Foetal Growth Flashcards
How is foetal growth assessed?
Symphysis fundal height measurement (30-40% sensitivity)
USS assessment is the most accurate way of doing this.
1. Biparietal diameter and head circumference
2. Abdominal circumference – most important measurement for foetal growth
3. Femur length
What can influence uterine measurement of growth and cause them to be inaccurate?
Uterine measurement of growth can be wrong because: • Wrong dates • Oligohydramnios/Polyhydramnios • IUGR/Macrosomia • Presenting part deep in pelvis • Abnormal lie • Multiple pregnancies • Fibroids
Is a baby that is SGA or LGA always a problem?
Small for dates or large for dates do not imply presence of pathology they are simply a measurement of where that baby comes compared to the rest of the population.
What is the definition of SGA and what are the complications/risks as a result of this diagnosis?
Definition: a growth restricted foetus is one that fails to reach its genetic potential.
Low birth weight = <2.5kg
SGA = estimated foetal weight <10th centile.
Higher risk of perinatal morbidity and mortality. Primarily this is due to foetal growth restriction from: hypoxia, acidaemia, prematurity and neonatal complications.
What are the risk factors for SGA?
Advancing age (>35) BMI < 20 Smoking, alcohol and substance misuse (especially cocaine) Domestic violence High altitude Previous FGR Previous foetal loss Maternal/paternal SGA IVF singleton Raised AFP or Low PAPP-A Infection Placental pathology including previous or current PET Maternal disease: haemoglobinopathies, poor diet, renal impairment and vascular disease Daily vigorous exercise
What are the causes of SGA
Foetal
Chromosomal abnormality, congenital malformations, multiple pregnancy and congenital infections i.e. CMV, rubella and toxoplasmosis
Maternal
Chronic maternal disease, substance misuse, smoking, autoimmune disease (antiphospholipid syndrome), poor nutrition and low socio-economic status
Placental
Pre-eclampsia, placenta accreta, infarction, abruption and placental praevia
How should you assess and investigate a potentially SGA foetus?
Is this foetus really small? – confirm dates, asses growth by USS and review measurements. Could this be normal – constitutionally small baby actually healthy (growth charts account for maternal weight, height and ethnicity).
SFH important first screen
USS of foetus
• Symmetrical? – symmetrically small likely constitutional small or chromosomal abnormality, asymmetrically small more likely placental insufficiency (foetus directs blood to brain and heart which continue to grow)
• Liquor volume – will be reduced if FGR as heart shunts away from kidneys
• Assess growth on population centile – has it fallen or stalled? (only assess every 2 weeks)
After confirming that a baby is SGA how should you investigate for pathlogy?
Assess placental formation with uterine maternal artery doppler – screen for high risk patients and assessment of high flow, low resistance system (only useful 20-24weeks).
Assess foetal health
• Umbilical artery doppler – look at end diastolic flow for surveillance of foetal status.
• Middle cerebral artery doppler – also good for surveillance especially in later gestation when UMA may be normal
• Ductus Venosus Doppler (new) – probably useful for surveillance
• CTG
If looking for a cause:
Detailed anomaly scan
Karyotyping
Screening for infections – CMV, toxoplasmosis, syphilis and malaria
How are high risk SGA foetuses monitored?
Surveillance on growth pathway with scans every 2-4 weeks and foetal doppler for high risk babies (maternal history, signs of PET, low SFH and foetal movements)
How should SGA babies be managed depending on Doppler results?
Umbilical artery doppler normal – delay delivery until at least 37 weeks
With absent or reversed end diastolic flow consider delivery if >34 weeks
With absent or reversed end diastolic flow deliver <34 if CTG abnormal, USS abnormal or other doppler parameters are abnormal
Remember to give steroids if possible – betamethasone 12mg IM
Mode of delivery dependant on gestation, presentation, foetal and maternal condition
What are the common foetal complications during and following delivery of a growth restricted baby?
During Delivery
Increased risk perinatal death and asphyxia
Meconium aspiration and emergency CS
Following Delivery
Increased need for resuscitation
Hypocalcaemia and hypoglycaemia
Respiratory distress syndrome and necrotising enterocolitis
Neurodevelopmental disability
Cerebral palsy
Long term problems – not achieving adult height, learning deficits etc.
What is the definition for a LGA baby?
Foetuses above 95th centile.
What can cause a baby to be LGA?
Maternal Diabetes Obesity Increased maternal age Multiparity Large stature
Foetal Constitutional Male gender Post maturity Genetic conditions (Bechwith Wiedeman)
What are the complications of a LGA baby?
Maternal Prolonged labour Operative delivery PPH Genital tract trauma
Foetal Birth injury Perinatal asphyxia Shoulder dystocia and resulting erb’s palsy Hypoglycaemia Childhood Obesity Metabolic syndrome
How should LGA babies be managed?
Is the foetus really large – establish correct dates. Symphysis fundal height not reliable for LGA as there are many other reasons why this may be raised so USS very important.
Exclude maternal diabetes
In the absence of polyhydramnios and maternal diabetes then treat pregnancy as normal
Early recourse to intervention where there is delay in Labour
Anticipate shoulder dystocia and monitor for hypoglycaemia post delivery
No benefit of IOL or C section in the absence of maternal disease
If Maternal diabetes and macrosomic baby (>4.5kg), then offer C section
