Pregnancy Amniocentesis Ultrasound Scan

• Purpose: Detect chromosomal or genetic conditions early in pregnancy.
• Timing: Performed between weeks 15–20 of gestation.
• Accuracy: Over 99 % accurate for Down syndrome and other major trisomies.
• Guidance: Real-time ultrasound ensures needle placement is precise and fetal safety is maximised.

This dual-procedure combines:

1. Ultrasound Scan – visualises baby, placenta, and amniotic sac.
2. Amniocentesis – withdraws 15–20 ml of amniotic fluid for lab testing.

How Ultrasound Guides the Amniocentesis

• Continuous real-time imaging helps the radiologist avoid the fetus, umbilical cord, and major blood vessels.
• Determines the ideal puncture site on the maternal abdomen.

Difference Between Diagnostic and Screening Tests

• Screening (e.g., NIPT, first-trimester combined test) estimates risk.
• Diagnostic – amniocentesis gives a definitive result for specific chromosomal or genetic disorders.

Role of Genetic Amniotic Fluid Analysis

• Cultured fetal cells undergo karyotyping, microarray, or targeted DNA tests.
• Detects Down syndrome, Edwards syndrome, Patau syndrome, and hundreds of single-gene disorders.

1. Genetic Amniocentesis – chromosomal or micro-array analysis.
2. Lung Maturity Amniocentesis – measures phosphatidylglycerol or L/S ratio after 32 weeks.
3. Fetal Infection Testing – PCR for CMV, toxoplasmosis, parvovirus.

• Fetal position & heart rate
• Placenta localisation
• Amniotic fluid volume (AFI)
• Umbilical cord insertion site
• Maternal vessels to avoid

• Confirm Down syndrome (Trisomy 21)
• Diagnose neural tube defects (spina bifida, anencephaly) via AFP & AChE
• Assess fetal lung maturity before early delivery
• Detect inherited metabolic disorders (Tay-Sachs, Gaucher)

• 99 %+ accuracy for major chromosomal anomalies.
• Enables early intervention planning (prenatal surgery, delivery at tertiary centre).
• Supports informed decision-making (continue pregnancy, prepare for special care, or consider options).

• Drink 2 glasses of water 1 hour before scan (full bladder improves visualisation).
• Bring previous ultrasound & blood test reports.
• No fasting required.
• Wear loose, two-piece clothing for easy abdomen access.

• Valid obstetrician referral.
• Signed informed consent form.
• Rh-negative mothers: inform team to arrange Anti-D immunoglobulin within 72 hours post-procedure.

You are eligible if you meet any of the following:

• Maternal age ≥35 years at delivery.
• Positive NIPT or first-trimester screening.
• Previous child with chromosomal anomaly.
• Parental balanced chromosomal rearrangement.
• Abnormal ultrasound finding (e.g., cystic hygroma, absent nasal bone).

• Avoid procedure if active vaginal infection or chorioamnionitis.
• Disclose bleeding disorders or anticoagulant use.
• Inform team early about twin or higher-order pregnancy for special technique.

• Miscarriage risk: <0.5 % when performed by experienced hands.
• Minor side effects: Cramping, spotting, or leakage of amniotic fluid (usually self-limiting).
• Infection: Rare (<1 in 1,000).
• Limitations: Cannot detect all genetic disorders or structural anomalies.