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Fetal growth restriction

Definition

Fetal growth restriction (FGR) is defined by the finding of growth below the genetically expected potential

The most sensitive and clinically practicable single physical parameter in the diagnosis of FGR is a measurement of the fetal abdominal circumference (AC) below the 5th percentile of the normal range for gestation  

The differential diagnosis includes:

Wrong dates: the fetus is anatomically normal, the measurements are symmetrically small, the amniotic fluid, fetal activity and placental Doppler are all normal. A repeat scan in two weeks shows normal growth velocity

Normal small: the fetus is anatomically normal, the measurements are symmetrically small, the amniotic fluid, fetal activity and placental Doppler are all normal. A repeat scan in two weeks shows a decrease in growth velocity

Starving small: the fetus is anatomically normal, the measurements are asymmetrically small with the abdomen and femur being more affected than the head, the amniotic fluid volume and fetal activity are reduced, the pulsatility index in the uterine and/or umbilical arteries is increased and in the middle cerebral artery is reduced, the fetal heart rate pattern may be and/or ductus venosus flow may be abnormal. A repeat scan in two weeks may show a marked decrease in growth velocity and deterioration in the fetal condition

Abnormal small: the fetus may have abnormalities suggestive of aneuploidies, genetic syndromes or congenital infection. The measurements may be symmetrically small or there may asymmetrical decrease in the head or limbs. The amniotic fluid volume and fetal activity may be decreased, increased or normal. The fetal heart rate pattern and Doppler indices in the placental and fetal circulations may be normal or abnormal. A repeat scan in two weeks may show a decrease in growth velocity

The differential diagnosis and clinical progression provides the rationale for the integrated use of surveillance modalities