What is the management approach for a pregnant woman with intrauterine growth retardation (IUGR)?

Management of Intrauterine Growth Restriction (IUGR)

The management of IUGR centers on serial ultrasound surveillance with umbilical artery Doppler assessment, followed by timely delivery based on Doppler findings and gestational age—this approach significantly reduces perinatal mortality. 1, 2

Diagnostic Confirmation and Initial Workup

Define IUGR as estimated fetal weight (EFW) or abdominal circumference (AC) below the 10th percentile for gestational age, with severe IUGR defined as EFW below the 3rd percentile. 1, 3, 4

Once IUGR is suspected:

• Perform a detailed fetal anatomic survey immediately, as 10-20% of IUGR cases are associated with congenital anomalies or chromosomal disorders. 3, 2
• Offer chromosomal microarray analysis (CMA) for early-onset IUGR diagnosed before 32 weeks, particularly when accompanied by fetal malformations or polyhydramnios. 3, 2
• Evaluate for maternal hypertensive disorders, as up to 70% of early-onset IUGR cases develop maternal hypertension by delivery. 2

Surveillance Protocol

Implement weekly umbilical artery Doppler assessment as the cornerstone of fetal surveillance—this is a Level A recommendation that significantly decreases perinatal mortality. 1, 2

The surveillance intensity depends on severity:

• For EFW between 3rd-10th percentile with normal Doppler: Weekly umbilical artery Doppler initially, then every 2-4 weeks if stable, plus weekly cardiotocography after viability. 3, 4, 2
• For severe IUGR (EFW <3rd percentile) with normal Doppler: Weekly umbilical artery Doppler and weekly cardiotocography. 3, 4
• For absent or reversed end-diastolic velocity (AEDV/REDV): Increase Doppler assessment to 2-3 times per week and consider hospital admission if surveillance more than 3 times weekly is needed. 4, 2

Use biophysical profile (BPP) for immediate assessment of fetal well-being, particularly after viability—a reassuring BPP indicates very low risk of fetal loss over the succeeding week. 1, 3 An abnormal BPP is a strong argument for delivery, though gestational age must be factored into this decision. 1

Monitor for declining growth velocity (AC change <5 mm over 14 days or >30% reduction crossing centiles), as this suggests worsening placental insufficiency requiring more intensive surveillance or delivery. 4

Antenatal Interventions

No preventative treatments or medications effectively treat IUGR itself—management relies entirely on surveillance and timely delivery. 2

However, provide perinatal support medications:

• Administer antenatal corticosteroids if delivery is anticipated before 33 6/7 weeks, or between 34 0/7 and 36 6/7 weeks in women at risk of delivery within 7 days who haven't received a prior course (GRADE 1A recommendation). 3, 2
• Give intrapartum magnesium sulfate for fetal neuroprotection when delivery is anticipated before 32 weeks of gestation (GRADE 1A recommendation). 3, 2
• After corticosteroid administration for AEDV/REDV, observe closely for 48-72 hours, as approximately two-thirds of cases show transient return of end-diastolic flow. 2

Avoid ineffective interventions: Do not use low-molecular-weight heparin for recurrent IUGR prevention, sildenafil for in utero treatment, or bed rest/activity restriction (all GRADE 1B recommendations against use). 2

Delivery Timing Based on Doppler Findings

The timing of delivery is the single most important management decision and should be based on umbilical artery Doppler findings and gestational age:

• Normal Doppler with EFW 3rd-10th percentile: Deliver at 38-39 weeks. 3, 2
• Severe IUGR (EFW <3rd percentile) with normal Doppler: Deliver at 37 weeks. 3, 2
• Absent end-diastolic velocity (AEDV): Deliver at 33-34 weeks if fetal surveillance remains reassuring. 3, 2
• Reversed end-diastolic velocity (REDV): Deliver at 30-32 weeks if fetal surveillance remains reassuring. 3, 2

Each additional day in utero before 32 weeks increases intact survival by 1-2%, making the balance between prematurity risks and ongoing placental insufficiency critical. 2

Mode of Delivery

Consider cesarean delivery for IUGR complicated by AEDV or REDV, based on the entire clinical scenario including gestational age, fetal surveillance results, and maternal factors. 2 These fetuses tolerate labor poorly due to compromised placental reserve.

Critical Pitfalls to Avoid

Do not rely on a single ultrasound measurement—serial evaluations are essential to assess whether the fetus is compensating or deteriorating, as decreasing percentile growth suggests need for more intensive monitoring or delivery. 1

Umbilical artery Doppler is crucial for differentiating the hypoxic growth-restricted fetus from the constitutionally small but healthy fetus, thereby reducing unnecessary interventions. 4 Without Doppler assessment, you risk either premature delivery of a healthy small fetus or delayed delivery of a compromised fetus.

Recognize that middle cerebral artery (MCA) Doppler showing brain-sparing physiology (decreased pulsatility index) may precede stillbirth in late-onset IUGR after 34 weeks, warranting increased surveillance frequency. 1

For early-onset IUGR, retrospective data show that stillbirths typically follow a progression of worsening umbilical artery Doppler, then ductus venosus Doppler abnormalities, then abnormal BPP—but precise management directives for these preterm gestations remain limited by evidence. 1