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Small for gestational age/large for gestational age

Specialties > Obstetrics

Differential Diagnosis Schema 🧠

Small for Gestational Age (SGA)

  • Constitutional smallness: Small parents, no pathological cause, normal growth velocity.
  • Placental insufficiency: Pre-eclampsia, maternal hypertension, placental abruption leading to restricted blood supply and nutrients.
  • Intrauterine infections: TORCH infections (Toxoplasmosis, Rubella, Cytomegalovirus, Herpes Simplex) leading to fetal growth restriction.
  • Chromosomal abnormalities: Trisomies (e.g., Down syndrome), Turner syndrome causing restricted growth.
  • Maternal factors: Malnutrition, smoking, alcohol, drug use, chronic diseases such as diabetes or renal disease.

Large for Gestational Age (LGA)

  • Maternal diabetes: Pre-existing diabetes or gestational diabetes causing fetal macrosomia due to increased glucose transfer.
  • Genetic factors: Large parents often have large babies, no pathological cause.
  • Excessive maternal weight gain: Leads to increased fetal growth.
  • Post-term pregnancy: Prolonged gestation allows for continued fetal growth beyond the normal term.
  • Fetal overgrowth syndromes: Beckwith-Wiedemann syndrome, associated with macrosomia and other features.

Key Points in History 🥼

Maternal Health and Pregnancy History

  • Pre-existing conditions: Diabetes (risk for LGA), hypertension (risk for SGA).
  • Previous pregnancies: History of SGA or LGA babies, recurrent miscarriages.
  • Gestational age: Accurate dating is crucial for assessing growth.
  • Infections during pregnancy: History of TORCH infections or other significant infections.
  • Maternal lifestyle: Smoking, alcohol, substance use, and nutrition can significantly impact fetal growth.

Fetal Movements and Growth Patterns

  • Reduced fetal movements: May indicate placental insufficiency or fetal compromise.
  • Accelerated growth: Rapid increases in symphysis-fundal height could suggest LGA or polyhydramnios.
  • Serial measurements: Consistent small measurements may indicate SGA; larger measurements suggest LGA.

Background

  • Past Medical History: Hypertension, renal disease, diabetes, or other chronic conditions.
  • Drug History: Medications taken during pregnancy that may impact fetal growth, such as anticonvulsants.
  • Family History: Genetic conditions or history of SGA/LGA in siblings or parents.
  • Social History: Socioeconomic status, access to antenatal care, maternal stress levels.

Possible Investigations 🌡️

Ultrasound Assessment

  • Biometry: Measuring fetal head circumference, abdominal circumference, and femur length to assess growth.
  • Amniotic fluid index: Abnormal levels may indicate SGA (oligohydramnios) or LGA (polyhydramnios).
  • Doppler studies: Assessing placental blood flow, particularly in SGA fetuses where placental insufficiency is suspected.
  • Serial ultrasounds: Monitoring growth over time to differentiate between small but healthy and pathologically small fetuses.

Maternal Blood Tests

  • Glucose tolerance test: To diagnose or rule out gestational diabetes, a key factor in LGA.
  • Infection screening: TORCH screen if intrauterine infection is suspected as a cause of SGA.
  • Thyroid function tests: To assess maternal thyroid status, as abnormalities can affect fetal growth.
  • Full blood count and urea & electrolytes: To check for underlying maternal conditions affecting pregnancy.

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Obstetrics