intrauterine growth restriction max brinsmead mb bs phd august 2014
TRANSCRIPT
The fetus is unique because... He or she cannot signal his or health by
way of any history And we can only examine through his or
her mother We can only...
Document size and growth Evaluate his or her movements Listen to his or her heart Evaluate the fluid around him or her Assess his or her reaction to stimuli
When the uterus is SFD you first need to know…
What is normal
SFH = Weeks of gestation is valid only between 20 and 32 weeks
Thereafter the mean runs off to 37 cm at 40 weeks
This should be validated in each population
And the 95% confidence limits are not less than +/- 3 cm
When the uterus is SFD you also need to know DATES accurately…
Ultrasound is unreliable when… It is done by a non expert or with poor
equipment It is done late in pregnancy There is something wrong with the fetus e.g.
microcephaly
If the uterus is SFD think of…
Wrong dates Oligohydramnios
Premature rupture of membranes Abnormality of the fetal renal tract Intrauterine growth retardation (IUGR)
Intra uterine growth retardation There are two major categories Symmetrical = head, trunk and body reduced
proportionaely Asymmetrical = head-sparing growth restriction
Causes of Symmetrical IUGR
Constitutional smallness Consider maternal size Ethnic origin Paternal influence less important
Fetal Infections TORCH = Toxoplasmosis, Other, Rubella,
Cytomegalovirus and Herpes Remember Syphilis, HIV and Malaria
Fetal Abnormalities Especially chromosomal abnormalities such as
Trisomy 21, 13&16
Asymmetrical Growth Restriction
Occurs because the hypoxic baby will redistribute its cardiac output
From glycogen storage (liver size) From the kidneys (oligohydramnios) From the trunk and limbs From the bowel (meconium) And it does this to maintain blood
flow to the head, brain and heart
Causes of Asymmetrical IUGR
Anything that reduces Maternal-Uterine-Placental to Fetus transfer of oxygen and nutrients
Maternal smoking and malnutrition Severe maternal anaemia Chronic maternal disease Maternal hypertension especially pre eclampsia Uterine malformations Some placental diseases Maternal thrombophilias congenital or acquired Recurrent antepartum haemorrhage An idiopathic group
Diagnosis of IUGR
Only 30 – 50% will be detected by measuring SFH
Serial measures more valuable than a single one
We need to have a high index of suspicion in a fetus at risk
Hypertensive disorders Recurrent APH Poor obstetric history Multiple pregnancy
And use ultrasound selectively to confirm or exclude the diagnosis
A SFD uterus is more serious when…
The mother was underweight to begin with
She has not gained weight appropriately
There is a past history of IUGR or pregnancy loss
A condition known to be associated with IUGR is also diagnosed
Pre eclampsia Recurrent APH Chronic maternal disease or anaemia
Management of the SFD baby
Accurate diagnosis Is the baby salvageable? Mother at risk?
Steps that improve M-U-P-Fetal transfer of oxygen and nutrients
Stop maternal smoking Bed rest Correct anaemia Improve nutrition
Monitor fetal growth and well being There is little point in ultrasound at less than 2w
intervals Timely delivery
Must weigh up the risks of induced delivery against the risk of remaining in utero
Umbilical Artery Doppler Study
Upper panel represents peak (systolic) and trough (diastolic) flow often expressed as S/D ratio
Lower panel is constant flow through a uterine vein
UA Doppler reflects downstream placental resistance
Is the 1st change to occur with placental disease
Abnormal UA Doppler Flows
When flow ceases in the diastolic phase (AEDF) the S/D ratio is very high (∞)
Flow may even reverse in the diastolic phase (RDF) as shown opposite
Uterine Artery Dopplers…
Are of limited use when…▪ The fetus is very premature (<30 weeks)▪ Pregnancy is prolonged (>40 weeks)▪ It is a low risk pregnancy
▪ 5% will be high but normal
▪ Are useful in High Risk Pregnancies▪ May be used to prolong pregnancy with
immature fetus and apparent IUGR▪ Have a high negative predictive value for fetal
death▪ Will change 4 – 7 days before other
changes in fetal wellbeing e.g. Biophysical Profile
Other Pregnancy Doppler Studies
Fetal Middle Cerebral Artery Resistance falls as brain-sparing IUGR begins Strong correlation with fetal HB Of particular use in monitoring intrauterine
haemolysis
Fetal Ductus Venosus Resistance rises as the placenta deteriorates
Maternal Uterine Arteries Increased resistance with bilateral notching at
12 – 24w predicts early (but not late) onset pre eclampsia with ≈ 60% sensitivity
Fetal Biophysical Profile
Ultrasound for… Fetal Breathing Fetal Movements Fetal Tone Amniotic Fluid Volume
Non Stress CTG Looking at fetal heart short term variability and
accelerations Assigns a score of 0,1,2 to each of
these five measures as with the Apgar Score
Scores ≤ 6 are abnormal