Doppler interrogation of the uterine arteries at 23 weeks shows persistent bilateral early diastolic notches with elevated resistance indices. The underlying mechanism responsible for this waveform is:
- A Excessive trophoblastic invasion causing arteriovenous shunting
- B Compression of the iliac arteries by the gravid uterus
- C Failure of trophoblastic invasion and conversion of the spiral arteries into low-resistance vessels ✓
- D Maternal vasodilatation from physiological adaptation to pregnancy
Correct answer: C. Failure of trophoblastic invasion and conversion of the spiral arteries into low-resistance vessels
Explanation
In normal pregnancy, extravillous trophoblast invades the spiral arteries, replacing the muscular wall and converting them into flaccid low-resistance vessels. When this fails, the vessels retain their high-resistance character, producing raised pulsatility indices and a protodiastolic notch on uterine artery Doppler. Persistent notching beyond 22 to 24 weeks identifies a population at increased risk of pre-eclampsia and fetal growth restriction, which is why the test is used as a screening tool in high-risk pregnancies.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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