prenatal test 部分知识点

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Anti-D antibody screening (for Rh-negative women): 28 weeks (instead of Rh D immuneglobulin; Rh D immune globulin is given if no sensitization is detected).

GBS swab screening: 36-37 weeks

Gestational diabetes screening (1-hourGTT, confirmatory 3-hour GTT): 24-28 weeks

• Treatment: Diet, exercise; insulin is first-line therapy (ACOG     is becoming more accepting of metformin and glyburide, but insulin remains     the preferred choice).
  

Cell-free fetal DNA (cffDNA) testing is the most sensitive (>99%) and specific (>99%) screening method for fetal aneuploidies and can be performed from 9–10 weeks onward.

• If immediate screening is desired, cffDNA testing is the best option.
  

• If cffDNA testing indicates increased risk, chorionic villus sampling (CVS) is required for a definitive diagnosis between 10–13 weeks.
  

Chorionic villus sampling (CVS): 10-13 weeks (for early chromosomal screening, not mandatory).

Ultrasound for neural tube defects: 18-22 weeks (optimal at 20 weeks; detectsanencephaly, spina bifida, etc.).

Amniocentesis: ≥15 weeks (optimal at 14-20 weeks).(karyotopicdiagnosis)

Quad screen:15-20 weeks (optimal at 16-18 weeks).

• Note: First-trimester screening for Down syndrome: 9-13 weeks (includes PAPP-A, β-hCG, and nuchal     translucency measurement).
  

Cervical insufficiency management: Cerclage placement at 12-14 weeks (high-risk patients mayrequire placement ≤12 weeks).

1. L/S Ratio (Lecithin/Sphingomyelinratio)

• Testing method: Measured through amniocentesis     to collect amniotic fluid.
• Invasiveness: Yes, amniocentesis is     an invasive procedure.
• Use: Used to assess fetal lung     maturity.
• Applicable gestational weeks:     Typically performed after 32 weeks, especially when early delivery     is considered.
• Maturity standard:
  
  
  
  
  • L/S ratio ≥ 2.0 indicates lung      maturity.
  • ≥32 weeks: L/S ratio begins to      increase.
  • ≥34-35 weeks: L/S ratio ≥ 2      indicates lung maturity.
    

2. Phosphatidylglycerol (PG) Presence

• Testing method: Measured through amniocentesis     to collect amniotic fluid.
• Invasiveness: Yes, amniocentesis is     an invasive procedure.
• Use: Detects the presence of phosphatidylglycerol     (PG), a marker of lung maturity.
• Applicable gestational weeks:     Typically performed after 32 weeks, especially when early delivery     is considered.
• Maturity standard: PG present     indicates lung maturity.
  

3. Lamellar Body Count (LBC)

• Testing method: Measured through amniocentesis     to collect amniotic fluid.
• Invasiveness: Yes, amniocentesis is     an invasive procedure.
• Use: Assesses lung maturity by     counting lamellar bodies in the amniotic fluid.
• Applicable gestational weeks:     Typically performed after 32 weeks, especially in cases of preterm     labor.
• Maturity standard: Higher     lamellar body count indicates lung maturity.
  

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