IUGR & IUFD
Definitions
- Intrauterine growth restriction (IUGR): When the estimated fetal weight falls below the 10th percentile for gestational age. “always pathological”
- Small for gestational age (SGA): newborns who are smaller in size than normal for the gestational age or (weight below 2 SD below the mean). “Pathological or non-pathological”
Symmetrical vs Asymmetrical IUGR
| Symmetrical | Asymmetrical |
|---|---|
| 20-30% of IUGR | 70-80% of IUGR |
| The fetus is proportionally small | Abdominal growth lags behind head circumference. |
| Thought to result from an intrinsic (i.e. genetic) or first-trimester early insult (e.g. infection) that interferes with early fetal cellular hyperplasia, producing uniformly reduced growth | Late pregnancy insult Thought to result from adaptation to a hostile environment by redistributing blood flow in favour of vital organs (e.g. brain, heart) at the expense of nonvital fetal organs (e.g. liver, kidneys) |
| Causes: chemical exposure, infection, or chromosomal disorders, congenital malformation | Placental insufficiency (Main pathology) |
| Head circumference, length, weight and abdomen circumference are decreased proportionally | Head circumference is spared relative to decreased weight, length, and/or abdominal circumference |