Preterm Labour Flashcards
What is the definition of late preterm labour?
34-37/40
What is the definition of early preterm labour?
<34/40
What is the definition of very preterm labour?
28-32/40
What is the definition of extreme preterm labour?
<28/40
What proportion of PTB is iatrogenic?
20%
What are four possible mechanisms for spontaneous PTL?
- Premature activation of maternal or fetal HPA axis
- Exaggerated inflammatory response or infection
- Decidual haemorrhage
- Pathological uterine distension
What are the risk factors for PTB (20!)
Previous PTB (15-30% recurrence, usually at same gestation) Multiple gestation IVF Uterine anomaly including fibroids Previous cervical surgery PPROM Previous 2nd trimester abortion Polyhydramnios Genital tract infection Asymptomatic bacteruria Systemic infection Maternal chronic disease APH - 1st trimester / praevia / abruption Smoking Extremes of age Anaemia IUGR Fetal anomaly (or demise) Social factors Genetic factors
+ CS at fully
At what gestation (of prematurity) should you NOT do FBS and FSE?
< 34/40
What is bronchopulmonary dysplasia?
Oxygen requirement at 28 days old or at 36/40
Multi factorial
What is apnoea of prematurity?
Central, obstructed or mixed
Desaturation and bradycardia
Immaturity of central respiratory drive
Treat with caffeine
What is periventricular leukomalacia?
What is it associated with?
Hypoxia of watershed areas of brain white matter
Associated with cerebral palsy - spasticity and neurodevelopmental delay
What are 13 complications of prematurity?
RDS Apnoea of prematurity TTN BPD NEC PDA Feeding intolerance IVH PVL Sepsis
Hypothermia
Hypoglycaemia
Jaundice
What was the finding of the Cochrane review looking at
- prenatal administration of progesterone to prevent PT in women considered to be at risk of PT
Benefits in prolonging pregnancy and in infant health
`What was the finding of the Cochrane review looking at
- combinations of tocolytic drugs for inhibiting PTL?
Unclear whether combination therapy better than single tocolytic therapy
What was the finding of the Cochrane review looking at
- Calcium channel blockers for inhibiting PTL?
Benefits over placebo with regard to - prolongation of pregnancy - serious neonatal morbidity - maternal adverse effects but NO difference in perinatal mortality
Benefits over betamimetics, ORAs and MgSO4
What was the finding of the Cochrane review looking at
- antibiotics for asymptomatic bacteruria in pregnancy?
May be effective in reducing risk of pyelonephritis in pregnancy
MAY be a reduction in PTB and LBW with antibiotics
2019
What was the finding of the Cochrane review looking at
- antibiotics for BV in pregnancy
Can eradicate BV, but overall risk of PTB was not reduced
What was the finding of the Cochrane review looking at
- effect of umbilical cord clamping in PTB
Delayed, rather than early cord clamping may reduce the risk of death before discharge for babies born preterm
At 23/40, what are the
- survival rates
- survival without major/minor morbidity
Survival rate - 55%
Survival without morbidity = 2.3%
At 24/40, what are the
- survival rates
- survival without major/minor morbidity
Survival: 70%
Survival without morbidity: 0%
At 25/40, what are the
- survival rates
- survival without major/minor morbidity
Survival rate: 78%
Survival without morbidity: 2%
What is the mechanism by which steroids help lung development?
Accelerated development of Type 1 and 2 pneumocystis
Leading to structural and biochemical changes that improve lung mechanics and gas exchange
Increases surfactant production
Induce pulmonary beta receptors, induce antioxidants and promote lung fluid absorption after birth
Until what gestation, should you consider rescue / repeat dose steroids?
32+6/40
What is the role of steroids prior to El LSCS
Can use “if there is known fetal lung maturity” past 34+6/40 (vague)
Current recommendation in NZ is not to give unless CS <39/40
What were the findings of the Cochrane Review looking at antenatal corticosteroids for accelerating fetal lung maturation in women at risk of PTB
Sep 2020
Updated Dec 2020
Single course of steroids reduces
- respiratory morbidity
- NEC
- death (perinatal and neonatal)
Probably reduces
- IVH (previously in above category)
- developmental delay
NO effect on
- birth weight
- maternal Chorioamnionitis, endometritis, mortality
What were the findings of the Cochrane Review looking at antenatal corticosteroids for preventing respiratory compromise after CS at term?
May
- reduce respiratory problems
- reduce NICU admission
Further studies required
What were the findings of the Cochrane Review looking at repeat antenatal corticosteroid doses for women at risk of PTB, for preventing respiratory distress?
Repeat dose helps
- respiratory distress
- “other serious health problems”
What are the 4 proposed mechanism of action of Mg in fetal neuroprotection?
Stabilisation of cerebral circulation
Stabilising neuronal membranes
Anti-oxidant effects to reduce apoptosis
Anti-inflammatory effects
What effect does cervical cerclage have on PTB in
Women with an incidental finding of a short cervix?
Decreases RR 0.74
What effect does cervical cerclage have on PTB in
Women with a short cervix and previous history of PTB
Decreases, RR 0.61
What effect does cervical cerclage have on PTB in
Women with a short cervix and hx previous second trimester loss?
Decreases RR 0.57
RANZCOG’s statement on cervical length measurement at mid-trimester scan
Assessment of cervical-length at 18-24/40 in women at LOW risk of PTB should be considered
Accurately measured USS cervical length has an __________ relationship with the risk of PTB in low-risk asymptomatic women
Inverse
What is the cut off for a short cervix?
20 or 25mm, between 18-24/40
Apart from cervical length, what three cervical features on USS are associated with PTB
Funnelling: effacement of the internal aspect of the cervix
Shortening in response to fundal pressure or uterine activity
Intra-amniotic sludge
What is fetal fibronectin?
Fibronectin protein / glycoprotein produced by fetal cells, found at the interface of the chorion and the decidua
At what depth of LLETZ is there an increased risk of PTB?
10mm
At what gestation and situations should a rescue cerclage be considered?
16-27/40
Dilated cervix
Exposed, UNruptured fetal membranes
NICE guideline
When should prophylactic cerclage be considered?
Cervical length <25mm between 16-24/40
AND either previous PPROM / hx cervical trauma
When should prophylactic vaginal progesterone be considered?
Hx sPTB up to 34/40 OR mid-trimester loss
OR
TV USS between 16-24/40 with cervical length <25mm
Treatment should start between 16-24/40 and continue until 34/40
What is the mortality rate of NEC?
40%
What are fetal factors and clinical conditions that might increase the risk of adverse outcome in periviable preterm birth
Fetal factors
- male sex
- multiple pregnancy
- congenital anomalies
- fetal growth restriction
Clinical conditions
- PPROM < 24/40
- Chorioamnionitis
Until what gestation should rescue dose steroids be considered?
32+6/40
Maximum 3 doses
RANZOCG
