Lecture 16: preterm birth Flashcards
What is preterm labour?
Labour before 37 weeks (about 9% of births)
very preterm is <32 weeks (about 2% of births)
It is an abnormality - a failure of uterine quiescence and a failure to keeo the baby in until the right time
Why is it a problem?
- neonatal conditions
- long term health costs
- individual and family costs
- Societal costs ($1500 per day in care)
Causes of preterm birth?
Cervical ripening consists of?
- Active inflammatory like process
- Infiltration of leukocytes
- Increase in cytokines and MMPs
- Independent of uterine activity
Triggers to ‘upset the peace’?
Infection -up vagina or in from the mothers blood
Stretch - membrane disruption or myometrial distension
Tisssue damage - especially the cervix
Placentation - growth of fetus, hormone-progesterone, PG release, Poor attchment or bleeding
Problems with premature birth process?
Immature fetus - often unwell
Often malpresentation (eg breech)
Often have maternal comorbidities
Often have complicated caesarean sections if performed
Risk of recurrence (likely to have another one)
Lung development in preterm babies?
The largest cause of death in preterm babies and ultimately controls the viability of the the baby
Type 2 cells produce surfactant to lower surface tension
Two classifications of preterm birth?
- 50% spontaneous - infection, fetal uterine or cervical abnorm.
- 50% iatrogenic - maternal disease, fetal health- FGR
Prediction risk assessement?
Previous PTB
smoking
multiple pregnancy
cervical surgery
uterine abnormality
maternal disease
Antepartum bleeding
What is fetal fibronectin?
- High MW glycoprotein “bio glue”
- Present in cervico-vaginal fluids in first trimester
- Seen in cervico-vaginal fluid of 20-30% women with preterm labour
- after 20 weeks up till 32 weeks its almost undetectable, unless something is going on (30% deliver in 7-10 days if high levels detected). If there is none then the chances of delivering are low (99.5% don’t in 7-10 days)
Drug used to supress preterm labour?
In NZ we just use nifedipine a calcium channel blocker
Ways of reducing negative neurological outcomes?
Magnesium sulphate - neuroprotetive
Aim for 6h before birth, 4g load and 1g/h for up to 24h (4h infusion is optimal) NNT to prevent 1 case of cerebral palsy : 63 women
Given under 30 weeks
Managing risk for preterm birth? Useful drugs in pregnancy?
Remove recurrent cause if possible
- Smoking (50% of preterm)
- Cervical cerclage next time (nylon stitch around cervix)
- drug therapies - progesterone
- Birth clinics being more aware
- Supportive social care
Aspirin and calcium in preterm because of growth restriction or preeclampsia respectively.
Use of progesterone in preterm pregnancies?
Serum levels don’t mesurably drop but it does seem to work
- Singletons but not multiple
- Effective in prior SPTB
- Effective in short Cx but not extremely short
- Role of P4 + cerclage some benefit
- injection may be unsafe or ineffective
- Not a tocolytic once contractions start
