Problems of Low Birth weight and prematurity Flashcards
what is the median birth weight
the median UK birth weight at term (40 weeks)
what is term
40 weeks
what is the weight for
- low birth weight (LBW)
- very low birthweight (VLBW)
- Extremely low birthweight (ELBW)
Low Birthweight (LBW) = <2500g.
Very Low Birthweight (VLBW) = <1500g
Extremely Low Birthweight (ELBW) = <1000g.
what is prematurity
• Birth before 37 completed weeks of gestation
what does small for gestational age mean (SGA)
= Birth weight below the 10th/3rd centile for gestation
what is fetal growth restriction (FGR/IUGR)
failure to achieve normal rate of fetal growth (e.g from uteroplacental insufficiency or fetal infection)
what can cause Foetal growth restriction
uteroplacental insufficiency or fetal infection
why might a baby have a low birth weight
• Baby born too soon = premature.
o Note that baby can be the appropriate weight for gestation.
- Baby born too small = SGA (small for gestational age)
- Baby born too soon and too small = premature + SGA.
in order to diagnose growth restriction what do you need
- in order to diagnose growth restriction you need serial measurements of growth over the course of pregnancy
why is low birth weight important
- low birth weight is important as it indicates the chance of survival of the infant
what can happen if you are small for gestational age
- Complications of fetal growth restriction.
* Very long term health problems.
what can happen if you are premature
- Problems of prematurity- organs not ready for outside world
- Neurodevelopmental sequelae
the more premature you are…
the higher the mortality
what are the two reasons why a baby can be small for gestational age
genetics
acquired
describe the genetic and acquired reasons for a small for gestational age
Genetics • Normal small baby • Chromosomal disorders. o Edwards syndrome o Trisomy 18. • Inherited disorders.
Acquired
- Uteroplacental insufficiency - this is the most common
- congenital infection such as CMV
- smoking
- maternal chronic illness such as renal or sickle cell disease
- multiple pregnancy
What chromosomal disorders can cause you to be small for gestational age
o Edwards syndrome
o Trisomy 18.
How does utero-placental insufficiency happen
o Failure of syncytiotrophoblast invasion of the high resistance spiral arteries.
o Poor placental development with raised resistance in vascular bed.
How can you detect utero placental insufficiency
o May be detected antenatally because of poor growth.
Can be picked up using Doppler ultrasound of the uterine arteries/fetal circulation.
• Impaired placentation will impact uterine artery blood flow.
o Detects high resistance.
what happens in the hypoxic foetus
- this is when the foetus prioritises blood flow to the brain and cardiac muscle
- therefore there is a reduction in the blood going to the kidneys, gut, adrenals, liver and skin
- this causes an asymmetrical IGUR
describe what the umbilical cord is made up of
2 arteries
one vein
How can you detect a hypoxic foetus
• Can be detects by Doppler ultrasound.
o Reduced/reversed UA diastolic flow.
name some maternal chronic illnesses that can impact foetal growth
• Maternal chronic illness (renal, sickle cells disease)
o Diabetes
o Hypertension
o Coronary Heart Disease
o Stroke
o Chronic Bronchitis.
The fetal environment of these affect cellular growth/gene expression/hormonal axis.
How does CMV effect growth
Hydrocephalus and calcification of the brain.
Baby will also likely have growth restriction.
