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

Management of Fetal Growth Restriction (IUGR)

The management of Intrauterine Growth Restriction (IUGR) requires a structured approach based on gestational age, severity of growth restriction, and umbilical artery Doppler findings to optimize fetal outcomes and reduce morbidity and mortality. 1

Definition and Diagnosis

• IUGR should be defined as an ultrasonographic estimated fetal weight (EFW) or abdominal circumference (AC) below the 10th percentile for gestational age 2
• Population-based fetal growth references (such as Hadlock) should be used in determining fetal weight percentiles 2
• A detailed obstetrical ultrasound examination should be performed with early-onset IUGR (<32 weeks of gestation) to identify possible fetal or chromosomal abnormalities, which account for approximately 20% of IUGR cases 2, 1

Diagnostic Testing

• Fetal diagnostic testing, including chromosomal microarray analysis (CMA), should be offered when IUGR is detected with fetal malformation, polyhydramnios, or both, regardless of gestational age 2
• Prenatal diagnostic testing with CMA should be offered when unexplained isolated IUGR is diagnosed at <32 weeks of gestation 2
• PCR for cytomegalovirus is recommended in women with unexplained IUGR who elect diagnostic testing with amniocentesis 2
• Screening for toxoplasmosis, rubella, or herpes is not recommended in pregnancies with IUGR in the absence of other risk factors 2

Surveillance Protocol

• Once IUGR is diagnosed, serial umbilical artery Doppler assessment should be performed to assess for deterioration 2
• For IUGR with decreased end-diastolic velocity or severe IUGR (EFW <3rd percentile): weekly umbilical artery Doppler evaluation 2
• For IUGR with absent end-diastolic velocity (AEDV): Doppler assessment 2-3 times per week 2
• For IUGR with reversed end-diastolic velocity (REDV): hospitalization, administration of antenatal corticosteroids, heightened surveillance with cardiotocography at least 1-2 times per day 2
• Weekly cardiotocography testing after viability for IUGR without AEDV/REDV, with increased frequency when IUGR is complicated by AEDV/REDV or other comorbidities 2
• Doppler assessment of the ductus venosus, middle cerebral artery, or uterine artery is not recommended for routine clinical management of early- or late-onset IUGR 2

Timing of Delivery

• For IUGR with EFW between the 3rd and 10th percentile and normal umbilical artery Doppler: delivery at 38-39 weeks of gestation 2
• For IUGR with decreased diastolic flow but without AEDV/REDV or with severe IUGR (EFW <3rd percentile): delivery at 37 weeks of gestation 2
• For IUGR with absent end-diastolic velocity: delivery at 33-34 weeks of gestation 2
• For IUGR with reversed end-diastolic velocity: delivery at 30-32 weeks of gestation 2

Mode of Delivery and Intrapartum Management

• For pregnancies with IUGR complicated by AEDV/REDV, cesarean delivery should be considered based on the entire clinical scenario 2
• Continuous fetal monitoring during labor is essential as IUGR fetuses can quickly decompensate once uterine contractions have started 3

Antenatal Interventions

• Antenatal corticosteroids are recommended if delivery is anticipated before 33 6/7 weeks of gestation or for pregnancies between 34 0/7 and 36 6/7 weeks of gestation in women at risk of preterm delivery within 7 days 2
• Intrapartum magnesium sulfate for fetal and neonatal neuroprotection is recommended for women with pregnancies that are <32 weeks of gestation 2

Prevention and Treatment

• Low-dose aspirin is recommended for women at increased risk of preeclampsia, which may also reduce the risk of IUGR 1
• Low-molecular-weight heparin is not recommended for the sole indication of prevention of recurrent IUGR 2
• Sildenafil or activity restriction is not recommended for in utero treatment of IUGR 2

Prognostic Factors

• The single most important prognostic factor in preterm fetuses with growth restriction is the gestational age at delivery, with an increase of 1-2% in intact survival for every additional day spent in utero up until 32 weeks of gestation 1
• IUGR is associated with increased risk of perinatal mortality and morbidity, with the stillbirth rate approximately 1.5% in fetuses with weights below the 10th percentile, which is twice the rate in fetuses with normal growth 2
• Maternal hypertensive disease is common in early-onset IUGR (present in 50-70% of cases) and is associated with poorer outcomes 1

Management Algorithm

1. Confirm IUGR diagnosis (EFW or AC <10th percentile)
2. Perform detailed ultrasound to rule out anomalies
3. Offer appropriate genetic testing based on gestational age and findings
4. Initiate surveillance with umbilical artery Doppler and cardiotocography
5. Adjust surveillance frequency based on Doppler findings
6. Time delivery according to Doppler findings and gestational age
7. Administer antenatal corticosteroids and magnesium sulfate when indicated
8. Choose delivery mode based on fetal status and obstetric factors