The most common definition of fetal growth restriction 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 intrauterine growth restriction (IUGR).
Are there different types of Fetal Growth Restriction?
There are basically two different types of fetal growth restriction:
- Symmetric or primary growth restriction is characterized by all internal organs being reduced in size. Symmetric growth restriction accounts for 20% to 25% of all cases of growth restriction.
- Asymmetric or secondary growth restriction 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 Fetal Growth Restriction?
The following conditions may increase the risk for developing fetal growth restriction:
- Maternal weight of fewer 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 pregnancies
- Gestational diabetes in the mother
- Low levels of amniotic fluid (oligohydramnios)
How is Fetal Growth Restriction diagnosed?
One of the most important aspects of diagnosing fetal growth restriction is ensuring accurate pregnancy dating. Gestational age can be calculated by using the first day of your last menstrual period (LMP) and early ultrasound measurements.
Once gestational age has been established, the following methods can be used to diagnose fetal growth restriction:
- The fundal height that does not coincide with gestational age
- Measurements calculated in ultrasound are smaller than would be expected for the gestational age
- Abnormal findings discovered by a Doppler ultrasound
How is Fetal Growth Restriction treated?
Despite new research, the optimal treatment for fetal growth restriction still has risks. Most likely the type of 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 inducing labor early.
- 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, 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 amniocentesis to evaluate fetal lung maturity.
What are the risks to a baby born with Fetal Growth Restriction?
Babies born with fetal growth restriction have an increased risk for the following:
- Cesarean delivery
- Hypoxia (lack of oxygen when the baby is born)
- Meconium aspiration (This occurs when the baby swallows part of the first bowel movement, which can cause overdistention of the alveoli, a pneumothorax, or 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)
- Motor and neurological disabilities
Compiled from the following sources:
Cunningham, F. Gary, Kenneth J Leveno, Steven L. Bloom, John C. Hauth, Larry Gilstrap III, and Katharine D. Wenstrom ed. Williams Obstetrics 22nd Ed. (New York: McGraw-Hill Publishers), 2005.
Scott, James R., Ronald S. Gibbins, Beth Y. Karlan, Arthur F. Haney ed. Danforth’s Obstetrics and Gynecology 9th Ed. (Philadelphia: Lippincott Williams & Wilkins), 2003.
Olds, Sally B, Marcia L. London, and Patricia Wieland Ladewig, eds. Maternal-Newborn Nursing: A Family-Centered Approach 5th Ed. (New York: Addison-Wesley Nursing), 1996.