## Routine First Antenatal Visit Investigations **Key Point:** Amniocentesis is **NOT** a routine first-visit investigation. It is an **invasive diagnostic procedure** reserved for specific indications (advanced maternal age, abnormal screening, fetal anomaly, etc.) and is performed only after informed consent and risk counseling, typically in the second or third trimester. ### Investigations at First Antenatal Visit (8–12 weeks) | Investigation | Purpose | Timing | | --- | --- | --- | | Blood group & Rh typing + IAT | Identify Rh-negative mothers; detect alloimmunization | First visit | | Hemoglobin & PBF | Screen for anemia; assess RBC morphology | First visit | | Urine routine & culture | Detect bacteriuria, proteinuria, glycosuria | First visit | | Blood glucose (fasting/random) | Baseline glucose; screen for overt diabetes | First visit | | VDRL/RPR | Syphilis screening | First visit | | HIV, HBsAg, HCV serology | Infectious disease screening | First visit | | Pap smear (if due) | Cervical cancer screening | First visit | | Transvaginal ultrasound | Confirm viability, dating, rule out ectopic | First visit | **High-Yield:** Amniocentesis is a **second/third-trimester invasive test** with a small risk of miscarriage (~0.1–0.3%); it is never routine and requires specific indication and counseling. ### When Amniocentesis IS Indicated - Advanced maternal age (≥35 years) - Abnormal first-trimester combined screening (high risk) - Abnormal quad screen or integrated screen - Fetal anomaly on ultrasound - Previous child with chromosomal disorder - Carrier status for single-gene disorder **Clinical Pearl:** Non-invasive prenatal testing (NIPT) and sequential/integrated screening have reduced the need for invasive testing in many centers, but when indicated, amniocentesis is performed at 15–18 weeks gestation.
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