Fetal medicine Flashcards
Definition of FGR vs SGA vs IUGR
FGR = EFW <10%
SGA (isolated FGR) = physiologically small
IUGR = EFW <10%, abnormal dopplers/ AFI, poor growth velocity
Antenatal monitoring for those with known IUGR risk factors
Growth
AF
UAD from 26/40 every 2-4/52
Consider aspirin if risk factors present
Incidence and outcome of IUGR
Affects 10% pregnancies
Recurrence 25%
70% normal outcome
if EFW <3%, significant increase in adverse perinatal outcomes
Monitoring diagnosed IUGR
Growth scan every 2/52
If raised dopplers (PI > 95%) = increase monitoring to weekly, UAD every second week
AEDF <34/40 - admit, daily CTG, twice weekly AFI + UAD
REDF <30/40 - admit, daily CTG, AFI/ UAD 3x/week, +/- fetal med opinion
MCA and DV can be measured - not used for delivery timing
Delivery in IUGR
Consider timed steroids - 24-34/40 and up to 38/40 in some situations
AEDF - delivery </= 34/40 or sooner if poor growth/ dec AFI
Isolated FGR w normal LV/ UAD - deliver 37/40 or up to 38-39/40
If <32/40, consider MgSO4
Continuous CTG in labour w abnormal UAD, low threshold for CS
Cord gases and placenta for histology
MOD - individual basis decision. CS advised if AEDF or very PT
PN counselling if <34/40 - review of placenta and thrombophilia screen, future pregnancy plan
Women at high risk for pre-eclampsia
Hypertensive disease in prev pregnancy
Chronic kidney disease
Autoimmune disase
T1 or T2 diabetes
Chronic hypertension
Moderate risk factors for pre-eclampsia
First pregnancy
Age 40+
Pregnancy interval of >10 years
BMI >35
FH PET
Multi-fetal pregnancy
Definition of dopplers, absent end and reverse
Doppler: uses sound waves to determine flor and velocity of blood flow in a vessel, shift in observed frequency of a wave due to motion
AEDF - no flow towards fetus in diastole
REDF - blood flow away from fetus during diastole
Causes of abnormal dopplers
Maternal:
- medical dx
- prev SGA
- poor weight gain/ excessive exercise
- uterine anomalies
- ERT
Paternal:
- low birthweight
Fetal:
- female
- chromosomal
- malformations
- infections
- multiple fetuses
Placental:
- developmental abnormalities
- cord coil
- infarction
- villisitis
Risks to baby in the neonatal period with detected abnormal dopplers
increased risk CS
Low BSL after delivery
Hypoxia during delivery
Admission to SCBU
Meconium aspiration
Increased risk of motor and neurological abnormalities
Feeding difficulties
NEC
Sepsis
Fetal anaemia - definition
Normal fetal Hb shoudl increase throughout GA - 150g/L at 40/40
Anaemia: > 70g/L below mean for gestation
Hydrops zone - gestation dependent. Ranges from fHb <40g/L at 18/40 to fHb 80g/L at 40/40
Implications of fetal anaemia
Reduced tissue perfusion –> brain injury, cardiac failure, IUFD
Causes of fetal anaemia
MC: alloimmune red cell destruction
MC non-immune infectious red cell destruction - parvovirus
Others:
disorders of fetal red cell production
fetal haemorrhage
fetal tumours
complications of monochorionicity
Definition and incidence of red cell alloimmunisation
Haemolytic disease of the fetus and newborn (HDFN) - occurs after a woman is exposed to a mismatch of paternally derived RBC antigens from fetus
Affects 1 in 300-600 live births
RBC alloantibodies present in 1 in 80 pregnant women
Causes of red cell alloimmunisation
Sensitizing events
Blood transfusion
Types of rhesus antibodies
D, c, E K
D - antiD reduced D-alloimmunisation to 2%
Anti-E most prevalent
Rare - K (Kepp group) - can cause severe, early onset anaemia –> suppresses erythropoesis and RC destruction
If incompatibility with Rh D, c and E –> severe HDFN
Why does Rh affect second pregnancy and not the first
First responmse IgM can’t cross the placenta
Second response IgG - can cross, therefore affecting subsequent pregnancies
Antenatal screening for RC alloimmunisation
Booking and 28/40 G&H for antibody status
+/- fetal genotyping depending on unit
cffDNA - diagnostic for RC antibodies
Monitoring in cases with RC alloimmunisation
Blood test 4 weekly up to 28/40, then 2 weekly until delivery
Levels and titre measured
Kell AB - low threshold for referral
Prevention of alloimmunisation
RAADP prophylactic doses - 28/40, postnatally
AntiD within 72 hours of sensitizing event
1 500iu dose anti-D sufficient to cover 4ml of fetal RBCs
Kleihauer-Betke test confirms fetal-maternal haemorrhage (FMH)
Sensitization can occur with silent FMH, failure to administer antiD or if too small a dose given
Large FMH - needs 125u/ml
Max dose 10000units/day
Parvovirus spread and consequences
ssDNA virus
Spread via resp droplets
More than 1/2 population immune
Infection in first 1/2 pregnancy - fetal anaemia and hydrops - d/t viral destruction of fetal erythroid progenitor cells
Fetal loss: <20/40 - 13%, > 20/40 0.5%
CMV testing
Avidity testing - tests strength of IgG and antigen complex
Gradually increasing with time after primary infection –> latency of infection
Low acidity = recent infection
