Lecture 16: Preterm Labour Flashcards
What is preterm?
<37 weeks
VPTB <32 weeks
EPTB <28 weeks
What is spontaneous vs indicated preterm birth?
Indicated is dr initiated because of threat to either mum or babe.
Spontaneous prematurity is a pathology of uterine quiescence
What are the possible pathological processess of premature baby?
Endocrine - fetal/maternal stress
Inflammation / infection
Decidual haemorrhage
Uterine distension
Leads to abnormal stimulation and thus labour
What possibly triggers the cascade leading to stimulation and labour?
Infammation Mechanical Hormonal Fetal (genomic/HPA) melatonin and circadian rhythms
What causes pre-term activation of HPA, and what are two examples?
Increased fetal or maternal stress -> Prem. activation of fetal HPA
i. e Uteroplacental vascular insufficiency (FGR or PET) and thus spon. PTB
i. e Maternal major psychological stress can activate HPA axis
What sort of infections can cause PTB?
- Ascending infection into membranes i.e STI
Degrades barrier of cervix and infiltrates around membranes -> Inflammation (i.e because of phospholipase A2 or endotoxins) (this inflam interferes with normal pathway, enhancing the processes)
How does decidual heamorrhage (Pathology) come about?
Damaged decidual blood vessels -> Retroplacental hematoma
Thrombin activation as part of the normal coagulation cascade.
- > Directly increases myometrial contractions
- > upregulates MMPs -> pprom
- > Inhibits expression of progesterone receptors i.e activates as progesterone withdrawal.
What are some causes of distension and what physiological changes do they cause that possible lead to labour?
- Multiple pregnancy
- Polyhydramnios
- Enhanced stretching
- Increased CAP
- Increased connexin 43
What is cervical insufficiency?
- Dilation or effacement without contractions (i.e conditions for labour)
- Usually previable loss
- Clercage may be helpful
Is there strictly one pathophysiology?
No they all interrelate i.e slide 14
What are the short term costs of preterm?
Many different impacts as it can cause probelms in all systems
Psychosocial and financial impact on parents and families.
Often forced speration due to treatments, hard to bond. Also might be maternal complications
What are the long term costs of preterm?
- Recurrent hospitalisations
- Neurodevelopmental disabilities i.e cognition, motor dificits, sensory impairment, behaviour or psychology
- Chronic health issues
- Adulthood might be insulin resistance, diabetes etc
What is viability?
GA where a baby can be resus’d at delivery and survive without significant morbidity ~23 weeks
What determiens perivaibility?
- GA
- Use of corticosteroids
- Sex
- Infection / rupture of membranes
Essentially though its lung development and being in a tertiary care centre
What are two pathologies of periviabiltiy babes:
- Bronchopulmonary dysplasia
- Resp. distress syndrome
Why are anenatal corticosteroids needed?
- Induce surfactant production to overcome the tension of water in lungs to breathe
- Other effects:
- > Reduce fetal lung fluid
- > Alter responsive to oxidative stress
What are the risk factors for preterm birth?
- Previous PTB
- Short interval between preg.
- INFECTION
- SMOKING AND SUBSTANCE ABUSE
- Cervical age
- Poor antenatal care
- Conditions where there is increased uterine stretch
What are the modifiable risk factors prior to pregnancy that might alter preterm risk?
- Decreased need for cervical surgery
- Optimise interpreg interval
- Optimise maternal health
What are modifiable risk factors in pregnancy that might alter preterm risk?
- Stop smoking/substances
- Screen and treat for STI / UTI
- Encourage prenatal care
- Decrease risk of PET (aspirin / Ca)
What are some biomarkers for preterm birth?
Many studies, non great in asymptomatic patients but:
FFN (Fetal fibronectic, fuses membranes)
- (present in cervico vaginal fluids in first trimester)
In combination with CL and history factors to improve sensitivity but still isnt great (CL - cervical length)
Whats a screening test for PTB?
Cervical length
CL at 16-24 weeks is proportionate to gestation at birth
BUT need to screen 1000 women to prevent six cases (treated with progesterone)
How else can we prevent PTB?
Modifiable social determinants of health i.e advocate
Otherwise:
- Progesterone
- Cervical clercage
- Preterm birth clinics for those at high risl
Do we know how cervical clercage works?
No
What does not work for PTB prevention?
- Maintainence tocolytics
- Untargeted antibiotics
- Relaxation therapy
- Bedrest
- Probiotics
If labour is predicted and you are preterm what can you do?
Use tocolysis to buy time in order to:
- Transfer to tertiary unit
- Antenatal corticosteroids
- MgSO4 for neuroprotection (against CP)
What drugs are for tocolysis?
Ca channel blockers
Oxytonin receptor blockers
B2 agonists
PG synthase inhibitors
If fetal fibronectin comes back positive…. what does in indicate?
30% deliver in 7-10 days
- ive 99.5% dont deliver
i. e should not be positive between 22-25 weeks)
How often do membranes rupture in preterm birth and what are the indications?
30% rupture in sPTB
- Membranes weakened
- Exposure of decidual tissue may increase PGS = labour
- Loss of barrier increases risk of infection
How do you treat premature membrane rupture and PTB?
- Erythromycin prolongs latency, reduces Resp. distress syndrome, major cerebral abnormalities
- Optimise fetal condition steroids, MgSO4, transfer to tertiary center and monitor for infection
- Aim to deliver at term
