The most common definition of intrauterine growth restriction (IUGR) is a fetal weight that is below the 10th percentile for gestational age as determined through an ultrasound. This can also be called small-for gestational age (SGA) or fetal growth restriction.
Are there different types of IUGR?
There are basically two different types of IUGR:
- Symmetric or primary IUGR is characterized by all internal organs being reduced in size. Symmetric IUGR accounts for 20% to 25% of all cases of IUGR.
- Asymmetric or secondary IUGR is characterized by the head and brain being normal in size, but the abdomen is smaller. Typically this is not evident until the third trimester.
What are the risk factors for developing IUGR?
Pregnancies that have any of the following conditions may be at a greater risk for developing IUGR:
- Maternal weight of less than 100 pounds
- Poor nutrition during pregnancy
- Birth defects or chromosomal abnormalities
- Use of drugs, cigarettes, and/or alcohol
- Pregnancy induced hypertension (PIH)
- Placental abnormalities
- Umbilical cord abnormalities
- Multiple pregnancy
- Gestational diabetes in the mother
- Low levels of amniotic fluid or oligohydramnios
How is IUGR diagnosed?
One of the most important things when diagnosing IUGR is to ensure accurate dating of the pregnancy. Gestational age can be calculated by using the first day of your last menstrual period (LMP) and also by early ultrasound calculations.
Once gestational age has been established, the following methods can be used to diagnose IUGR:
- Fundal height that does not coincide with gestational age
- Measurements calculated in an ultrasound are smaller than would be expected for the gestational age
- Abnormal findings discovered by a Doppler ultrasound
How is IUGR treated?
Despite new research the optimal treatment for IUGR remains problematic. Most likely the treatment will depend on how far along you are in your pregnancy.
- If gestational age is 34 weeks or greater, health care providers may recommend being induced for an early delivery.
- If gestational age is less than 34 weeks, health care providers will continue monitoring until 34 weeks or beyond. Fetal well-being and the amount of amniotic fluid will be monitored during this time. If either of these becomes a concern, then immediate delivery may be recommended. Depending on your health care provider, you will likely have appointments every 2 to 6 weeks until you deliver. If delivery is suggested prior to 34 weeks, your health care provider may perform an amniocentesis to help evaluate fetal lung maturity.
What are the risks to a baby born with IUGR?
- Increased risk for cesarean delivery
- Increased risk for hypoxia (lack of oxygen when the baby is born)
- Increased risk for meconium aspiration, which is when the baby swallows part of the first bowel movement. This can cause the alveoli to be over distended, a pneumothorax to occur, and/or the baby can develop bacterial pneumonia.
- Hypoglycemia (low blood sugar)
- Polycythemia (increased number of red blood cells)
- Hyperviscosity (decreased blood flow due to an increased number of red blood cells)
- Increased risk for motor and neurological disabilities
Compiled using information from the following sources:
Williams Obstetrics Twenty-Second Ed. Cunningham, F. Gary, et al, Ch. 12.
Danforths Obstetrics and Gynecology Ninth Ed. Scott, James R., et al, Ch. 38.
Maternal-Newborn Nursing: A Family-Centered Approach Fifth Ed. Olds, Sally B., et al, 1996.