First Trimester Uterine Artery Doppler PI 2.235: Interpretation and Management

Understanding the Clinical Significance

A uterine artery pulsatility index of 2.235 in the first trimester indicates elevated placental vascular resistance, identifying this pregnancy as high-risk for developing fetal growth restriction (FGR) and early-onset preeclampsia, according to the American College of Obstetricians and Gynecologists, warranting initiation of low-dose aspirin prophylaxis before 16 weeks and enhanced surveillance throughout pregnancy 1.
Elevated placental impedance, as reflected by a PI of 2.235, is associated with abnormal trophoblastic invasion of maternal spiral arterioles, which normally should decrease impedance progressively with advancing gestational age 1.

The American College of Obstetricians and Gynecologists recommends starting low-dose aspirin immediately, with five of six international guidelines (83%) recommending low-dose aspirin for prevention of small-for-gestational-age (SGA) infants, with three specifying initiation by 16 weeks 3.
Administer 75-160 mg of aspirin daily, taken in the evening to maximize efficacy based on randomized controlled trial evidence, as recommended by the American College of Obstetricians and Gynecologists 3, 4.
Aspirin must be started before 16 weeks (ideally) or no later than 20 weeks to provide benefit, according to the American College of Obstetricians and Gynecologists 3, 4.

Implement serial fundal height measurements on a customized chart starting at 22-26 weeks, with ultrasound if measurements fall below the 10th centile or show static/slow growth, as recommended by the American College of Obstetricians and Gynecologists 3, 4.
Schedule growth ultrasounds every 3-4 weeks starting in the second trimester to detect FGR early, according to the American College of Obstetricians and Gynecologists 3, 4.

If FGR is suspected, immediately initiate umbilical artery Doppler surveillance, as this is the primary vessel with Level I evidence for reducing perinatal mortality, as recommended by the American College of Obstetricians and Gynecologists 5.
The American College of Obstetricians and Gynecologists recommends umbilical artery Doppler as the primary vessel to observe in FGR, not continued uterine artery assessment 5.

If preeclampsia develops, perform fetal biometry, amniotic fluid volume, and both uterine and umbilical artery Doppler as a one-time comprehensive assessment to characterize placental dysfunction severity, as recommended by the American College of Obstetricians and Gynecologists 2.
After initial assessment, serial umbilical artery Doppler every 1-2 weeks guides subsequent management, according to the American College of Obstetricians and Gynecologists 2, 5.