## Routine Second Trimester Antenatal Investigations ### Standard Investigations (All Recommended) | Investigation | Timing | Purpose | Evidence | |---|---|---|---| | OGTT | 24–28 weeks | Screen for gestational diabetes mellitus | Routine in all pregnancies | | Level II ultrasound | 18–22 weeks | Fetal anatomy, anomaly detection, dating | Standard of care | | Indirect Coombs test | First visit + repeat at 28 weeks (Rh-negative) | Detect maternal alloimmunization | Prevents hemolytic disease | | Full blood count | Each trimester | Anemia screening, baseline | Routine | | Serology | First visit | Syphilis, HIV, hepatitis B/C | Mandatory in India | ### Why Amniocentesis is NOT Routine **Key Point:** Amniocentesis is an **invasive procedure** with a small but real risk of miscarriage (~0.1–0.3%). It is **NOT offered to all pregnant women** as a routine screening test. **Indications for Amniocentesis:** - Advanced maternal age (≥35 years) — though now less common with NIPT - Abnormal triple/quadruple screen results - Abnormal aneuploidy risk on NIPT (cell-free fetal DNA testing) - Fetal anomalies on ultrasound suggestive of aneuploidy - Previous child with chromosomal abnormality - Maternal balanced translocation carrier **Clinical Pearl:** First-line screening for chromosomal abnormalities is now **non-invasive prenatal testing (NIPT)** or **combined first-trimester screening** (nuchal translucency + biochemistry at 11–14 weeks), not amniocentesis. Amniocentesis is reserved for **diagnostic confirmation** when screening is abnormal. **High-Yield:** The shift in practice is from invasive (amniocentesis) to non-invasive (NIPT) screening. Routine amniocentesis in all pregnancies is **outdated and not recommended** by any major guideline (ACOG, RCOG, FOGSI). ### Summary Table: What IS vs IS NOT Routine | What IS Routine | What is NOT Routine | |---|---| | OGTT at 24–28 weeks | Amniocentesis in all women | | Level II ultrasound at 18–22 weeks | Routine invasive testing | | Indirect Coombs (Rh-negative) | CVS without indication | | Serology (syphilis, HIV, HBsAg) | Cordocentesis | | NIPT or combined screening (if offered) | — |
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