1.2 Foetal Surveillance Flashcards
Biophysical profile
Biophysical Profile - assesses acute fetal wellbeing through ultrasound. Takes about 30 mins to avoid sleep as a skew
Biophysical Profile (Score 2 or 0)
Foetal heart rate:
- 2 or more accelerations of 15 bpm for 15 seconds within 30 minutes
- 1 or no acceleration within 30 mins
Foetal muscle tone:
- 1 or more episodes of active extension and return to flexion in 30 mins
- Slow extension and return to partial or no flexion, no movement in 30 mins
Foetal body movements:
- 3 or more in 30 mins
- 2 or less in 30 mins
Foetal breathing movements:
- One or more episodes of FBM of >30 sec in 30 mins
- Absent or no episodes of FBM of >30 sec in 30 mins
Amniotic fluid volume:
- >5cm
- <5cm
Uterine artery doppler studies
- Assesses the effectiveness of placentation and future risk of FGR
- placenta increases uterine blood flow from 60mls/min to 1000mls/min
- Placental insufficiency → unable to meet metabolic needs of foetus → FGR, increased risk of maternal preeclampsia
- Abnormal → high resistance uterine artery doppler study
Umbilical artery doppler studies
- Assesses downstream placental vascular resistance
- Normal → low resistance fetoplacental circulation → maximum blood flow through placenta to deliver oxygen and remove waste → resistance decreases with increasing gestation due to vasodilation. Will show uniform doppler waveform
- Abnormal → increased placental vascular resistance → reduced placental gas and nutrient exchange → FGR
- Abnormal doppler waveform → high systolic and low diastolic ratio
- High systolic and below baseline diastolic = reverse flow
Middle cerebral artery doppler studies
- Assesses growth-restricted foetus and can help show info on acute status of fetus
- With decreasing oxygen availability, the GRF prioritises blood flow to organs, the brain, and heart (a.k.a redistribution) but overtime can cause a reduced abdominal circumference with a normal head (a.k.a asymmetrical growth restriction)
- Normal MCA → high resistance
- Abnormal MCA → low resistance flow and increased diastolic flow → hypoxic
Cerebroplacental ratio
- CPR is the ratio of MCA Doppler Pulsatility Index (PI) to the Umbilical Artery Doppler PI.
- Abnormal → <5th centile
Ductus venosus doppler studies
- Ductus venosus - The blood vessel connecting the portal sinus (abdominal portion of umbilical vein)
- DV waveform reflects fetal heart function (specifically myocardial contractility) especially for early onset FGR
- Abnormal → increased resistance
Fetal growth assessment (biometry)
- A healthy foetus should follow its centile growth trajectory across pregnancy (macrosomia or GR)
- Uses: informs us about future risks
- Limitations: requires accurate EDD, biparietal diameter, head circumference, abdominal circumference, and femur length to derive estimated fetal weight and can be inaccurate
- <5th centile is abnormal. Estimated fetal weight chart is also based on averages.
Measuring amniotic fluid
- Generally done in 3rd trimester
- Woman must be positioned supine
- US Doppler placed over amniotic fluid pocket in a quadrant of the belly
- Vertical callipers measure the depth in centimetres of amniotic fluid (a.k.a deepest vertical pocket)
- Should not cross any foetal body part or umbilical cord (<5 or >25 abnormal)
Intrapartum continuous CTG monitoring (antenatal & intrapartum risk factors)
Antenatal risk factors:
- Abnormal antenatal CTG
- Abnormal Doppler Umbilical Artery velocimetry
- Suspected or confirmed intrauterine growth restriction
- Prolonged pregnancy (>42 weeks)
Intrapartum risk factors:
- Induction of labour with prostaglandin/oxytocin
- Abnormal auscultation or CTG
- Regional anaesthesia
- Abnormal vaginal bleeding in labour
Fetal scalp blood sampling in labour
A small scratch is made on the foetus’ head during labour to test the blood lactate of the baby, which will determine its wellbeing during delivery
<4.1 mmol/L then repeat in 1 hour → >5.8mmol/L or <7 mmol/L requires urgent assisted vaginal birth if possible or Category 1 C-section
Fetal scalp blood sampling in labour - Indications & Contraindications
Indications:
- Bradycardia or complicated tachycardia
- Recurrent decelerations
- Prolonged loss of variability which does not spontaneously correct with fetal stimulation
Contraindications:
- Clear evidence on CTG of serious, sustained fetal compromise
- Maternal infection (Hep B, C, HIV, herpes, suspected intrauterine sepsis)
- Face, brow, or breech presentation
Neonatal cord blood sampling
Determines foetal metabolic condition at the moment of birth and acid-base status. 12-16 mmol/L is associated with encephalopathy. Arterial vessel then vein
