prematurity 2

Question 1

define premature birth?

Answer 1

born before 37 weeks 
extreme = <28wks 
very = 28-31wks 
moderate = 32-33wks 
late = 34-36wks

Question 2

define low birth weight infants?

Answer 2

<2500g at birth regardless of gestational age
LBW = <2500g
VLBW = <1500g
ELBW = <1000g

Question 3

where are the highest areas of preterm birth?

Answer 3

USA, Brazil, china, india

Question 4

what are some complications of prematurity?

Answer 4

sepsis
resp = RDS 
cardiovascular = PDA 
gastrointestinal = NEC 
metabolic 
sensory = ROP
IVH and white matter injury 
cerebral palsy, euro-developmental delay 
ADHD and behavioural problems 
failure to thrive 
insulin resistance, HTN

Question 5

what is the physiology of labour?

Answer 5

fetal and maternal signals -> inflammatory pathways -> cervical and membrane remodelling -> myometrial contractions

Question 6

what are the main aetiology of preterm birth?

Answer 6

indicated
spontaneous
PROM

Question 7

what are the pathological triggers for preterm birth?

Answer 7

uterine overdistenstion = multiples, poyhydraminos
infection = chorioamnionitis, UTI
ischaemia = inadequate trophoblast invasion, placental abruption
immunological triggers
cervical disease = following colposcopy treatment
hormonal changes = progesterone deficiency
pathological activation of the pathway to delivery

Question 8

what are the routes of intrauterine infection?

Answer 8

ascending route = commonest
haematogenous - via placenta
retrograde seeding via Fallopian tubes
iatrogenic following invasive procedure

Question 9

what is the mechanism by which infection causes preterm labour?

Answer 9

multiple mechanisms at play
cytokines play important role - IL1beta and TNF alpha = pro inflammatory. IL10 = anti-inflammatory
redundancy within CK network blocking one mediator appears insufficient to stop PTL

Question 10

what are the defences in the reproductive tract to infection?

Answer 10

acid vaginal pH 
cervical mucus 
epithelial barriers
innate immune system receptors (TLRs) 
problems with these can increase infection and risk of PTL,

Question 11

how does ischaemia cause preterm birth?

Answer 11

unclear mechanism, ?RAAS role

severe ischaemia may act via thrombin (with decimal necrosis/haemorrhage)

Question 12

how does cervical insufficiency cause preterm labour?

Answer 12

premature cervical ripening = mid-trimester pregnancy loss

more likely to occur n patients with anatomically distrust cervices - post LLETZ, congenital abnormalities

Question 13

how does endocrine disorders (progesterone deficiency) cause preterm birth?

Answer 13

progesterone promotes uterine quiescence, reduces CAP expression, inhibits cervical ripening, reduces inflammatory cytokines and CRH levels

Question 14

how does uterine over distension cause preterm birth?

Answer 14

increased expression of contraction associated proteins = gap junction proteins, oxytocin receptors, protein in PG synthetic pathway -> increase PG release
higher levels of collagenase ad IL8 in membranes

Question 15

what are the risk factors for preterm birth?

Answer 15

pervious preterm birth
multiples 
previous cervical surgery 
uterine anomalies 
smoking 
race 
age 
bacterial vaginosis 
short cervix on US

Question 16

how is preterm birth predicted?

Answer 16

current methods = 
history assessment 
US cervical length 
predictive bedside tests = fetal fibronecnin and actin partus 
infection screening - HSV, MSU 
clinical diagnosis 

future posibilites =
serum biomarkers
impedance spectroscopy
other cervical techniques

Question 17

how can cervical insufficiency be treated?

Answer 17

cervical cerclage = placement of suture to help prevent dilation of cervix

Question 18

what is fetal fibronecnin?

Answer 18

extracellular matrix protein found in choriodecidual interface
abnormal finding in cervicovaginal fluid after 20wks

Question 19

when is infection screened for?

Answer 19

12wk appointment

Question 20

when are antibiotics used to prevent preterm labour?

Answer 20

PROM - reduces mortality of neonate

but increased NEC wit co-amoxiclav

Question 21

what are some secondary prevention methods for preterm labour?

Answer 21

steroids ( accelerates development of type1 and 2 pneumocystis in fetal lung, increases alveolar epithelium sodium channels allowing resorption from fetal lung, inroad surfactant
tocolysis (nifedipine CCB, atosiban oxytocin receptor antagonist)  - delay delivery by a week gives time to give steroids, 
magnesium sulphate (neuroprotection)