fetal growth restriction (FGR / SGA / IUGR)

see also:

• pregnancy
• decreased fetal movements (DFM or RFM)
• Obstetrics
• RANZCOG guidelines
• WH guideline - intranet only

• Small for Gestation Age (SGA) refers to a fetus with an estimated weight (EFW) and/or abdominal circumference (AC) less than the 10th centile.
• fetuses who are SGA may be either:
  • constitutionally small (50-70% of cases of SGA), or,
  • small due to fetal growth restriction (FGR) “failed to achieve its biological growth potential”
• some FGR fetuses are above the 10th centile threshold for EFW /AC
• distinguishing between a constitutionally small fetus and a growth restricted fetus in the antenatal period is difficult although those with FGR may have:
  • evidence of fetal compromise (abnormal Doppler and liquor volume)
  • reducing growth trajectory
  • severe SGA (<3rd centile) (these are more likely to be due to FGR than constitutionally small fetus
• 8-fold increase in perinatal mortality for infants with a birthweight <10th centile, rising to approximately 20-fold increase for infants with a birthweight ≤ 3rd centile
• SGA babies account for a third of non-anomalous stillbirth / FDIU
• Infants born SGA due to FGR were shown to have higher rates of neurodevelopmental delay, poor school performance and childhood and adult metabolic disease
• Recognition of SGA on ultrasound is associated with a significant improvement in perinatal mortality, as it allows appropriate surveillance and timely intervention by elective birth

• medical conditions:
  • preeclampsia, essential hypertension, cyanotic heart disease, chronic pulmonary disease, chronic kidney disease, pre- gestational diabetes mellitus, thyrotoxicosis, severe chronic anaemia, sickle cell disease, SLE, antiphospholipid syndrome, inflammatory bowel disease, bariatric surgery, pre- pregnancy pelvic radiation
• teratogens
  • warfarin, anticonvulsants, methotrexate, immunosuppressive agents, antineoplastic agents;
• toxins
  • cigarettes, recreational drugs, alcohol;
• Assisted reproductive technology
• Low pre- pregnancy weight/ poor gestational weight gain
• BMI >35
• Maternal age <20 or >35

• chromosomal disorder
• congenital infection - CMV, toxoplasmosis (consider syphilis, malaria in patient with risk factors)
• structural abnormalities
• multiple pregnancy

• see placental insufficiency
• ischaemic placental disease - preeclampsia, recurrent placental abruption
• cord and placental abnormalities- two vessel cord, velamentous/ marginal cord insertion, circumvallate placenta, placental hemangioma
• confined placental mosaicism- chromosomal mosaicism (usually a trisomy) in the placenta but not in the fetus.

• manage risk factors prior to 20 weeks gestation
  • consider low dose aspirin 100-150mg/d (starting between 12-16wks and continued until 36wks) in certain high risk patients
  • cease smoking
• screening to detect SGA
  • first trimester ultrasound for dating and nuchal translucency;
  • First and second trimester screening tests for aneuploidy maybe useful tests of placental function.
    • If two screening test results are abnormal, health care providers should be aware that the fetus is at increased risk of preterm intrauterine growth restriction and associated stillbirth
  • fundal height assessments > 2cm less than expected
  • ultrasound biometric tests at 18wks, 28wks and 36wks
  • uterine artery Doppler at 19 to 23 weeks if biochemical markers are abnormal
  • ultrasound examination for estimated fetal weight and amniotic fluid volume should be considered after 26 weeks if the symphysis-fundal height measurement in centimetres deviates by 3 or more from the gestational age in weeks or there is a plateau in symphysis-fundal height
• Mx of SGA:
  • referral to fetal medicine specialty clinic
  • morphology ultrasound to exclude fetal anomalies, and fetal aneuploidy
  • TORCH serology (and syphilis and malaria as appropriate) and consider amniocentesis if suspect fetal infection
  • if < 32wks with SGA, consider amniocentesis for fetal karyotype
  • monitor for pre-eclampsia which has a higher risk in these patients (60% with early FGR 15% in late FGR)
  • daily monitoring of fetal movements
  • consider:
    • umbilical artery (UA) Doppler
      • abnormal Doppler wave forms may be found in association with early onset FGR.
    • middle cerebral artery (MCA) Doppler:
      • a low MCA PI (<5th centile) indicates fetal blood flow redistribution. This is known as the “brain sparing effect” and is a normal physiological response of the growth restricted fetus.
    • Ductus venosus (DV) Doppler
    • Amniotic Fluid Index (AFI)
    • Biophysical profile (BPP)
  • antenatal corticosteroids should be considered in all cases with FGR ≤36 weeks gestation and where the decision has been made for elective birth as this is proven to reduce perinatal morbidity and mortality in these cases
    • steroids may be considered up to 38 weeks of gestational age in cases of elective Caesarean Section.
  • timing and mode of birth to be considered