brand logo

Am Fam Physician. 2021;104(5):486-492

Patient information: A handout on this topic is available at https://familydoctor.org/condition/intrauterine-growth-restriction.

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial affiliations.

Fetal growth restriction, previously called intrauterine growth restriction, is a condition in which a fetus does not achieve its full growth potential during pregnancy. Early detection and management of fetal growth restriction are essential because it has significant clinical implications in childhood. It is diagnosed by estimated fetal weight or abdominal circumference below the 10th percentile on formal ultrasonography. Early-onset fetal growth restriction is diagnosed before 32 weeks' gestation and has a higher risk of adverse fetal outcomes. There are no evidence-based measures for preventing fetal growth restriction; however, aspirin used for the prevention of preeclampsia in high-risk pregnancies may reduce the likelihood of developing it. Timing of delivery for pregnancies affected by growth restriction must be adjusted based on the risks of premature birth and ongoing gestation, and it is best determined in consultation with maternal-fetal medicine specialists. Neonates affected by fetal growth restriction are at risk of feeding difficulties, glucose instability, temperature instability, and jaundice. As these children age, they are at risk of abnormal growth patterns, as well as later cardiac, metabolic, neurodevelopmental, reproductive, and psychiatric disorders.

Fetal growth restriction, previously called intrauterine growth restriction, is a condition in which a fetus does not achieve its optimal growth potential. It impacts up to 10% of pregnancies and has significant prenatal and postnatal consequences, including increased risk of perinatal death, neurodevelopmental abnormalities, metabolic syndrome, and cardiovascular disease.14 For fetuses affected by growth restriction, adverse outcomes such as intraventricular hemorrhage, hypoxic ischemic encephalopathy, necrotizing enterocolitis, bronchopulmonary dysplasia, sepsis, and death are more common and severe when estimated fetal weight is below the third percentile, or the 10th percentile if uterine artery flow is abnormal.5

Definition

The term fetal growth restriction is recommended instead of intrauterine growth restriction.1,2,6,7 Fetal growth restriction is a pathologic process and indicates distress preventing the fetus from achieving its ultimate growth potential. The American College of Obstetricians and Gynecologists (ACOG) defines a fetus with fetal growth restriction as having an estimated fetal weight below the 10th percentile for gestational age,1 whereas the Society for Maternal-Fetal Medicine recommends an additional criterion of an abdominal circumference below the 10th percentile for gestational age.7 Severe fetal growth restriction is defined as estimated fetal weight below the third percentile.7 Population-based fetal growth references, such as the Hadlock formula, should be used to determine fetal weight percentiles instead of growth standards based on race and sex.7 Although the Hadlock formula was developed from a small, middle-class population in Texas that was almost exclusively White, it is more accurate at predicting adverse outcomes from fetal growth restriction than more diverse growth standards.810

The term small for gestational age (SGA) applies to newborns whose measured birth weight is less than the 10th percentile for gestational age.1 SGA newborns may have had fetal growth restriction, but may also be constitutionally small, physiologically normal, and have reached their growth potential. Some infants with normal birth weight who experienced growth restriction in utero are at risk of postnatal complications.

Etiology

Fetal, maternal, uteroplacental, and external factors can lead to fetal growth restriction through limited uteroplacental perfusion that limits fetal nutrition (Table 1).1,1114 Placentation and umbilical cord abnormalities are the most common causes of fetal growth restriction.1 Factors associated with fetal growth restriction include multiple gestation, structural anomalies including congenital heart disease and gastroschisis, and genetic abnormalities including trisomies 13, 18, and 21.1113 Maternal nutrition, chronic diseases such as hypertensive disorders and pregestational diabetes mellitus, infections, and external factors such as drug or toxin exposure increase the risk of fetal growth restriction.1113 Although race and ethnicity are identified as risk factors, exposure to structural racism and socioeconomic inequality contributes to fetal growth restriction, not race or ethnicity themselves.14

Fetal
Genetic: gene disorders such as Fanconi anemia and Cornelia de Lange syndrome, trisomies 13, 18, and 21
Major congenital anomalies: anencephaly, congenital heart disease, diaphragmatic hernia, gastroschisis/omphalocele, transesophageal fistula
Maternal
Assisted reproduction
Chronic disease
 Autoimmune: systemic lupus
 Cardiovascular: atherosclerotic cardiovascular disease, congestive heart failure, cyanotic congenital heart disease
 Lung: asthma, chronic obstructive lung disease, cystic fibrosis
 Gastrointestinal: Crohn disease, ulcerative colitis
 Hematologic: severe anemia including sickle cell anemia and sickle cell trait
 Hypertensive disorders: chronic or gestational hypertension, preeclampsia
 Pregestational diabetes
 Renal insufficiency
Environmental or social factors: air pollution, exposure to structural racism and discrimination, high altitude, lower socioeconomic status, malnutrition
Fibroids (limit space for growth)
History of growth restriction or infant is small for gestational age
Infections: cytomegalovirus, HIV, malaria, rubella, syphilis, toxoplasmosis, tuberculosis, varicella
Multiple gestation
Short interpregnancy interval
Toxin/drug exposure: alcohol, antithrombotic drugs other than low-dose aspirin, cocaine, cyclophosphamide, opioids, tobacco, valproic acid (Depakene)
Uteroplacental
Placental abnormalities: abnormal placentation, placental abruption, placental infarcts
Umbilical cord abnormalities: velamentous or marginal cord insertion, single fetal umbilical artery (two-vessel cord)

Screening and Prevention

All pregnant patients should be screened for fetal growth restriction. A detailed medical and obstetric history should be obtained and risk factors, especially modifiable risk factors, should be identified (Table 11,1114 ). Serial growth ultrasonography performed in pregnancies complicated by risk factors including chronic disease in the birthing parent, substance use, or a history of fetal growth restriction allows for earlier diagnosis.1 In the absence of risk factors, fundal height measurements should be obtained at every obstetric visit after 24 weeks' gestation, preferably by the same clinician. If fundal height is more than 3 cm (1.2 in) below gestational age, formal ultrasonography is recommended. Body habitus, multiple gestation, and uterine fibroids limit the effectiveness of fundal height measurements for screening. Formal growth ultrasonography may be considered for these patients.

Already a member/subscriber?  Log In

Subscribe

From $145
  • Immediate, unlimited access to all AFP content
  • More than 130 CME credits/year
  • AAFP app access
  • Print delivery available
Subscribe

Issue Access

$59.95
  • Immediate, unlimited access to this issue's content
  • CME credits
  • AAFP app access
  • Print delivery available

Article Only

$25.95
  • Immediate, unlimited access to just this article
  • CME credits
  • AAFP app access
  • Print delivery available
Purchase Access:  Learn More

Continue Reading

More in AFP

More in Pubmed

Copyright © 2021 by the American Academy of Family Physicians.

This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP.  See permissions for copyright questions and/or permission requests.