Prematurity/ IUGR Flashcards
define low birthweight?
birthweight less than 2500g
define preterm baby?
baby born less than 37 weeks gestation
define extremely preterm baby?
baby born less than 28 weeks gestation
define very low birthweight?
birthweight less than 1500g
define ‘small for gestational age’?
birthweight less than 10th centile for age and gender
what are some causes of babies who are small for gestational age?
maternal factors- CHD, HT, renal disorders, drugs, malnutrition, smoking etc
fetal factors- congenital infections, chromosomal abnormalities (trisomy 18), structural malformations
placental factors- multiple pregnancies (twin twin transfusion syndrome), preeclampsia, thrombophilia, placental insufficiency
what does twin-twin transfusion syndrome refer to?
unequal sharing of uteroplacental vascularity between twins
what is the most common cause of preterm birth?
idiopathic- no known cause
what are some known causes of preterm birth?
premature rupture of membranes Cervical incompetence Multiple pregnancies Uterine anomalies antepartum haemorrhage
define IUGR?
failure of the fetus to achieve its growth potential
why is UPD (uniparental disomy) bad for fetuses?
inheritance of both chromosomes from one parent–> increased risk of autosomal recessive diseases
what perinatal infections can cause IUGR and how would you prevent them?
-CMV and toxoplasmosis are the two infections which cause IUGR
prevent CMV and toxo with good handwashing!!
avoid gardening and stray cats for toxoplasmosis
what are some ways we can detect IUGR?
Symphyseal-Fundal Height (SFH) MEASUREMENT
Ultrasound at 34 weeks, look at abdominal circumference of baby but not routinely done unless high clinical suspicion
you look at an ultrasound and notice that the foetus appears small. how might you exclude small foetus due to genetics rather than IUGR?
Parental small stature, absence of recognised risk factors, symmetrically small, normal growth trajectory, normal amniotic fluid, normal umbilical and other Doppler studies
if a baby is born prior to 30 weeks, what must we give the baby urgently??
CORTICOSTEROIDS IF LUNG IMMATURITY, + NEUROPROTECTION WITH MAGNESIUM SULFATE
what is your general management of IUGR?
- Confirm the diagnosis- IUGR or genetically small? (do an u/s and look at features that may indicate the fetus is meant to be genetically small
- Look for a cause- take a good history!! Then Ix: tertiary U/s, FBE, UEC, anti-phospholipid syndrome, congenital thrombophilia, serology etc
Karyotyping! - Fetal surveillance- cardiotography and ultrasound
- Any treatment can we offer?? not much of the way of treatment
- Deliver the baby according to risk benefit analysis; e.g. emergency c section if signs of fetal hypoxia
why might we perform an expensive karyotype of a fetus with IUGR?
karyotyping –> avoid unnecessary emergency caesarean for fetal distress;
psychological effects for parents
?termination, if the prognosis isn’t apparent in late pregnancy e.g. CMV infection; twins discordant for fetal abnormality
what are some causes of preterm labour?
pre-eclampsia perinatal infection premature rupture of membranes smoking antepartum haemorrhage
what fetal biomarker can we use to predict preterm labour?
fetal fibronectin detected via cervicovaginal swab test
what is a typical clinical presentation of a pregnant women who is going through preterm labour?
the woman will usually report increased frequency of uterine contractions and or a sudden loss of fluid through the vagina (i.e. membrane rupture) and or sudden increase in vaginal discharge (displaced cervical mucous plug)
how might we suppress premature uterine contractions?
use of a tocolytic agent such as nifedipine (most commonly used), indomethacin, and oxytocin receptor antagonist atosiban
previously we used to use salbutamol
what are some adjuvant drugs we can use in preterm labour other than those that suppress uterine activity?
magnesium sulfate IV can be given to minimise risk of cerebral palsy in infant
maternal antibiotics in some cases may be indicated if infection present
what are the SE of nifedipine used in suppressing preterm labour?
calcium blockers like nifedipine can cause hypotension
what are some contraindications to b-adrenergic tocolysis (as in, to NOT suppress premature uterine contractions) in preterm labour?
when the gestation period is less than 20 weeks and or more than 32 weeks
maternal pre-eclampsia, CVD, bleeding placenta praevia, intrauterine sepsis, rupture of membranes, placenta abruption, fetal growth restriction, maternal hypertension
a baby is unexpectedly born at 30 weeks. what do you do?
keep them PINK, WARM, SWEET
Pink- maintain good O2 saturations
Warm- maintain body temperature
Sweet-maintain blood glucose
what are the long term consequences of giving a preterm baby supplemental O2 to help them breathe?
