What is the management approach for a fetus diagnosed with Intrauterine Growth Restriction (IUGR)?

Management of Intrauterine Growth Restriction (IUGR)

The management of IUGR centers on serial umbilical artery Doppler surveillance to guide timing of delivery, with delivery timing determined by Doppler findings and gestational age: 38-39 weeks for mild IUGR with normal Doppler, 37 weeks for decreased diastolic flow, 33-34 weeks for absent end-diastolic flow, and 30-32 weeks for reversed end-diastolic flow. 1

Initial Diagnosis and Workup

Define IUGR as estimated fetal weight or abdominal circumference below the 10th percentile using population-based references like Hadlock. 1 Once diagnosed, the workup differs based on timing:

Early-Onset IUGR (<32 weeks)

• Perform a detailed anatomic ultrasound examination, as chromosomal abnormalities or malformations account for approximately 20% of cases 1
• Offer chromosomal microarray analysis for all unexplained isolated IUGR diagnosed before 32 weeks 1
• If fetal malformation or polyhydramnios is present, offer diagnostic testing regardless of gestational age 1
• Test for cytomegalovirus via PCR if amniocentesis is performed for unexplained IUGR 1
• Do not routinely screen for toxoplasmosis, rubella, or herpes unless other risk factors exist 1

Late-Onset IUGR (≥32 weeks)

• Chromosomal microarray is not routinely indicated unless malformations are present 1
• Focus on placental insufficiency as the primary etiology 2

Surveillance Strategy

Umbilical artery Doppler is the cornerstone of surveillance and significantly reduces perinatal mortality. 1, 3

Doppler Assessment Frequency

• Normal umbilical artery Doppler or mild IUGR (EFW 3rd-10th percentile): Weekly Doppler evaluation 1, 3
• Decreased end-diastolic velocity (flow ratios >95th percentile) or severe IUGR (EFW <3rd percentile): Weekly Doppler 1
• Absent end-diastolic velocity: Doppler 2-3 times per week 1
• Reversed end-diastolic velocity: Daily to twice-daily monitoring with hospitalization 1

Cardiotocography (NST/BPP)

• Weekly cardiotocography after viability for IUGR without absent/reversed flow 1, 3
• Increase frequency to at least 1-2 times daily when absent or reversed end-diastolic velocity is present 1

Other Doppler Parameters

Do not use ductus venosus, middle cerebral artery, or uterine artery Doppler for routine clinical management decisions, though these may provide additional information in research settings 1. Note that in early-onset IUGR, venous Doppler abnormalities reflect progressive deterioration, while in late-onset IUGR, cerebral Doppler changes become more prominent 2.

Timing of Delivery

Delivery timing is dictated by umbilical artery Doppler findings and gestational age, balancing prematurity risks against in utero deterioration:

Normal Umbilical Artery Doppler

• EFW 3rd-10th percentile with normal Doppler: Deliver at 38-39 weeks 1, 3

Abnormal Umbilical Artery Doppler

• Decreased diastolic flow (elevated resistance but forward flow throughout): Deliver at 37 weeks 1, 3
• Severe IUGR (EFW <3rd percentile) even with normal Doppler: Deliver at 37 weeks 1, 3
• Absent end-diastolic velocity: Deliver at 33-34 weeks 1, 3
• Reversed end-diastolic velocity: Deliver at 30-32 weeks 1, 3

Each additional day in utero before 32 weeks increases intact survival by 1-2%, making expectant management valuable when surveillance remains reassuring. 3

Antenatal Interventions

Corticosteroids

Administer antenatal corticosteroids if delivery is anticipated before 34 weeks or if absent/reversed end-diastolic flow is detected at <34 weeks. 1, 3 Also give corticosteroids between 34-36 6/7 weeks if at risk of delivery within 7 days without prior course 1.

Monitor closely for 48-72 hours after steroid administration, as approximately two-thirds of cases with absent flow may show transient return of end-diastolic flow due to altered placental vascular tone. 1, 3

Magnesium Sulfate

Administer intrapartum magnesium sulfate for neuroprotection when delivery occurs before 32 weeks. 1, 3

Ineffective Interventions

Do not use low-molecular-weight heparin, sildenafil, or activity restriction for treatment or prevention of IUGR, as evidence does not support benefit. 1

Mode of Delivery

For IUGR with absent or reversed end-diastolic velocity, strongly consider cesarean delivery based on the clinical scenario, as these fetuses tolerate labor poorly and have high risk for acidosis and low Apgar scores 1, 3, 4.

Continuous intrapartum fetal heart rate monitoring is mandatory regardless of delivery mode due to limited fetal reserve and high risk of hypoxia 5, 4.

Special Considerations

Reversed End-Diastolic Velocity Management

When reversed flow is detected:

• Hospitalize immediately 1
• Administer corticosteroids 1
• Perform cardiotocography at least 1-2 times daily 1
• Consider delivery based on complete clinical picture and gestational age 1

Maternal Comorbidities

Monitor closely for development of hypertensive disorders, as up to 70% of early-onset IUGR cases have maternal hypertension at delivery. 3 Treat underlying maternal conditions and ensure adequate nutrition 5.

Neonatal Preparation

Ensure pediatric team attendance at delivery due to high risk of meconium aspiration, low Apgar scores, and metabolic disorders. 4

Common Pitfalls

• Do not rely on fundal height alone—a lag of 4 cm or more suggests IUGR but ultrasound biometry is the gold standard 5
• Do not confuse IUGR with constitutionally small (SGA) fetuses—Doppler assessment helps distinguish pathologic growth restriction from normal small size 6, 7
• Do not delay delivery in the setting of reversed flow beyond 32 weeks unless there are compelling reasons, as risk of stillbirth increases substantially 1
• Do not use ductus venosus or middle cerebral artery Doppler to make delivery decisions in routine practice, despite their research interest 1