Intrauterine growth restriction

Last updated: June 6, 2023

Summarytoggle arrow icon

Intrauterine growth restriction (IUGR) is defined as lower than normal fetal growth characterized by an estimated fetal weight below the 10th percentile for a given gestational age. There are two types of IUGR: asymmetrical and symmetrical. Asymmetrical IUGR is caused by extrinsic influences (most commonly placental insufficiency) that affect the fetus in the later stages of gestation and symmetrical IUGR is caused by intrinsic influences (e.g., early intrauterine infections, aneuploidy) that affect the fetus in the early stages of gestation. IUGR is diagnosed with serial ultrasound, which demonstrates decreased fetal growth and oligohydramnios. Typical manifestations of asymmetrical IUGR are a normal fetal head size with a disproportionately small body and limbs, while symmetrical IUGR typically manifests with a global growth restriction of the head and body and can lead to an increased risk of neurologic sequelae. Treatment should address the underlying cause. Regular nonstress test (NST), contraction stress test (CST), and biophysical profile (BPP) are recommended to closely monitor fetal status and placental development. Labor induction or cesarean delivery should be considered if the infant is close to term or if there are signs of nonreassuring fetal status.

Epidemiologytoggle arrow icon

Epidemiological data refers to the US, unless otherwise specified.

Etiologytoggle arrow icon

Maternal causes

Uteroplacental causes

Fetal factors

Asymmetrical IUGR is the most common manifestation of IUGR (∼ 70%), has a late onset, and is usually due to maternal systemic disease (e.g., hypertension) that results in placental insufficiency. Symmetrical IUGR is less common (∼ 30%) and is usually due to a genetic disorder (e.g., aneuploidy), congenital heart disease, or early intrauterine TORCH infection that affects the fetus early in gestation.


Pathophysiologytoggle arrow icon

Recent studies show that symmetry of body proportions alone can not reliably indicate intrinsic or extrinsic etiology, therefore the terms “symmetrical” and “asymmetrical” for IUGR are advised not to be used anymore. For exam purposes and because it is still used in some resources, we are covering the division. [5]

Asymmetrical IUGR

Caused by extrinsic factors, which affect the fetus in the later stages of gestation (i.e., third trimester).

Symmetrical IUGR

Caused by intrinsic factors (e.g., genetic abnormalities, infections), which affect the fetus in the early stages of gestation.


Clinical featurestoggle arrow icon

Fetal signs

  • Small for gestational age (or with a birth weight below 10th percentile) [3]
  • Decreased or absent fetal movements [8]
  • Asymmetrical IUGR: disproportionate growth restriction
    • The dimensions of the head are normal while the body and limbs are thin and small.
  • Symmetrical IUGR: global growth restriction
    • The entire body is proportionally small.
    • The circumference of the head is proportional to the rest of the fetal body.
    • ↑ Risk of neurologic sequelae [9]

Maternal signs

Diagnosticstoggle arrow icon

Differential diagnosestoggle arrow icon

Constitutionally small fetus

  • Definition: estimated fetal weight < 10th percentile without an identified underlying condition
  • Predisposing factors [13]
    • Low maternal height
    • Low maternal weight before/in early pregnancy
    • Asian descent [14]
    • Parity
    • Fetal female sex
  • Diagnosis
  • Prognosis: constitutionally small fetuses are not at increased risk for adverse perinatal outcomes

The differential diagnoses listed here are not exhaustive.

Treatmenttoggle arrow icon

Complicationstoggle arrow icon

We list the most important complications. The selection is not exhaustive.

Referencestoggle arrow icon

  1. Placental Calcification. Updated: January 1, 2017. Accessed: October 27, 2017.
  2. Biophysical Profile Score (BPS or BPP). Updated: January 1, 2016. Accessed: October 27, 2017.
  3. Beckmann CRB. Obstetrics and Gynecology. Lippincott Williams & Wilkins ; 2010
  4. Swanson RW, Tallia AF, Scherger JE, Dickey N. Swanson's Family Medicine Review. Elsevier Health Sciences ; 2009
  5. Leveno K, Bloom S, Casey B, et al.. Williams Obstetrics. McGraw-Hill Education Ltd ; 2018
  6. Resnik R. Fetal Growth Restriction: Evaluation and Management. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: October 12, 2017. Accessed: April 27, 2017.
  7. Sharma D, Shastri S, Sharma P. Intrauterine Growth Restriction: Antenatal and Postnatal Aspects. Clin Med Insights Pediatr. 2016; 10: p.67–83.doi: 10.4137/cmped.s40070 . | Open in Read by QxMD
  8. Gardosi J. New Definition of Small for Gestational Age Based on Fetal Growth Potential. Hormone Research in Paediatrics. 2006; 65 (Suppl. 3): p.15-18.doi: 10.1159/000091501 . | Open in Read by QxMD
  9. Lee AC, Katz J, Blencowe H, et al. National and regional estimates of term and preterm babies born small for gestational age in 138 low-income and middle-income countries in 2010. The Lancet Global Health. 2013; 1 (1): p.e26-e36.doi: 10.1016/s2214-109x(13)70006-8 . | Open in Read by QxMD
  10. Gardosi J, Francis A, Turner S, Williams M. Customized growth charts: rationale, validation and clinical benefits. Am J Obstet Gynecol. 2018; 218 (2): p.S609-S618.doi: 10.1016/j.ajog.2017.12.011 . | Open in Read by QxMD
  11. Harkness UF, Mari G. Diagnosis and management of intrauterine growth restriction. Clin Perinatol. 2004; 31 (4): p.743-764.doi: 10.1016/j.clp.2004.06.006 . | Open in Read by QxMD
  12. Salomon LJ, Alfirevic Z, Da Silva Costa F, et al. ISUOG Practice Guidelines: ultrasound assessment of fetal biometry and growth. Ultrasound in Obstetrics & Gynecology. 2019; 53 (6): p.715-723.doi: 10.1002/uog.20272 . | Open in Read by QxMD
  13. Ross M.G.. Fetal growth restriction. In: Smith C.V., Fetal growth restriction. New York, NY: WebMD. Updated: July 25, 2018. Accessed: May 2, 2019.
  14. Baschat DAA. Fetal responses to placental insufficiency: an update. BJOG. 2004; 111 (10): p.1031-1041.doi: 10.1111/j.1471-0528.2004.00273.x . | Open in Read by QxMD
  15. Intrauterine Growth Retardation. . Accessed: April 1, 2019.
  16. Belizán JM, Villar J, Nardin JC, Malamud J, De Vicurna LS. Diagnosis of intrauterine growth retardation by a simple clinical method: measurement of uterine height.. Am J Obstet Gynecol. 1978; 131 (6): p.643-6.doi: 10.1016/0002-9378(78)90824-4 . | Open in Read by QxMD
  17. Foley MR, Lockwood CJ, Gersh BJ, Eckler K. Maternal Cardiovascular and Hemodynamic Adaptations to Pregnancy. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: November 11, 2015. Accessed: April 27, 2017.
  18. Placental insufficiency. Updated: April 10, 2016. Accessed: April 27, 2017.
  19. Dutta DC, Konar H. Textbook of Obstetrics. Jaypee Brothers Medical Publishers ; 2015
  20. Jacob A. A Comprehensive Textbook of Midwifery and Gynecological Nursing, Third Edition. JP Medical Ltd ; 2012
  21. Oligohydramnios. Updated: January 1, 2014. Accessed: October 27, 2017.

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