2% associated with reactivation after previous primary infection
USS signs of congenital infection
Echogenic bowel
Hepatic calcifications
Organomegaly
Dysplastic kidneys
Ventriculomegaly
FGR
Disorders of fetal erythropoeisis
Aplastic anaemia
Thalassaemia
Genetic disorders - porphyria, fanconi anaemia, G6PD
Vascular tumours
Fetomaternal haemorrhage
Vasa praevia
Monochorionicity - twin anaemia polycythaemia sequence
Barts hydrops fetalis
Complication seen in fetus born to two parents with alpha thalassaemia trait (1 in 4 major)
Occurs in the absence of any normal Hb
Classic US sign: thickened placenta
Fetal features:
- severe pallor, generalised oedema and massive HSM
- signs of fetal distress usually evident by third trimester
TAPS
Twin anaemia polycythaemia sequence
- occurs in monochorionic twins
- similar to TTTS but placental connections smaller
- small caliber AV anastomoses occur, typically near the edge of the placenta, <1mm in diameter
- normal AFI, unlike TTTS
Who to refer to fetal medicine- re RC alloimmunisation
Rising antibody titres/ above specific threshold
USS features
Unexplained severe neonatal jaundice/ anaemia with HDFN excluded
Ab other than anti-D, anti-C, anti-K
Hx prev significant HDFN/ OUT/ titre >/=32
Anti-D >4iu but <15 = moderate reisk/ >15iu = severe HDFN
ANti-c >7.5iu/ml but <30 = moderate risk/ >30 = high risk
Identifying fetus with fetal anaemia
High risk - booking hx, G&H, screening, USS
Diagnosis: direct fetal blood sampling
Doppler MCA-PSV - >1.5MoM = action
Hydrops: effusions, ascites, oedema, poly
MRI to estimate fetal haematocrit
CTG - sinusoidal pattern
Process of intrauterine transfusion
US guided percutaneous needle (2-22G)
via umbilical vein
Intraperitoneal fetal transfusion
Medical treatment fetal anaemia
IvIG - blocks transprt of alloantibodies across the placenta
Neonatal Outcomes assoc with fetal anaemia
cord bloods of at risk neonates - direct antiglobuylin test, Hb, bilirubin
Antibodies remain for 6 months - continuing RC destruction –> chronic unconjugated hyperbilirubinaemia and brain injury (kernicterus)
Early neonatal anaemia in HDFN (w/in 7/7)
Hydrops fetalis -
excess fluid in more than one body cavity - subcutaneous oedema, pleural effusion, pericardial effusion, ascites
Maternal risk factors for hydrops
Racial background
Prev pregnancy
Genetic FHx
Consanguity
Illness or contact with illness during pregnancy
Causes of hydrops
Isoimmunisation
Chromosomal - trisomies, turners
Anaemia - alpha thalassaemia, chronic FMH
Genetic
CVS - structural, tachyarrythmias
Pulmonary - diaphragmatic hernia
Cystic hygroma
Infections - parvo/ CMV/ syphilis/ coxI
Investigations in hydrops
Blood group and ab screen
Haemoglobinopathy screen
TORCH and parvo screen
Syphilis serologyu
Coxsackie
Kleihauer
US - other abnormalities, MCA doppler, amnio for karyotype and virology
Rh sensitizing events
Delivery
ERPC
CVS
Amnio
ECV
Miscarriage >12/40
APH
Treatment hydrops
IU transfusions for isoimmunisation and parve
Syphilis - hugh dose penicillin
Cox - resolve spontaneously
CMV - poor outcome
Tachyarrhthmia - antiarrhythmics
Termination - karyotyping
Incidence gastroschisis
1-6 per 10000
Incidence omphalocoele
1 in 4000-7000
Risk factors for omphalocoele
AMA>40
Obesity
Smokng
ETOH
SSRIs
What is an omphalocoele
Abdominal wall defect - bowel +/- other abdominal organs protrude within a thin layered sac, near the base of the umbilical cord
Defect usually 4-12cm
Differentials for omphalocoele
Gastroschisis
Cloacal extrophy
physiological gut herniation
Hernia of the cord
Aetiology of omphalocoele
in early pregnancy- organs form outside the body and return to the abdominal cavity by 11/40- failure–> omphalocoele
Not genetic; appears sporadic
Can be a part of a genetic syndrome
Defects associated with omphalocoele
Abdo, Cardiac, neuro, gu
Chromosomal abnormalities associated with omphalocoele
Trisomy 13, 18, 21
45XO
Klinefelter
Triploidy
Brockwith-Wiedeman syndrome
Pentology of Cantrell
OEIS complex
Types of omphalocoele
Small: bowel only
- associated with genetic syndromes - T18, T13, T21, Turners, aneuploidy
Large: includes other organs
- more likely associated with pulm hypoplasia, 1/3 also have cardiac anomalies
Diagnosing omphalocoele
Increased AFP in T1
USS + growth surveillance
Amnio/ NIPT
Fetal echo/ MRI
What is a Schuster procedure
Staged surgical repair for large omphalocoele
Risk factors for gastroschisis
Mat age <20
Smoking
Env exposures- nitrosamines
Maternal COX inhibitors (aspirin/ ibuprofen)
Definition of gastroschisis
Full thickness abdominal wall defect with no protective membrane. Direct intestinal exposure to amniotic fluid –> chemical reactions –> thick inflammatory film covering
Aetiology of gastroschisis
Exact mechanism unknown
- ?compromise vascular supply to anterior wall
- ?defect in the primordial umbilical ring
- ? abnormal involution of the right umbilical vein–> weakened point at risk of rupture