A 28-year-old multigravida at 34 weeks of gestation is referred from a peripheral clinic with a diagnosis of transverse lie. The patient is asymptomatic, with no vaginal bleeding or leaking of amniotic fluid. Fetal heart rate is 150 bpm. What is the most appropriate investigation to confirm the diagnosis and assess fetal and maternal status?

Explanation

## Investigation of Choice for Suspected Transverse Lie at 34 Weeks ### Clinical Context Transverse lie at 34 weeks is a significant obstetric finding requiring confirmation and comprehensive assessment. The patient is currently asymptomatic, but transverse lie carries risks of cord prolapse, placental abruption, and the need for cesarean delivery. ### Why Transabdominal Ultrasound Is Correct **Key Point:** Transabdominal ultrasound is the gold standard for confirming fetal presentation, measuring amniotic fluid volume, identifying placental location (critical to exclude placenta previa, which is associated with transverse lie), and assessing fetal well-being. **High-Yield:** Ultrasound in transverse lie at 34 weeks provides: - **Definitive confirmation** of transverse orientation (fetal spine perpendicular to maternal spine; head and buttocks in lateral position) - **Fetal biometry** and estimated weight (prognostic for spontaneous version likelihood and delivery planning) - **Amniotic fluid volume** assessment (polyhydramnios increases risk of transverse lie and cord prolapse) - **Placental location** (placenta previa is present in ~5–10% of transverse lie cases and mandates cesarean delivery) - **Fetal anomaly screening** (transverse lie is associated with congenital anomalies in ~10% of cases) - **Umbilical cord position** (assess for cord prolapse risk) **Clinical Pearl:** At 34 weeks, spontaneous version to vertex occurs in ~50% of transverse lie cases if no contraindications exist (e.g., placenta previa, previous cesarean, polyhydramnios). Ultrasound assessment guides counseling on expectant management vs. external cephalic version (ECV) vs. planned cesarean delivery. **Mnemonic: TRANSVERSE LIE ULTRASOUND CHECKLIST — "FETAL MAPS"** - **F**etal position (confirm transverse) - **E**stimated weight and biometry - **T**one and movement (well-being) - **A**mniotic fluid volume - **L**ocation of placenta - **M**aternal uterine anatomy (fibroids, anomalies) - **A**nomalies (fetal) - **P**ath to delivery (cord, presentation) - **S**peed of version (spontaneous vs. assisted) ### Why Other Options Are Suboptimal | Investigation | Limitation | | --- | --- | | Abdominal X-ray | Exposes fetus to ionizing radiation; does not assess soft tissue (placenta, amniotic fluid); poor visualization of fetal skeleton; not indicated for presentation confirmation | | Leopold's maneuvers alone | Clinical examination is operator-dependent and may be inaccurate, especially in obese patients or with polyhydramnios; does not assess placental location, fetal anomalies, or amniotic fluid volume | | Transvaginal ultrasound | Primarily used for cervical length assessment and preterm birth risk; does NOT confirm fetal presentation or assess placental location; transabdominal approach is superior for presentation assessment | **Warning:** Transverse lie is a contraindication to vaginal delivery. Relying on clinical examination alone (Leopold's maneuvers) without imaging confirmation risks misdiagnosis and inappropriate management.