- lung injury from barotrauma (e.g. pressure from O2 delivery and ventilation–> chronic lung disease) or a pneumothorax
- retinopathy of prematurity
how might we prevent retinopathy of prematurity, caused by excessive O2 supply to a preterm infant?
in a preterm infant less than 32 weeks gestation, aim for O2 saturations between 88-92%.
For infants closer to full term, then we can use 100% O2
how might we maintain the body temperature of a preterm infant in NICU?
incubator, radiant warmer, reduce heat losses, regular axilla temperature monitoring
what BGLs are we aiming for in a preterm infant?
BSLs greater than 2.5mmol/L
how would you maintain adequate blood glucose levels in a preterm infant in NICU?
IV 10% dextrose without electrolytes 60mls/kg per day (divide by an hourly rate)
If you can’t put a drip in then use enteral breastmilk (e.g. colostrum)
what are the main causes of preterm infant death?
less than 28 weeks gestation:
hyaline lung membrane disease
sepsis
malformations
> 28 weeks gestation to 37 weeks:
sepsis
why are tocolytic agents helpful in managing preterm labour?
- helps to delay preterm labour until the mother is transported to an appropriate tertiary facility
- helps to delay preterm labour such that corticosteroids can be given –> prevents complications from lack of surfactant in fetal lungs
define cervical incompetence?
painless cervical dilation in the 2nd trimester causing preterm labour
what is the most common cause of respiratory distress in a preterm infant?
hyaline membrane disease- most common
how does surfactant deficiency cause respiratory distress in a preterm infant?
increased surface tension–> atelectasis–> reduced VQ perfusion–> asphyxia –> pulmonary vasoconstriction –> lung damage
what are the typical blood waveform patterns for an fetus with IUGR on doppler u/s?
The UmA often shows increased resistance from the
placenta as an early change. The MCA may show
reduced resistance as the baby diverts blood with
nutrients and oxygen to the brain. The DV may
show signs of dilatation as it diverts blood away
from the liver.
is growth scans accurate after 28 weeks?
NO
who should receive antenatal corticosteroids?
Antenatal corticosteroids should be given to all women at risk of iatrogenic or spontaneous preterm birth up to 34+6 weeks of gestation.
Antenatal corticosteroids should be given to all women for whom an elective caesarean section is planned prior to 38+6 weeks of gestation.
what corticosteroids do we use during the antenatal period in anticipation of early labour?
Betamethasone (Celestone) 12 mg given intramuscularly in two doses or dexamethasone 6 mg given intramuscularly in four doses are the steroids of choice to enhance lung maturation.
what is the difference between asymmetric and symmetric growth restriction in an IUGR fetus?
If growth of the head has been preferentially maintained (asymmetric growth restriction), the head appears inappropriately large for the body
There is relative sparing of the head circumference (and usually length) when plotted on growth charts.
This pattern suggests that the growth has been limited in the latter parts of pregnancy, often due to placental insufficiency.
Symmetrical growth restriction, on the other hand, is identified by a global reduction in growth parameters.
A growth-restricted infant whose head, length and weight are all affected implies issues beginning early in fetal development.
what is the pathophysiology of retinopathy of prematurity?
immature retinal vasculature, which normally develops in a centrifugal pattern from the optic disk outwards, is exposed to high partial pressures of oxygen in the blood.
Hyperoxia leads to retinal vasoconstriction and if this is prolonged, ischaemic damage occurs.
This is followed by a proliferative phase of growth of abnormal new vessels from the retina into the vitreous humour.
In severe cases, haemorrhage and oedema ensue and in the resulting organisation, fibrous scarring and retinal detachment may occur.
what are the complications of necrotising enterocolitis?
bowel perforation in the acute phase
short bowel syndrome in the long term
what might you consider if you saw a premature infant with abdominal distension, poor feeding and bloody stools?
necrotising enterocolitis
what prophylactic antibiotics do we use for PPROM?
erythromycin +/- amoxicillin/augmentin
what ix might we do to confirm PROM?
pH test—Nitrazine sticks/test (Amnisure) to detect high pH (liquor, mucus, semen, serum) cf. low pH (vaginal discharge, urine)
Pyridium test: dyes urine so can tell between urine and amniotic fluid
Ferning test: if positive (i.e. amniotic fluid) –> ferning because of high oestrogen content
what maternal ix might we order for confirmed PPROM?
FBE, CRP, WCC, blood group
GBS swabs
Endocervical swabs
MCS
