Classification Campbell and Thoms (1977) described the use of the sonographically determined head-to-abdomen circumference ratio (HC/AC) to differentiate growth-restricted fetuses. Symmetrical IUGR (type I) Asymetrical IUGR (type II) Combined type
Classification 1.Symmetrical growth restriction 20 % of IUGR Infants proportional decrease in all organs HC/AC ratio is normal Occurs inearly pregnancy : cellular hyperplasia Increase risk for long term neurodevelopmental dysfunction
Classification 2.Asymmetrical growth restriction 75 % of IUGR Infants Increase HC/AC ratio : decrease in abdominal size Brain sparing effects Occurs in late pregnancy : cellular hypertrophy Risk for perinatal hypoxia, neonatal hypoglycemia Good prognosis LOGO
Such somatic growth restriction is proposed to result from preferential shunting of oxygen and nutrients to the brain, which allows normal brain and head growth, so-called brain sparing.
The fetal brain is normally relatively large and the liver relatively small. Accordingly, the ratio of brain weight to liver weight during the last 12 weeks, usually about 3 to 1, may be increased to 5 to 1 or more in severely growth-restricted infants.
Between 18 and 30 weeks, the uterine fundal height in centimeters coincides with weeks of gestation. If the measurement is more than 2 to 3 cm from the expected height or < 1oth percentile from normal curve, inappropriate fetal growth may be suspected
Normal velocimetry pattern with an S/D ratio of <30. The diastolic velocity approaching zero reflects increased placental vascular resistance. During diastole, arterial flow is reversed (negative S/D ratio), which is an ominous sign that may precede fetal demise