A woman with an obstetric score of G2P1 comes to the clinic at 14 weeks of gestation for her antenatal checkup. A uterine artery doppler was suggested by the doctor. What would it detect?

Correct Answer: C. Early onset preeclampsia

Uterine artery Doppler performed in the second trimester (11–14 weeks) is a screening tool for early-onset preeclampsia (EOP), not a diagnostic test. At 14 weeks, the patient is in the optimal window for this assessment. The test measures pulsatility index (PI) and resistance index (RI) of the uterine arteries and identifies the presence of a diastolic notch (abnormal flow pattern). Abnormal Doppler findings (elevated PI/RI or bilateral notches) indicate impaired placentation and trophoblastic invasion, which is the pathophysiological hallmark of preeclampsia. Early-onset preeclampsia (before 34 weeks) is strongly associated with placental insufficiency and abnormal uterine artery Doppler patterns. This screening allows identification of high-risk pregnancies for intensified monitoring and prophylactic interventions (aspirin, calcium supplementation per Indian guidelines). Late-onset preeclampsia, by contrast, is typically associated with normal Doppler findings because it arises from maternal constitutional factors rather than placental pathology. The timing of Doppler assessment (second trimester) and the pathophysiological basis make early-onset preeclampsia the correct answer.

Why the other options are wrong

A. Late – onset preeclampsia — Late-onset preeclampsia (≥34 weeks) is primarily a maternal constitutional disorder, not a placental insufficiency disorder. It shows normal uterine artery Doppler findings because trophoblastic invasion is adequate. Second-trimester Doppler screening has poor predictive value for late-onset disease. This is the NBE trap—confusing the timing and pathophysiology of preeclampsia subtypes. B. Placenta accreta — Placenta accreta is detected by transvaginal ultrasound (loss of retroplacental hypoechoic zone, abnormal placental lacunae, bladder interface disruption), not uterine artery Doppler. While both are second-trimester screening tests, Doppler assesses placental perfusion patterns, not placental invasion depth. This option tests whether students confuse different ultrasound modalities. D. Fetal growth restriction — Fetal growth restriction (FGR) is detected by umbilical artery Doppler and middle cerebral artery Doppler, not uterine artery Doppler. Although abnormal uterine artery Doppler increases FGR risk, the Doppler finding itself predicts preeclampsia and placental insufficiency, not FGR alone. This is a common confusion in Doppler interpretation.

High-Yield Facts

Mnemonics

DOPPLER TIMING & PATHOLOGY Diastolic notch + Old gestation (11–14 weeks) = Preeclampsia Early onset; Late onset has Low risk; Early onset has Risk from placenta. UTERINE ARTERY DOPPLER RULE Uterine artery → Early preeclampsia; Umbilical artery → FGR; Middle cerebral → Cerebral perfusion. Use this to distinguish which Doppler detects what.

NBE Trap

NBE pairs "uterine artery Doppler" with "late-onset preeclampsia" to trap students who know Doppler is used in preeclampsia screening but confuse the pathophysiology: early-onset is placental (abnormal Doppler), late-onset is maternal (normal Doppler). The second-trimester timing is the key discriminator.

Clinical Pearl

In Indian antenatal clinics, abnormal second-trimester uterine artery Doppler in a low-risk primigravida (like this G2P1) should trigger aspirin prophylaxis and intensified monitoring—this simple screening prevents maternal mortality in resource-limited settings where eclampsia remains a leading cause of maternal death.

_Reference: DC Dutta's Textbook of Obstetrics, 8th ed., Ch. 24 (Hypertensive Disorders in Pregnancy); FOGSI Guidelines on Preeclampsia Screening and Management_