The IUGR medical abbreviation stands for intrauterine growth restriction, a term used in pregnancy when a fetus is growing more slowly than expected and is estimated to be smaller than most babies at the same stage. Many obstetric teams now prefer the term fetal growth restriction, or FGR, which means the same thing.
You may see IUGR on prenatal ultrasound reports, obstetric notes, labor and delivery handoffs, and newborn records. An older expansion, intrauterine growth retardation, still turns up in old charts but has been replaced because of the wording. This page explains how the label is defined, what the report numbers mean, and how it differs from similar terms.
At a glance
Stands for
Intrauterine growth restrictionAlso written
FGR, fetal growth restrictionOlder expansion
Intrauterine growth retardation, no longer usedUsual definition
Estimated fetal weight or belly size below the 10th percentileUsed in
Obstetrics, maternal fetal medicine, ultrasound, neonatologyDo not confuse with
SGA, small for gestational age, a label for the baby after birth
What the IUGR medical abbreviation means in pregnancy
Ultrasound estimates the size of a fetus from measurements of the head, belly and thigh bone. These are combined into an estimated fetal weight, compared with charts for the same gestational age. When the estimate, or the belly measurement, falls below the 10th percentile, many teams use the term IUGR or FGR. Very low percentiles or abnormal blood flow studies point to more significant restriction.
Not every small fetus has a problem. Some are simply small, like small parents. The label prompts closer monitoring so the team can tell a healthy small baby from one whose growth is being held back.
Common reasons behind growth restriction
The most frequent cause is reduced function of the placenta, which supplies oxygen and nutrients. Maternal factors include high blood pressure, preeclampsia, diabetes with blood vessel changes, smoking and some infections. Fetal factors include certain genetic conditions and twin pregnancies. Teams often describe the pattern as symmetric, where all measurements are small, or asymmetric, where the belly is small but the head is relatively spared, which often points to the placenta.
Reading an IUGR ultrasound line
| Term | Meaning |
|---|---|
| 32w | 32 weeks of pregnancy |
| EFW | Estimated fetal weight |
| 6th percentile | Smaller than 94 of 100 fetuses at that stage |
| AC | Abdominal circumference, the belly measurement |
| UA Doppler | Blood flow study of the umbilical artery, not urinalysis here |
| NST | Nonstress test, a check of the fetal heart rate pattern |
Handoff on a prenatal unit: "G2P1 at 34 weeks, IUGR, AEDF on UA Doppler, BMZ given." The team is noting absent end diastolic flow in the umbilical artery, a sign of strained placental flow, and that steroid shots were given to help the baby's lungs in case of early delivery.
Points to raise with the obstetric team
Helpful questions include how the growth was measured, what the blood flow studies show, how often scans and heart rate checks are planned, and what findings would change the timing of delivery. Some families also ask whether a specialist in maternal fetal medicine will be involved.
This explanation is general. Your obstetrician, midwife or maternal fetal medicine specialist can tell you what a growth finding means in your pregnancy.
Frequently asked questions
What does IUGR mean in pregnancy?
IUGR means intrauterine growth restriction. The fetus is growing slower than expected and is estimated to be below the 10th percentile for size at that stage of pregnancy.
Is IUGR the same as FGR?
Yes. Fetal growth restriction is the newer preferred name for the same finding, and both appear in records.
What is the difference between IUGR and SGA?
IUGR describes growth before birth, based on ultrasound. SGA describes a newborn whose birth weight is small for its gestational age.
Does IUGR always mean a problem with the baby?
Not always. Some small fetuses are healthy and constitutionally small. Monitoring with ultrasound and heart rate tests helps the team tell the difference.