Fetal Growth Restriction (FGR), previously known as Intrauterine Growth Restriction (IUGR), is a condition in which the fetus fails to achieve its genetically determined growth potential, resulting in an estimated fetal weight (EFW) below the 10th percentile for gestational age.
Classification of FGR
1. Symmetrical FGR (20%)
- Definition: Proportional restriction of growth in both head and body.
- Etiology:
- Early pregnancy insults (First trimester).
- Chromosomal abnormalities (Trisomy 13, 18, 21).
- Congenital infections (TORCH: Toxoplasmosis, Rubella, CMV, Herpes).
- Maternal malnutrition.
- Ultrasound Findings:
- Head circumference (HC) & Abdominal circumference (AC) both reduced.
- Brain growth is also affected.
- Prognosis: Poor, due to permanent fetal cell damage.
2. Asymmetrical FGR (80%)
- Definition: Head growth is preserved, but body growth is restricted.
- Etiology:
- Placental insufficiency (Late pregnancy insult).
- Maternal conditions (Preeclampsia, Chronic hypertension, Diabetes).
- Smoking, Alcohol, Drug use.
- Ultrasound Findings:
- Normal head circumference (HC), but decreased abdominal circumference (AC).
- Brain sparing effect: Blood is shunted to vital organs (Brain, Heart).
- Prognosis: Better than symmetrical FGR if timely intervention is done.
Causes of FGR
1. Maternal Causes:
- Preeclampsia & Hypertension.
- Diabetes Mellitus with vascular complications.
- Anemia & Malnutrition.
- Smoking, Alcohol, Drug use (Cocaine).
2. Fetal Causes:
- Chromosomal abnormalities (Trisomy 13, 18, 21).
- Congenital infections (TORCH group).
- Multiple pregnancy (Twin-to-Twin Transfusion Syndrome).
3. Placental Causes:
- Placental insufficiency (Most common).
- Placental infarction & Abruption.
- Placenta previa.
Diagnosis of FGR
1. Clinical Diagnosis:
- Fundal Height Measurement:
- Discrepancy of >3 cm between fundal height and gestational age suggests FGR.
2. Ultrasound (Gold Standard):
- Estimated Fetal Weight (EFW) <10th percentile for gestational age.
- Amniotic Fluid Index (AFI):
- Oligohydramnios (AFI <5 cm) is common in FGR.
- Doppler Studies:
- Umbilical Artery Doppler (UAD):
- Increased resistance → Early FGR.
- Absent or reversed end-diastolic flow → Severe FGR.
- Middle Cerebral Artery (MCA):
- Low resistance → Brain sparing effect.
- Cerebroplacental Ratio (CPR) <1: Predicts fetal compromise.
Management of FGR
1. Mild FGR (EFW 5th–10th Percentile, Normal Doppler)
- Regular fetal monitoring every 2 weeks.
- Fetal kick count assessment.
- Nutritional supplementation (Protein, Iron, Folic Acid).
2. Moderate to Severe FGR (EFW <5th Percentile, Abnormal Doppler)
- Admit for close monitoring.
- Biweekly Doppler studies & NST.
- Steroids (Betamethasone) for lung maturity if <34 weeks.
3. Indications for Delivery in FGR:
- Absent or reversed umbilical artery Doppler flow.
- Persistent non-reassuring NST.
- Severe oligohydramnios (AFI <2 cm).
- Gestational Age >37 weeks (Planned induction of labor).
- Cesarean section for severe fetal distress.
Complications of FGR
Perinatal Complications:
- Stillbirth & Neonatal Death.
- Meconium Aspiration Syndrome.
- Hypoglycemia & Hypothermia.
- Neonatal Sepsis & Respiratory Distress Syndrome (RDS).
Long-Term Complications:
- Neurodevelopmental Delay.
- Cerebral Palsy.
- Metabolic Syndrome & Cardiovascular Disease in adulthood.
Summary Table: Symmetrical vs. Asymmetrical FGR
|
Feature |
Symmetrical FGR |
Asymmetrical FGR |
|
Timing of Onset |
Early pregnancy |
Late pregnancy |
|
Cause |
Chromosomal, Infections |
Placental Insufficiency, Preeclampsia |
|
Head Circumference (HC) |
↓ Decreased |
Normal (Brain Sparing) |
|
Abdominal Circumference
(AC) |
↓ Decreased |
↓ Decreased |
|
Doppler Findings |
Variable |
Increased Umbilical Artery Resistance |
|
Prognosis |
Poor |
Better with intervention |
Key Takeaways
- FGR = EFW <10th percentile for gestational age.
- Symmetrical FGR is due to genetic or infection causes.
- Asymmetrical FGR is due to placental insufficiency (More common).
- Umbilical artery Doppler is the most important tool for monitoring.
- Delivery is needed if Doppler flow is absent or reversed.
