Problems of low birth weight Flashcards
What does ‘at term’ mean?
40 weeks
38-42
What is considered low birthweight?
<2500g
What is considered very low BW?
<1500g
What is considered extremely low birthweight?
<1000g
What is prematurity?
Birth before 37 completed weeks of gestation
What is small for gestation age?
- birth weight below 10th/3rd centile for gestation
What is fetal growth restriction?
Failure to achieve normal rate of fetal growth
Different from small for gestation as adverse effects causing this
May be full-term so grown to normal gestation but may be growth restricted making you small
Why may a baby be LBW?
- premature (early)
- small for gestation age (size)
- premature + SGA (too soon and too small)
- IUGR - something adversely affecting normal rate of growth
Why is LBW relevant?
Indicator of survival
What is the relevance of small gestation age?
- complications for fetal growth restriction
- very long term health problems
What is the relevance of premature birth?
- neurodevelopmental sequelae
What is the cause of SGA?
Genetic or acquired
What are the genetic causes of SGA?
- chromosomal disorders (Edwards, trisomy 18)
- inherited disorders
- normal small baby as parents are small
What are the acquired causes of SGA?
- utero-placental insufficiency
- congenital infection
- maternal smoking
- maternal chronic illness
- multiple pregnancy
What is utero-placental insufficiency?
- antenatally detected (poor growth)
- synctiotrophoblast invasion failure as highly resistant spiral arteries
- poor placental development with raised resistance in vascular bed
- Doppler ultrasound of uterine arteries/fetal circulation picks up (early diastolic notching)
- high resistance of uterine artery blood flow and reversal of flow
How does a hypoxic fetus present?
- prioritises blood flow to brain and cardiac muscle
- expense of gut, kidneys, aorta, adrenals, liver, skin
- Doppler ultrasound detects reduced uterine artery diastolic flow, reversed flow
What vessels are in the umbilical cord?
- 2 arteries
- 1 vein
What does CMV cause?
- hydrocephalus and calcification of the brain
- growth restriction
What maternal chronic illnesses can cause SGA?
- diabetes
- hypertension
- CHD
- stroke
- chronic bronchitis
(affect fetus cellular growth, gene expression, hormonal axis)
What neonatal problems can cause SGA?
- temperature control
- polycythaemia
- Hypoglycaemia
How can temperature control be impaired?
- increased SA;V ratio
- reduced adipose tissue insulation as inadequate nutrition
- reduced capacity for thermogenesis
How does polycythaemia occur?
Increased RBCs
- hypoxic in utero
- hyper viscosity = dangerous
How does hypoglycaemia occur?
- reduced glycogen reserves if preterm/inadequate trans placental nutrition
- urgent treatmentment = feeds, bolus of dextrose and IV infusion
- lethargy, fits -> neurodevelopmental risk
What are the 2 ways prematurity can occur?
- spontaneous preterm labour
- obstetrician delivers
What are the causes of spontaneous preterm labour?
- infection/ruptured membranes
- cervical incompetence
- polyhydraminios
Why may the obstetrician have to deliver the baby prematurely?
- save mother (hypertension/haemorrhage)
- save fetus (placental insufficiency)
but try to keep the fetus in utero as long as possible as uterus better than intensive care
What are the main problems of prematurity?
- temperature control
- respiratory - structurally and functionally immature/infection susceptibility
- cardiovascular
- nutritional
- infection
- neurological
Why is a premature baby at high risk of heat loss?
- large SA: body mass
- thin skin and less adipose tissue
- wet at birth and cannot shiver
- poor metabolic reserve
How is hypothermia avoided?
- modern incubators provide humidified warmth
- temp set to help baby maintain own temp at min. metabolic cost
- neutral thermal environment
- <26 weeks = deliver baby into polythene bag
- lower temperature = higher oxygen consumption
How may the respiratory system be structurally immature?
- primitive alveolar dev.
