What are the management strategies and potential complications of intrauterine growth retardation (IUGR) in a high-risk pregnancy?

Intrauterine Growth Restriction: High-Risk Pregnancy Management

Fetal growth restriction (FGR)—the preferred term over IUGR—represents a high-risk pregnancy because it doubles the stillbirth rate to 1.5% for fetuses below the 10th percentile and increases it to 2.5% for those below the 5th percentile, while also significantly elevating risks of perinatal asphyxia, severe acidosis, low Apgar scores, NICU admissions, and long-term metabolic and neurodevelopmental complications. 1

Why FGR Creates High-Risk Pregnancy

Immediate Perinatal Risks

• Mortality: Fetuses with weights below the 10th percentile face a 2-fold increased stillbirth risk compared to normally growing fetuses 1
• Severe FGR (EFW <3rd percentile) carries stillbirth rates up to 2.5% 1, 2
• Preterm FGR compounds risk with 2- to 5-fold increased perinatal death rates compared to term FGR 1
• Acute neonatal complications include perinatal asphyxia, hypothermia, hypoglycemia, polycythemia, severe acidosis at birth, and low 5-minute Apgar scores 1, 3, 4

Long-Term Health Consequences

• Metabolic programming increases future risk of metabolic syndrome, type 2 diabetes, obesity, hypertension, dyslipidemia, and premature cardiovascular disease 1, 5, 4
• Neurodevelopmental handicaps occur more frequently, particularly with early-onset growth delay and prematurity 3, 4
• Endocrine sequelae include short stature, premature adrenarche, and polycystic ovarian syndrome 4

Underlying Pathophysiology

• Placental insufficiency from suboptimal maternal-placental perfusion accounts for 25-30% of all FGR cases 1, 6
• Chromosomal disorders and congenital malformations are responsible for approximately 20% of FGR cases 1, 6
• Maternal factors including hypertensive disorders, chronic hypertension, diabetes, chronic kidney disease, and autoimmune disorders contribute significantly 1, 6

Evidence-Based Management Algorithm

Diagnostic Approach

Terminology: Use "fetal growth restriction (FGR)" for prenatal diagnosis, not "intrauterine growth restriction (IUGR)"; reserve "small for gestational age (SGA)" for newborns with birthweight <10th percentile 1, 2

Diagnostic criteria:

• FGR diagnosis: EFW or abdominal circumference (AC) <10th percentile for gestational age 1, 7, 2
• Severe FGR: EFW <3rd percentile 1, 7, 2
• Pathological confirmation: Abnormal umbilical artery Doppler (elevated pulsatility index, absent or reversed end-diastolic velocity) confirms placental insufficiency 7, 2
• Growth velocity: AC change <5mm over 14 days or >30% reduction in growth velocity indicates progressive pathology 7, 2

Surveillance Protocol Based on Severity

For EFW 3rd-10th percentile with normal umbilical artery Doppler:

• Perform umbilical artery Doppler every 1-2 weeks initially 7, 2
• If stable, extend interval to every 2-4 weeks 7, 2
• Weekly cardiotocography (NST) after viability 1
• Delivery timing: 38-39 weeks of gestation 1, 2

For severe FGR (EFW <3rd percentile) with normal Doppler:

• Weekly umbilical artery Doppler evaluation 7, 2
• Weekly cardiotocography 7, 2
• Delivery timing: 37 weeks of gestation 1

For FGR with decreased diastolic flow (but not absent/reversed):

• Weekly cardiotocography, increasing frequency with comorbidities 1
• Serial umbilical artery Doppler monitoring 1
• Delivery timing: 37 weeks of gestation 1

For FGR with absent end-diastolic velocity (AEDV):

• Doppler assessment 2-3 times per week 7, 2
• Increased frequency of cardiotocography 1
• Consider hospital admission if surveillance >3 times weekly is needed 7
• Delivery timing: 33-34 weeks of gestation 1, 2

For FGR with reversed end-diastolic velocity (REDV):