Name some problems that neonates have if they are small for gestational age
- temperature control
- polycythemia
- poor nutritional status
- hypoglycaemia
- increased risk of necrotising enterocolitis
why do small for gestational age babies have problems with temperature control
- they have an increased surface area to volume ratio meaning that it is easier for them to lose heat
- they have a reduction in brown adipose tissue due to inadequate nutrition
- they also have a reduced capacity for thermogenesis
what do small for gestational age babies have polycythaemia
- this is an increase in the number of red blood cells
- they increase the number of red blood cells so they can carry more oxygen this is because they are hypoxic in utero
- this can be a problem when they are born as it can cause hyperviscosity
why are small for gestational age babies hypoglycaemic
- this is because they are born with reduced glycogen reserves and there is inadequate trans placental nutrition
how do you treat hypoglycaemia in small for gestational age babies
Feeds
Bolus of dextrose + IV infusion if very low glucose
what are the symptoms of hypoglycaemia that small for gestational age babies can show
- lethargy and fits
- this has a risk of adverse neuro-developemental outcome
what is hypoglycaemia defined as in neonates
having less than 2.6mmol/l
what can low birth weight be associated with
- Low birth weight associated with adult disease (Barker hypothesis)
- Diabetes
- Hypertension
- Coronary Heart Disease
- Stroke
- Chronic Bronchitis
- Explored in human and animal studies
- Fetal environment affecting cellular growth, gene expression and hormonal axes
What are the causes of premature babies
- spontaneous preterm birth
- delivered by an obstetrician
why do spontaneous preterm births happen
- Infection or ruptured membranes
- Cervical incompetence
- Polyhydramnios
what can cause an obstetrician to deliver a preterm baby
- To save mother (Hypertension, Haemorrhage)
* To save fetus (Placental insufficiency)
what are the problems of prematurity
Temperature control Respiratory Cardiovascular Nutritional Infection Neurological Long term sequelae
why is a preterm baby at high risk of heat loss
- Large surface area : body mass ratio
- Thin skin and less adipose tissue
- Wet at birth
- Can’t shiver
- Poor metabolic reserve
hypothermia is a …
independent predictor of death and morbidity among survivors that initially survive delivery
How do you avoid hypothermia in preterm babies
- in order to avoid hypothermia you have to provide warmth and humidity to avoid transdermal heath loss therefore you place them in an incubator which provides humidified warmth
- the temperature of the humidifier should be the natural thermal environment which is the temperature that is used to help the baby maintain temperature at minimal metabolic cost
- the baby is less than 26 weeks old then the baby can be delivered into a polythene bag up to the shoulders to prevent evaporative heat loss
what is the natural thermal environment
temperature that is used to help the baby maintain temperature at minimal metabolic cost
what can be done to prevent heat loss in a baby who Is less than 26 weeks old
- the baby is less than 26 weeks old then the baby can be delivered into a polythene bag up to the shoulders to prevent evaporative heat loss
the lower the temperature…
the higher the oxygen consumption
what are the 3 main respiratory problems
- structurally immature
- functionally immature
- susceptibility to infection
why are preterm babies respiratory system structurally immature
Primitive alveolar development.
Susceptibility to O2 toxicity.
what are preterm babies respiratory system functionally immature
Surfactant deficiency - can’t defend against the alveoli tension
Lack of respiratory drive
• Intercostals and diaphragm weak.
why are premature babies respiratory system susceptible to infection
Immature immune system.
Instrumentation of airway. - e.g. mechanical ventilation used can provide an easy way for pathogens to enter
what are the short term respiratory clinical problems in a preterm
- Respiratory distress syndrome
- Pneumonia
- Apnoea of prematurity – temporary cessation of breathing
what are the long term respiratory clinical problems in a preterm
chronic lung disease of infancy
what causes respiratory distress syndrome
• Caused by lack of surfactant in the premature baby
how do you diagnose respiratory distress syndrome
clinical, radiological or post-mortem
what are the symptoms of respiratory distress syndrome
tachypnoea
expiratory grunting
recession
- happens within 4 hours of birth
How do you prevent respiratory distress syndrome
- Ante-natal steroids
- Avoidance of intrauterine hypoxia
- Prophylactic surfactant treatment
- Keep warm, avoid acidosis – acidosis can denatures surfactant
what is the treatment of respiratory distress syndrome
- Surfactant
* Respiratory support
name examples of chronic lung disease of infancy
bronchopulmonary dysplasia: BPD
What happens in chronic lung disease of the infancy
Oxygen dependency in a preterm baby at 36weeks post menstrual age
Lung injury in the preterm infant
Inflammation, fibrosis, emphysema
prevalence in chronic lung disease of the infancy raises in ..