- susceptible to oxygen toxicity
How may the respiratory system be functionally immature?
- surfactant deficiency
- lack of respiratory drive
- intercostals and diaphragm weak
How may premature babies be susceptible to respiratory infections?
- immature immune system
- instrumentation of airway
What short term respiratory clinical problems are there?
- RDS
- pneumonia
- apnoea of prematurity (temp. cessation of breathing)
What is RDS?
- respiratory distress syndrome
- surfactant deficiency
- tachypnoea, expiratory grunting, recession
- within 4 hours of birth
How is RDS prevented?
- ante-natal steroids
- avoid intrauterine hypoxia
- prophylactic surfactant treatment
- keep warm, avoid acidosis
How is RDS treated?
- surfactant/respiratory support
What is chronic lung disease of infancy?
- bronchopulmonary dysplasia
- oxygen dependency in preterm baby
- lung injury by inflammation, fibrosis, emphysema
- low gestation prevalent
What is surfactant?
- monolayer of phospholipid molecules
- hydrophobic tails, hydrophilic heads
- reduces surface tension around alveoli keeping them open
- contains DPPC and PG
- stabilised by surfactant protein B
What is PG?
Phosphatidylglyercol
What are the cardiovascular problems of prematurity?
- PPHN (persistant pulmonary hypertension of the newborn, lung vessels don’t relax so are constricted and blood flow Is suboptimal)
- failure to maintain bp
- patent ductus arteriosus
How much energy do you need to grow?
- need 110-135 kcals to grow
- mature human milk is 68 cals/100ml
- if gut is immature gut will not absorb it so need to feed and:
- need to fortify milk
What are the nutritional problems of prematurity?
- immature suckling: enteral feeding required
- baby not fed = gut mucosa atrophies = poor gut motility
- excess feeding = precipitate necrotising enterocolitis
What is necrotising enterocolitis?
- acute bacterial invasion/inflammation/necrosis of bowel with bowel gas formation in bowel wall (pneumotosis)
What are the RF of necrotising enterocolitis?
- prematurity
- hypoxia
- infection
- enteral feeding
How is necrotising enterocolitis presented clinically?
- abdominal distension, tenderness, discolouration
- blood in stools
- generalised collapse
How is necrotising enterocolitis treated?
- stop feeds
- give antibiotics
How hospital acquired infections may the mother get?
- coagulase negative staphylococci
- gram negative organisms (colonise intestine)
What problems in pregnancy may cause infections?
term babies:
- transplacental IgG in 3rd trimester
- IgA and immunologically active cells in colostrum
- skin barrier
- acquisition of normal flora from mother and family
Preterm baby:
- denied this protection
- nursed in bacteriologically hostile environment
- given broad spectrum antibiotics
- invasive procedures breach host defences
What neurological problems can happen in prematurity?
- susceptibility to periventricular haemorrhage (poor control of brain perfusion, if sudden increased flow)
- risk of periventricular leukomalacia (ischaemia of periventricular white matter)
What are the risk factors of periventricular haemorrhage?
- prematurity
- RDS
- pneumothorax
- acidosis
- hypercapnia
- hypotension
- instability and handling
- severe bruising at birth
Is a symmetrical or asymmetrical baby worse?
Symmetrical as means brain and body are being spared of circulation so both small whereas asymmetrical means only abdominal organs spared and brain needs it more so function not impaired
How many LBW babies be associated with adult disease?
Barker hypothesis
- diabetes
- hypertension
- CHD
- stroke
- chronic bronchitis
Fetal environment can affect cellular growth/gene expression and hormonal axes
How can we protect preterm baby from infection episodes?
- disinfect hands and objects
- limit antibiotic usage
- trials of immunoglobulins, probiotics etc.
What are the complications of intracerebral bleeding?
- collapse and death
- loss of brain parenchymal tissue with cyst development
- CSF circulation blockage = hydrocephalus