• Intensive Doppler monitoring 2-3 times per week 7, 2
• Frequent cardiotocography 1
• Delivery timing: 30-32 weeks of gestation 1, 2

Additional Monitoring Components

Biophysical profile (BPP): Provides immediate assessment of fetal well-being; reassuring BPP associated with very low risk of fetal loss over succeeding week 1

Amniotic fluid volume: Chronic marker of fetal well-being; oligohydramnios suggests chronic placental dysfunction and worsening severity 1, 2

Middle cerebral artery Doppler: Decreased impedance suggests "brain-sparing" effect; cerebroplacental ratio helps identify fetuses at increased risk for cesarean delivery due to abnormal fetal heart rate patterns and neonatal acidosis 1, 2

Antenatal Interventions

Corticosteroids: Administer if delivery anticipated before 33 6/7 weeks or between 34 0/7 and 36 6/7 weeks in women at risk of preterm delivery within 7 days who haven't received prior course 1

Magnesium sulfate: Give intrapartum for fetal neuroprotection when delivery anticipated <32 weeks of gestation 1

Low-dose aspirin: May prevent FGR in certain high-risk patients when started early in pregnancy 1

Mode of delivery: For FGR with absent/reversed end-diastolic velocity, consider cesarean delivery based on entire clinical scenario including gestational age, fetal status, and maternal factors 1

Genetic Evaluation

Early-onset FGR (<32 weeks): Consider chromosomal microarray analysis (CMA), especially when accompanied by fetal malformations or polyhydramnios 7

Detailed fetal structural survey: Essential as approximately 10-20% of fetuses with FGR have congenital anomalies or chromosomal disorders 1, 6

Common Mistakes to Avoid

Critical Pitfalls

1. Using umbilical artery Doppler for screening in low-risk populations: Doppler screening should NOT be used routinely in low-risk women to predict FGR; it is only beneficial once FGR is suspected in high-risk pregnancies 1

2. Relying solely on middle cerebral artery or ductus venosus Doppler: While these vessels have prognostic value, umbilical artery Doppler is the only vessel proven in randomized trials to reduce perinatal deaths (RR 0.71; 95% CI 0.52-0.98) and should be the primary surveillance tool 1

3. Delaying delivery inappropriately: Specific gestational age cutoffs exist based on Doppler findings—failure to deliver at recommended times increases stillbirth risk 1

• Reversed end-diastolic velocity: deliver 30-32 weeks
• Absent end-diastolic velocity: deliver 33-34 weeks
• Decreased diastolic flow or severe FGR: deliver 37 weeks
• Mild FGR with normal Doppler: deliver 38-39 weeks

4. Confusing FGR with constitutionally small fetuses: Not all SGA fetuses have pathological growth restriction; umbilical artery Doppler helps differentiate hypoxic growth-restricted fetuses from non-hypoxic small fetuses, reducing unnecessary interventions 7, 2

5. Inadequate surveillance intervals: Growth assessment should occur no more frequently than every 2 weeks (preferably every 3-4 weeks) due to inherent measurement error; more frequent measurements lead to false-positive diagnoses of growth deceleration 1

6. Ignoring growth velocity: Fetuses crossing centiles downward or showing inadequate interval growth may have FGR even if EFW remains >10th percentile 7, 2

7. Failing to assess for maternal risk factors: Active and passive tobacco exposure, maternal stress, prolonged standing/working hours, hypertensive disorders, and vascular disease are modifiable or treatable contributors 8

8. Inadequate neonatal preparation: FGR infants require interdisciplinary follow-up for acute complications (hypoglycemia, hypothermia, polycythemia) and long-term risks of neurodevelopmental and metabolic disease 2, 3, 4

9. Using outdated terminology: The term "intrauterine growth restriction (IUGR)" should be abandoned in favor of "fetal growth restriction (FGR)" for prenatal diagnosis 1, 2

10. Neglecting long-term cardiovascular risk counseling: Women with prior FGR pregnancies have increased risk for hyperlipidemia, hypertriglyceridemia, insulin resistance, and future cardiovascular disease; this warrants long-term preventive care 1