Intrauterine Growth Restriction (IUGR)

Definition & Classification

• Symmetric IUGR (~20–30%): All parameters reduced proportionally; onset early (< 28 wks); often fetal/chromosomal cause
• Asymmetric IUGR (~70–80%): Head-sparing with reduced abdominal circumference; onset late; typically placental/uteroplacental insufficiency

Etiology

Maternal (~25–30%)

• Hypertensive disorders (preeclampsia, chronic hypertension)
• Diabetes with vascular disease
• Autoimmune conditions (antiphospholipid syndrome, SLE)
• Chronic renal disease
• Severe anemia, malnutrition, underweight
• Smoking, alcohol, cocaine use
• PCOS (OR ~1.77 vs. non-PCOS pregnancies; Assessment and Management of PCOS, p. 136)
• Thrombophilias

Placental (~40%)

• Placental insufficiency / uteroplacental insufficiency (most common)
• Placenta previa, abruption
• Velamentous cord insertion
• Circumvallate placenta

Fetal (~15%)

• Chromosomal anomalies (trisomy 13, 18, 21; Turner syndrome)
• Structural congenital anomalies
• Inborn errors of metabolism
• Multiple gestation (twin-twin transfusion)

Infectious (~5–10%)

• TORCH infections: Toxoplasma, Other (syphilis, VZV, parvovirus B19), Rubella, CMV, Herpes

Pathophysiology

1. Defective trophoblast invasion → inadequate spiral artery remodeling
2. Increased placental vascular resistance → ↑ umbilical artery pulsatility
3. Fetal redistribution response: vasodilation of cerebral/coronary/adrenal circulation ("brain-sparing" = ↓ MCA resistance)
4. Progressive decompensation: absent/reversed end-diastolic flow (AEDF/REDF) in umbilical artery → venous pulsations in ductus venosus → fetal death

Diagnosis

Screening

• Uterine artery Doppler at 20–24 weeks (↑ PI / notching predicts placental insufficiency)
• Serial symphysis-fundal height (SFH) measurements — flattening or lag triggers ultrasound

Ultrasound Biometry

• Abdominal circumference (AC) — most sensitive single parameter
• EFW < 10th percentile (severe < 3rd percentile)
• Serial measurements every 2–4 weeks to assess growth velocity (crossing centiles is as important as absolute value)

Doppler Studies (key for surveillance & timing)

Biophysical Profile (BPP)

• Scores fetal tone, movement, breathing, amniotic fluid, and NST (0–10)
• Score ≤ 4: high risk of acidosis, consider delivery
• Score 6: repeat in 4–6 hours

Management

Antepartum

• Identify and treat underlying cause (e.g., optimize BP in hypertension, treat infection)
• Aspirin (low-dose, 100–150 mg/day from 11–14 weeks): reduces risk of placental IUGR in high-risk women
• No proven intervention improves growth directly once IUGR is established
• Optimize maternal nutrition, stop smoking/drugs
• Corticosteroids if preterm delivery anticipated (< 34 weeks)
• Magnesium sulfate for neuroprotection if < 32 weeks

Surveillance Frequency

Timing of Delivery

Mode of Delivery

• Vaginal delivery is acceptable if no acute compromise
• Continuous electronic fetal monitoring in labor is mandatory
• Low threshold for cesarean section with abnormal Dopplers (AEDF/REDF) or non-reassuring CTG

Complications

Perinatal

• Stillbirth / intrauterine fetal demise (IUFD)
• Birth asphyxia, meconium aspiration
• Hypoglycemia, hypothermia, polycythemia
• Necrotizing enterocolitis (NEC)
• Respiratory distress syndrome (prematurity)
• Neurodevelopmental impairment

Long-term (Barker Hypothesis / Fetal Origins of Adult Disease)

• Hypertension, coronary artery disease
• Type 2 diabetes / insulin resistance
• Obesity
• SGA is associated with ↑ risk of hypertension and diabetes in the offspring (Management of CVD and Pregnancy, p. 78)

Key Points Summary

• IUGR ≠ SGA — IUGR implies pathological growth failure confirmed by Doppler/functional compromise
• Placental insufficiency is the most common cause in developed countries
• Umbilical artery Doppler is the cornerstone of surveillance — AEDF/REDF are delivery triggers
• No treatment restores normal fetal growth; management is surveillance + timely delivery
• Long-term cardiovascular and metabolic risks are significant for both mother and offspring