fetal growth Flashcards
when is fetal growth assessed
after 24 weeks of gestation
what are the two clinical examination medthods used in assessing fetal growth
- Abdominal palpation of fundal height
- Symphysis-fundal height measurement using a measuring tape
US
at 12 36-38 40 weeks what is the position of the fundus
12 weeks - fundus just above pubic bone
36-38 weeks - fundus usually right up under sternum
40 weeks - fundus drops below 38 week level as presenting part drops down into pelvis
how is fetal growth assessed in US
- Head circumference (and Biparietal diameter)
- Abdominal Circumference
- Femur length
what does small for dates or large dates imply
describe the position of fetal measurements on a gestational population centile chart.
define small for dates/SGA
describes anthropometric variables below the 10th population centile for gestational age
define large for dates/LGA
describes anthropometric variables above the 95th population centile for gestational age
causes for SGA
intrauterine hypoxia, acidaemia, prematurity (often iatrogenic) and neonatal complications
placental insufficiency include low pre-pregnancy weight, substance abuse, autoimmune disease, renal disease, diabetes and chronic hypertension.
what is a growth restricted fetus
A growth restricted fetus is one that has failed to reach its genetic growth potential
RFs for FGR
age
high or low BMI
Previous FGR
Hypertension
Smoking
Alcohol
Substance abuse
Recurrent fetal loss
Previous unexplained SB
Haemoglobinopathies
Domestic Violence
Raised AFP
Antiphospholipid syndrome
Prescription and OTC Drugs
Infection
Collagen vascular disease
High altitude
Placental pathology (praevia, cirumvallata
Renal disease
If a small baby is referred what do u do
- Is the fetus really small (confirm diagnosis)
- Why is the fetus small (establish cause)
- How to monitor pregnancy with a small fetus (make management plan)
- Timing and mode of delivery (weigh up risks and benefits)
how to diagnose small baby
measure using US scan
what is
Normal small Abnormal small Infected small Starved small Wrong small
Normal Small
Constitutionally small, healthy baby
Abnormal Small
Chromosomal abnormalities, syndromes, congenital malformations
Infected Small
Infection during pregnancy (commonly CMV)
Starved Small ‘Placental FGR’ - placental growth restricted due to - poor placentation - smoking - maternal disease affecting placenta - multiple pregnancy etc
Wrong Small
Incorrect Dates or measurements
what does Adequate trans-placental transfer depends on
- Uteroplacental blood flow (from the uterine artery to the placenta
- Villous structure at the interface of maternal and fetal blood
- Fetoplacental blood flow (from the umbilical arteries to the placenta
how to measure successful trophoblast invasion
assessed with a uterine artery Doppler
at 20 weeks gestation
what additional sonographic measures will help differentiate SFD from FGR
- Centile position
- Symmetry
- Liquor volume
- UMA Doppler
- Growth velocity
DD for SGA
healthy small baby
aneuploidy/infection
placental IUGR
how will
1) growth symmetry and velocity
2) amniotic fluid
3) fetal well being
in healthy small baby be
1) normal velocity, symmetrical growth
2) normal
3) normal UMA doppler
how will
1) growth symmetry and velocity
2) amniotic fluid
3) fetal well being
in aneuploidy/infection
1) markedly small, velocity may be reduced, symmetrical (??) growth
2) variable, usually normal or increase
3) normal UMA doppler
how will
1) growth symmetry and velocity
2) amniotic fluid
3) fetal well being
in placental IUGR
1) often asymmetrical velocity may be reduced
2) may be reduced
3) evidence of high resistance UMA flow BPP score decreases
what maternal monitoring is done in SGA babies
1) Assess for any modifiable factors (smoking) bring it up in every clinic
2) Assess for presence of maternal disease
3) Continue monitoring for pre-eclampsia, with blood pressure and urine checks, in regular intervals
what fetal surveillance is done in SGA babies
1) Serial growth measurements (every 2-4 weeks)
2) Fetal wellbeing surveillance Maternal perception of fetal movements Fetal Doppler Amniotic volume measurements Biophysical profile
As resistance increases in the umbilical artery what will u see in UMA
1) decreased end-diastolic velocity
2) absent end-diastolic velocity
3) reversed end-diastolic velocity
what is uterine arteries doppler
- Dopplers illustrate successful remodelling and conversion into high flow, low pressure vessels
- Useful for screening, where notching identifies high risk patients
- NOT USEFUL FOR SURVEILLANCE- performed as a screening test at 20 weeks
what i UMA umbilical artery
- End-diastolic flow velocity (continuous, absent, reversed) reflects increases in placental resistance
- Essential in surveillance of the growth restricted fetus
USEFUL FOR SURVEILLANCE
what is MCA
- Represents downstream resistance in cerebral microcirculation
- MCA resistance is normally high throughout gestation, with increasing flow in the third trimester
- Increased diastolic flow signifies onset of circulatory changes in response to placental disease
- Also useful at later gestation, where placental changes in FGR may be functional rather than structural and MCA compensatory flow may be present with near normal UMA Doppler
USEFUL FOR SURVEILLANCE
what is venous dopplers
- Candidate vessels include IVC, UVC, and hepatic veins, but evidence still poor.
