A 24-year-old primigravida from rural Maharashtra presents for her first antenatal ultrasound at 18 weeks of gestation (by last menstrual period). On transabdominal scanning, the fetus shows bilateral ventriculomegaly (ventricular atrium diameter 12 mm on each side), normal amniotic fluid volume, and a single umbilical artery. The cerebellum appears normal. What is the most appropriate next step in management?

Explanation

## Clinical Significance of Ventriculomegaly at 18 Weeks **Key Point:** Bilateral ventriculomegaly (ventricular atrium diameter ≥10 mm) in the second trimester is an important soft marker for chromosomal abnormalities (trisomy 21, 18, 13) and structural anomalies, particularly when combined with other findings. **High-Yield:** The presence of a single umbilical artery (SUA) is itself a marker for aneuploidy and congenital anomalies; when combined with ventriculomegaly, the risk is significantly elevated. ### Diagnostic Approach | Finding | Significance | |---------|---------------| | Bilateral ventriculomegaly (≥10 mm) | Soft marker for aneuploidy; requires detailed survey | | Single umbilical artery | Associated with trisomy 18, 13; cardiac and renal anomalies | | Normal cerebellum | Does not exclude aneuploidy; ventriculomegaly may be isolated or syndromic | | Normal amniotic fluid | Does not reduce risk; soft markers remain concerning | ### Recommended Management 1. **Detailed anatomical survey** — assess for other structural anomalies (cardiac, renal, skeletal) 2. **Fetal echocardiography** — single umbilical artery is associated with congenital heart disease (VSD, ASD, tetralogy of Fallot) 3. **Counseling on aneuploidy risk** — offer cell-free fetal DNA testing (NIPT) or invasive testing (amniocentesis) if not already done 4. **Serial ultrasound** — monitor progression of ventriculomegaly; mild ventriculomegaly may resolve or remain stable **Clinical Pearl:** Ventriculomegaly detected in the second trimester with concurrent soft markers (SUA, echogenic bowel, renal pyelectasis) warrants aggressive investigation; isolated mild ventriculomegaly may have better prognosis but still requires detailed anatomy and aneuploidy assessment. **Warning:** Do NOT reassure based on normal cerebellum alone — cerebellar size does not exclude aneuploidy-related ventriculomegaly. Do NOT recommend termination without comprehensive evaluation and parental counseling.