilated cervix confirms diagnosis
Vaginal swabs should be taken
What does a negative ‘point of care’ testing indicate?
Preterm delivery within the next week is unlikely
How is foetal state assessed in preterm delivery?
CTG and USS
How is preterm delivery managed?
Fetal monitoring (CTG or intermittent auscultation)
Tocolysis with nifedipine: nifedipine is a calcium channel blocker that suppresses labour
Maternal corticosteroids: can be offered before 35 weeks gestation to reduce neonatal morbidity and mortality
IV magnesium sulphate: can be given before 34 weeks gestation and helps protect the baby’s brain
Delayed cord clamping or cord milking: can increase the circulating blood volume and haemoglobin in the baby at birth
Which women are given 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 two doses of intramuscular betamethasone, 24 hours apart.
Why are steroids given in preterm contractions?
Reduce perinatal morbidity and mortality by promoting pulmonary maturity
DO not increase risk of infection, but additional insulin will need to be given to diabetic pts
What is tocolysis
Tocolysis involves using medications to stop uterine contractions. Nifedipine - CCB
Atosiban is an oxytocin receptor antagonist that can be used as an alternative when nifedipine is contraindicated.
Tocolysis can be used between 24 and 33 + 6 weeks gestation in preterm labour to delay delivery and buy time for further fetal development, administration of maternal steroids or transfer to a more specialist unit (e.g. with a neonatal ICU). It is only used as a short term measure (i.e. less than 48 hours).
Why should tocolysis be used when steroids are given?
steroids take 24 hours to work
How are infections detected / prevented to prevent preterm labour?
Sepsis required full evaluation and treatment - may occur even when membranes have not ruptured
Chorioamniotitis warrants IV antibiotics and immediate delivery
antibiotics should not be administered to non-infected women simply in threatened preterm labour as long-term cognitive impairment is increased
What is the effect of magnesium sulphate in preterm labour?
Neuroprotective for the neonate if given <12 hours 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 toxic in overdose
Where should extremely premature or small neonates be born?
Unit with NICU
What mode of delivery are best for preterm delivery?
Vaginal delivery reduces incidence of neonatal respiratory distress syndrome
C-section is only undertaken for the usual obstetric indications
Most preterm are in breech position, so C-section is common
Forceps rather than Ventouse
unless immediate neonatal resuscitation is required, the cord should not be clamped for 45 seconds to reduce neonatal morbidity
Antibiotics
Why are antibiotics recommended for preterm delivery?
Increased risk and morbidity of GBS
What is preterm prelabour rupture of the membranes?
When membranes rupture before labour at <37 weeks - often the cause is unknown, but all the causes of preterm about may be indicated
in how many preterm deliveries does preterm prelabour rupture of the membranes occur?
before 1/3 preterm deliveries
What are the complications of PPROM?
Preterm delivery = principal complication (follow within 48 hours in >50% cases)
Infection of foetus, placenta, chorioamnionitis) or cord (funisitis) is common - may occur before and be the cause or after the membrane rupture.
(earlier the gestation, higher the chance of 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 PPROM?
Gush of clear fluid - followed by further leaking
Pool of fluid in posterior fornix on examination = 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 - although clinical signs often appear late
What investigations should be done for PPROM?
‘Point of care tests’ are available in doubtful cases - but not entirely reliable
Sterile speculum: pool of fluid in posterior fornix = diagnostic
USS - reduced liquor? Volume can 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 the management of PPROM?
Risk of preterm delivery is balanced against risk of infection - the woman is admitted for at least 48 hours and given steroids and antibiotics
Close maternal and foetal surveillance is performed - if the gestation reaches 34-36 weeks, then normally delivery is undertaken
What is the management if there is evidence of uterine infection in PPROM?
IV antibiotics are given immediately and the foetus is delivered
Chorioamniotitis will not be eliminated by antibiotics alone
How is prevention of infection in PPROM treated?
Prophylactic use of erythromycin in women even without clinical evidence of infection is usual
Prophylactic Erythromycin 250 mg QDS for 10 days.
