Lecture 16: Preterm birth Flashcards
What is perterm labour?
Labour ebfore 37 weeks gestation
Very preterm = <32 weeks gestation
It is more than just dates.
Prematurity is an abnormality. It is a feailure of uterine quiescence.
A failure of the uterus to keep the bay in until the right time
What are some mechanisms of spontaneous preterm birth?
1) Intrauterine stretch (too much fluid?)
2) Intrauterine haemorrhage (premature cause of either inflammation - prostaglandin levels or membrane rupture)
- Endocrine maturation (‘stress’)
- Bleeding (placenta doesn’t stick properly, comes off uterine wall).
- Infection through bloodstream (septicaemia), vagina etc.
- Infection into amniotic cavity through blood stream (listeria monocytogenes is haematogenous spread).
- Loss of operculum (mucous plug) or short cervix (E.coli from bowl since perineum next to vagina anatomically)
- XS stretch (membrane disruption, myometrial distension)
- Tissue damage especially cervix
- Placentation (fetal growth, progesterone hormone, prostaglandin release, poor attachment, possible bleeding)
This is clinical risk prediction which guides management plan
What is involved in activation of labour?
- limited evidence suggesting wrong timing
- Activation involves
1) fetal genome
2) uterine stretch-growth
3) fetal HPA axis
4) upregulation of myometrium abnormally
5) cervical change primary or secondary
What are some triggers to upset the quiescent state?
1) infection
Inflammation/infections à withdrawal of ≥1 ( progesterone, PIG2, relaxin, PTHrP or NO) may predispose to labour or active imposition of stimulants or upregulation of key genes
2) stretch
- membrane disruption
- myometrial distension
3) tissue damage esp cervix
-e.g. due to surgeries
4) placentation
- growth of fetus
- hormone-progesterone
- prostaglandin release
- poor attachment-bleeding
Describe Prostaglandins and Labour
- Labour is activated
- Phospholipases release Arachidonic acid from cell membranes (lead to prostaglandin production)
- Increase myometrial contractility
- Lead to cervix changes
- Associated with membrane rupture
What are problems of preterm birth?
- Immature fetus are often unwell
- Often malpresentation e.g. breech
- Often have maternal comorbidities e.g. mum was sick
- Often have complicated caesarean sections
- Risk of recurrence
- __One complicated birth is often an indication of a complication again in the future births
- May have poor outcomes
_________ determines the limits of viability of preterm babies
Lung development
What are the 2 things that influence outcome in premature births?
1) Gestation (age)
2) Size
What disease is shown here?
Preeclampsia
This may lead to spontenous or iatrogenic early delivery
What are some predictors that are evident in the mother’s HISTORY for preterm birth?
History
1) Previous pre-term birth (highest risk- but previous preterm birth but ~50% population are nulliparous)
2) Smoking
3) Multiple pregnancy
4) Cervical surgery
5) Maternal disease *
What are some modifiable and non-modifiable risks for premature birth?
Non-modifiable risk
1) Maternal age
2) Obstetric history
Modifiable risk
1) SMOKING
2) No prenatal care
3) Need for cervical surgery
There are correlations between ________ length and preterm delivery
Cervical length
Shorter length ~ PPV
What can we screen for to predict pre-term births?
1) Cervical length
- shorter cervix ~ higher risk
2) Cervico-vaginal fluids
- qFN at risk
3) Serum biomarkers
- limited evidence
What is fetal fibronectin
Protein that sits between the chorion and the decidua
High MQ gylcoprotein: “Bio glue”
It is high in early pregnancy
from 20 to until 36 weeks in normal pregnancy, it is almost undetectable
If it’s high, it is indicative of preterm delivery risk.
Postiive test = 30% deliver in 7-10 days
Name 2 drugs used to supress preterm labour
Tocolysis
Nifedipine: Ca2+ channle blocker
Summary
Summary