- The ductus venosus is probably the vein of choice
- Waveform deterioration precedes, and strongly predicts, changes in BPS requiring delivery
USEFUL FOR SURVEILLANCE
when to deliver baby according to AREDF
- When umbilical artery Doppler is normal, delay delivery until at least 37 weeks (in the presence of satisfactory additional assessment)
- With AREDF consider delivery if gestation >34/40 even in the presence of normal additional assessment
- With AREDF, deliver before 34/40 if CTG abnormal, BPP abnormal, or other Doppler parameters are abnormal (MCA, umbilical vein)
- Mode of delivery will depend on gestation, presentation, fetal condition and maternal factors
risks of a fetal growth restricted baby
- Odds ratio for perinatal death 2.5
- Increased need for resuscitation
- Hypothermia & Hypoglycaemia
- RDS & NEC
- Neurodevelopmental disability
- Cerebral palsy
- Adult disease
what are the other causes for an increased symphysis fundal height in a singleton pregnancy
- Uterine fibroids
- Pelvic mass pushing up the uterus
- Polyhydramnios
- Maternal obesity
maternal factors that cause large for dates baby
- Diabetes
- Obesity
- Increased maternal age
- Multiparity
- Large stature
possible causes of a large baby
- Constitutional
- Male gender
- Postmaturity
- Genetic disorders (Beckwith Wiedeman)
maternal Risks of having a macrosomic baby
- Prolonged labour
- Operative delivery
- Postpartum haemorrhage
- Genital tract trauma
fetal RFs of having a macrsomic baby
- Birth injury
- Perinatal asphyxia from difficult delivery
- Shoulder dystocia/Erb’s palsy
- Hypoglycaemia
- Childhood obesity
- Metabolic syndrome
what to do w a chunky baby
- Exclude maternal diabetes
- In the absence of polyhydramnios, treat pregnancy as normal
- There is NO benefit of induction of labour or Caesarean section in the absence of maternal diabetes
If maternal diabetes is present in addition to macrosomia, offer Caesarean section - Early recourse to intervention where there is delay in labour
- Anticipate shoulder dystocia
- Monitor for hypoglycaemia in the neonatal period
what can reduced fetal movements mean
fetal distress, as a method of fetal compensation to reduce oxygen consumption as a response to chronic hypoxia in utero. This is concerning, as it reflects risk of stillbirth and fetal growth restriction.
when is the first onset of recognised fetal movements
quickening - 18-20 weeks and icnrease until 32 weeks gestation where the movements plateau
multiparous women from 16-18 weeks
RFs/reasons for reduced fetal movements
Posture
- There can be positional changes in fetal movement awareness, generally being more prominent during lying down and less when sitting and standing
Distraction
- Awareness of fetal movements can be distractable, and if a woman is busy or concentrating on something else, these can be less prominent
Placental position
- Patient with anterior placentas prior to 28 weeks gestation may have lesser awareness of fetal movements
Medication
- Both alcohol and sedative medications like opiates or benzodiazepines can temporarily cause reduced fetal movements
Fetal position
- Anterior fetal position means movements are less noticeable
Body habitus
- Obese patients are less likely to feel prominent fetal movements
Amniotic fluid volume
- Both oligohydramnios and polyhydramnios can cause reduction in fetal movements
Fetal size
- Up to 29% of women presenting with RFM have a SGA fetus
if RFM past 28 weeks gestation
1) handheld doppler - confirm fetal heartbeat
1a) if no fetal heartbeat - immediate US
2) if fetal heartbeat present - CTG should be used for at least 20 minutes to monitor fetal heart rate which can assist in excluding fetal compromise.
If concern remains, despite normal CTG, urgent (within 24 hours) ultrasound can be used.
Ultrasound assessment should
- abdominal circumference or
- estimated fetal weight (to exclude SGA),
- and amniotic fluid volume measurement
if RFM between 24-28w, below 24w
- If between 24 and 28 weeks gestation, a handheld Doppler should be used to confirm presence of fetal heartbeat.
- If below 24 weeks gestation, and fetal movements have previously been felt, a handheld Doppler should be used.
- If fetal movements have not yet been felt by 24 weeks, onward referral should be made to a maternal fetal medicine unit.
At which week should you refer to an obstetrician for lack of fetal movements?
24 weeks refer to maternal fetal medicine unit