Testing can be delayed for a maximum of 90 minutes after birth for accurate results. Keep the umbilical cord clamped and at room temperature. Heparin syringe and cup of ice to preserve samples if needed. Label with baby’s details
Neonatal cord blood sampling - indications, testing, report if
Indications:
- When clinicians are concerned about a potential fetal metabolic abnormality
- Preterm gestation
- Meconium stained liquor
- Assisted emergency birth (i.e., ventouse, instrumental, emergency c-section)
Testing:
- 10-20cm segment of cord double clamped
- Collect from the arterial cord vessels above the bottom clamp prior to collecting routine cord blood samples
OR
- Collect from the detached cord section
Report if:
- pH <7.15
- Base excess >-10
- Lactate >5
- Haemoglobin <140
- Glucose <3
Abnormal fetal growth - macrosomia
A very large foetus (4000-4500g)
Causes: previous maternal history of it, pregnancy weight gain, parity, glucose intolerance, male foetus, and Beckwith-Widemann syndrome, TORCH infection
Risks: postpartum haemorrhage, vaginal lacerations, shoulder dystocia, lower APGAR
Abnormal fetal growth - FGR
Infants with weights lower than expected (<10th centile) or significant drop in centiles
Short-term risks: infant may lack intrauterine reserves to undergo stress of labour
Long-term risks: cardiovascular disease, insulin resistance, obesity
Detecting & managing FGA
Detection:
- fundal height measurement
- estimated foetal weight
- uterine arterial doppler studies
- MCA dopplers
Management:
- foetal surveillance
FGR Identification as per Safer Baby Bundle:
Level 1: No risk factors for FGR identified → standardised serial SFH measurement at each antenatal visit from 24 weeks gestation + US as clinically indicated
Level 2: Risk factor for FGR identified e.g., <20 or >40 y/o, IVF, high or low BMI, pregnancy substance use → FG US at 26-28 weeks and 34-36 weeks, additional US, SFH measurement
Level 3: High risk of early FGH identified e.g., previous early FGR, preeclampsia, previous stillbirth, maternal medical conditions → growth scans every 2-4 weeks from 24 weeks, low dose aspirin 150mg until 36 weeks to reduce risk of preterm preeclampsia
Early & late onset FGR
Early FGR:
- FGR diagnosed <32 weeks gestation (easier to detect, harder to manage)
- 20-30% of FGR is early onset or 0.5-1% of all pregnancies
- Umbilical artery doppler will more likely show abnormalities
Late FGR:
- FGR diagnosed >32 weeks gestation (harder to detect but easier to manage)
- 70-80% FGR are late onset or 5-10% of pregnancies are late FGR
- Uterine artery doppler will more likely show abnormalities
- 2ml IM steroid injection for mum in buttock (before 36 weeks)
- In the event of preterm baby, most likely will not tolerate induction related hyperstimulation (synt, balloon, contractions) → have in mind emergency CAT
Oligohydramnios
Oligohydramnios: less than expected amniotic fluid for gestational age. AFI <5cm
Causes:
- Fetal urinary tract abnormality, PPROM, twin-to-twin transfusion (anaemia), placental insufficiency, post-maturity (>42 weeks), placental abruption
Diagnosis:
- SFH < gestation, reduced DM, abdo palp (fetal parts easily felt)
Management:
- Investigate underlying cause, conservative vaginal delivery, optimise fetal/maternal outcome, maternal bed rest associated with improved liquor volume
Prognosis:
- Often poor if associated with PPROM or fetal abnormality
- Long-term oligo associated w) pulmonary hypoplasia
Polyhydramnios
Polyhydramnios: more than expected amniotic fluid for gestational age. AFI >25cm
Causes:
- Multiple pregnancy (recipient twin), fetal abnormality of GIT, maternal diabetes, Rh Isoimmunisation, idiopathic
Diagnosis:
- US AFI >25cm, SFH > gestational age, fetus easily ballotable, fetal parts hard to palp, maternal symptoms associated w) increased uterine size (resp, GIT, vascular)
Management:
- Reductive amniocentesis, monitor, maternal medication (indomethacin), labour management
Complications:
- Prem labour, placental abruption, fetal abnormality, fetal malposition, macrosomia, cord prolapse (baby not engaged properly), postpartum uterine atony, SROM, breech/moving baby, decreased fetal movement
Prevent stillbirth
Safer Baby Bundle Elements to reduce stillbirth risk after 28 weeks gestation
1. Supporting women to stop smoking in pregnancy
2. Improving screening and surveillance for foetal growth restrictions
3. Improving awareness and management of decreased foetal movement
4. Improving awareness of maternal safe sleeping position
5. Improving decision-making around timing of birth for women with risk factors