low gestations
Describe the structure of surfactant
- there is a monolayer of phopholipids at the air liquid interface in the alveoli
- this reduces the surface tension around the alveoli and keeps them open
- the surfactant consists of Dipalmitylphosphatidylcholine (DPPC) & Phosphatidylglycerol (PG)
- it is stabilised by surfactant protein B
what are the two things that surfactant is made out of
DPPC and PG
what stabilises surfactant
Surfactant protein B
name three cardiovascular defects that the preterm baby can have
- PPHN - Persistent pulmonary hypertension of the new-born
- Failure to maintain Blood Pressure
- Patent Ductus
what are the nutritional needs of the baby
- Preterm baby needs 110-135 kcals/kg/d to grow
- The calorific content of mature human milk is ~68 cals/100ml
- 160-200 ml/kg/day of milk may be required to generate growth
- Can fortify milk to increase protein, calorie and mineral content
if the baby cannot tolerate milk what can you give instead
can give intravenous parenteral nutrition
why in a preterm baby is the gut not ready to take milk
the vili the brush border enzymes are not ready therefore it is important to give milk early on to start to upregulate the intestinal hormones and maintain the brush border enzymes
what are the problems with feeding
- the baby might not be able to suckle
- if the baby cannot feed this leads to gut mucosa atrophies and can cause poor gut motility
what can excess ending show
- excess feeding may precipitate necrotising enterocolitis
What is necrotising enterocolitis
Acute bacterial invasion/inflammation/necrosis of bowel with gas formation in bowel wall (pneumotosis)
What are the risk factors for necrotising enterocolitis
- prematurity, hypoxia, infection, enteral feeding
what are the signs and symptoms for necrotising enterocolitis
- abdominal distension, tenderness, discolouration
- blood in stools
- generalised collapse
how do you treat necrotising enterocolitis
stop feeds, give antibiotics, +/- surgery
what are the complications of necrotising enterocolitis
- death (~25%)
- short gut secondary to resection
- strictures and late obstruction
what are bacterias that cause early infection (less than 48 hours)
- Group B beta haemolytic Streptococcus
* E. coli
what are common hospital acquired infections (greater than 48 Hours)
- Coagulase Negative Staphylococci
* Gram negative organisms that colonise the intestine
what are the immunological benefits of being a term baby that you miss out on being preterm
Transplacental IgG in third trimester – misses out on this
IgA and immunologically active cells in colostrum – not getting breast milk miss out on immunologically cells
Skin barrier – don’t have enough dermis so they can get things going in, have tubes and lines in which bacteria can get in
Acquisition of normal flora from mother and family
What other infection problems are there for the preterm baby
o Less trans placental IgG in third trimester.
o Lie in bacteriologically hostile environment
o Antibiotics: kills the “good bacteria” from mother
o Invasive procedures.
How can we protect the preterm baby from episodes of infection
- Disinfect hands and objects!
* Limit antibiotic usage – range of drugs and duration of treatment
what is the preterm central nervous system at risk of
Periventricular Haemorrhage (PVH)
Periventricular leucomalacia (PVL)
Why is the preterm/short term central nervous system at risk of a periventricular haemorrhage
Periventricular Haemorrhage (PVH)
- this is because there is poor control of brain perfusion
- if there is a sudden increase blood flow then this can cause a periventricular haemorrhage
why is the preterm/short term central nervous system at risk of a periventricular leucomalacia
• Ischaemia of periventricular white matter.
what are the risk factors for a periventricular haemorrhage
- Prematurity (very rare after 34 weeks)
- RDS
- Pneumothorax
- Hypercapnia
- Acidosis
- Hypotension
- Instability and handling
- Severe bruising at birth
What are complications of intracerebral bleeding
- Collapse and death
- Loss of brain parenchymal tissue with cyst development (single porencephalic cysts, multiple = periventricular leucomalcia)
- Blockage of CSF circulation leading to hydrocephalus
what is the long term effect of prematurity on the brain
Long term can lead to cerebral palsy as well as cognitive and behaviour problems.
what are long term effects of prematurity on the retina
- Retinopathy of Prematurity, ~15% below 26w, can be treated with laser
