Intrauterine Growth Restriction (IUGR)
IUGR refers to a condition in which a fetus does not achieve its geneticallypredicted growth potential, resulting in an estimated fetal weight below the 10th percentile for gestational age.
1. Types of IUGR
1.1 Symmetrical (Earlyonset) IUGR
Occurs before the end of the second trimester, often due to genetic or chromosomal anomalies, maternal infections (e.g., TORCH), or early maternal malnutrition. The fetus shows proportionally reduced head, abdomen, and femur measurements.
1.2 Asymmetrical (Lateonset) IUGR
Develops after the midsecond trimester, usually because of placental insufficiency. Head circumference may be relatively preserved while abdominal circumference lags, creating a headsparing pattern.
2. Etiology
The causes are multifactorial and can be grouped into four major categories:
- Maternal factors: chronic hypertension, preeclampsia, autoimmune disease, smoking, alcohol, drug abuse, severe anemia, malnutrition.
- Uteroplacental factors: placental infarction, thrombosis, abnormal implantation, maternal vascular disease.
- Fetal factors: chromosomal abnormalities (trisomy 21, 18), congenital infections, multiple gestation, structural anomalies.
- Environmental factors: high altitude, chronic hypoxia, exposure to toxins.
3. Pathophysiology
Reduced perfusion of the placenta leads to chronic hypoxia and nutrient deprivation. The fetus adapts by redistributing blood flow to essential organs (brain, heart) at the expense of peripheral tissues, which manifests as the classic asymmetrical growth pattern.
4. Clinical Presentation & Diagnosis
4.1 Antenatal Screening
- Fundal height discrepancy: Measurement lagging >2cm behind gestational age.
- Ultrasound: Biometric parameters (biparietal diameter, head circumference, abdominal circumference, femur length). An abdominal circumference <10th percentile with head circumference >10th percentile suggests asymmetrical IUGR.
- Doppler studies: Umbilical artery (increased resistance or absent/reversed enddiastolic flow) and middle cerebral artery (decreased resistance) are key prognostic tools.
- Maternal serum markers: Low pregnancyassociated plasma proteinA (PAPPA) and abnormal PlGF/soluble fmslike tyrosine kinase1 (sFlt1) ratios may indicate placental dysfunction.
4.2 Postnatal Evaluation
Infants born with birth weight <10th percentile are assessed for:
- Anthropometric measurements (weight, length, head circumference).
- Blood glucose, calcium, and electrolytes.
- Neonatal complications (hypothermia, respiratory distress, polycythemia).
- Neurodevelopmental followup.
Figure: Ultrasound showing small abdominal circumference with normal head size.
5. Management
5.1 Antenatal
- Close surveillance: Serial ultrasounds every 24weeks, Doppler studies twice weekly if severe.
- Maternal optimization: Control hypertension, administer lowdose aspirin (81mg) for highrisk women, encourage smoking cessation, nutritional counseling.
- Corticosteroids: Betamethasone 12mg IM 24h apart for fetal lung maturity when delivery before 34weeks is anticipated.
- Timed delivery: Based on Doppler findings, gestational age, and fetal wellbeing. Early delivery may be indicated for reversed umbilical artery flow or severe growth restriction.
5.2 Postnatal
- Thermoregulation, glucose monitoring, and supportive care in NICU as needed.
- Nutrition: Early enteral feeding with fortified breast milk or specialized formula to promote catchup growth.
- Longterm followup: Growth monitoring, neurodevelopmental assessments, vision and hearing screening.
6. Prognosis
Outcomes depend on the severity and timing of the restriction, as well as the underlying cause.
- Mild IUGR (10th5th percentile): Often normal neurodevelopment with appropriate postnatal catchup.
- Severe IUGR (<3rd percentile) and earlyonset: Increased risk of perinatal mortality, cerebral palsy, cognitive impairment, and cardiovascular disease later in life.
7. Prevention Strategies
- Preconception counseling for women with chronic hypertension, diabetes, or renal disease.
- Optimizing maternal nutrition and weight gain according to BMI.
- Avoidance of tobacco, alcohol, and illicit drugs.
- Early identification of highrisk pregnancies with lowdose aspirin initiated before 16weeks.
- Regular prenatal care with appropriate screening for placental insufficiency.
8. Key Points to Remember
- IUGR is a failure of a fetus to reach its growth potential; <10th percentile is the conventional threshold.
- Distinguish symmetrical from asymmetrical patterns to guide etiologic workup.
- Umbilical artery Doppler is the most reliable predictor of perinatal outcome.
- Management balances fetal benefits of prolonged gestation against risks of a hostile intrauterine environment.
- Longterm followup is essential; many affected children develop metabolic and neurocognitive sequelae.
9. References
- American College of Obstetricians and Gynecologists. Management of Intrauterine Growth Restriction. ACOG Practice Bulletin No. 222, 2022.
- Lee, A.C. et al. Doppler Ultrasound in the Management of IUGR. *Prenatal Diagnosis*, vol. 41, no. 5, 2021, pp. 663674.
- Royal College of Obstetricians & Gynaecologists. Fetal Growth Restriction. Greentop Guideline No. 31, 2020.
- Halfon, P. et al. Longterm Outcomes of Children with IUGR. *Pediatrics*, 2023; 151(4): e20220285.
- World Health Organization. Maternal and Child Nutrition: Recommendations for IUGR Prevention. WHO Technical Report Series, 2021.
