Reference Ranges for the Fetal Myocardial Performance Index Assessed by Conventional Doppler Between 11 + 0 and 14 + 0 Weeks of Gestation.

BACKGROUND: Early fetal cardiac evaluation during the first trimester has become increasingly feasible due to advancements in ultrasound technology. The myocardial performance index (Tei index) is a Doppler-derived parameter that assesses combined systolic and diastolic cardiac function. OBJECTIVE: To assess fetal cardiocirculatory status using two-dimensional and Doppler ultrasound during routine first-trimester evaluation and to establish reference ranges for the Tei index between 11 + 0 and 14 + 0 weeks of gestation. STUDY DESIGN: This cross-sectional study included 470 healthy singleton fetuses evaluated with two-dimensional and Doppler ultrasound. The Tei index was measured for both ventricles following a standardized protocol. RESULTS: The mean Tei index was 0.47 (±0.08) for the right ventricle and 0.46 (±0.08) for the left, with a statistically significant difference (p = 0.032) that was not clinically relevant. The index followed a log-normal distribution. No significant correlation was observed with crown-rump length, while a weak but statistically significant correlation was observed between the Tei index and left-ventricular heart rate. CONCLUSION: The Tei index can be measured between 11 and 14 weeks of gestation using noninvasive ultrasound techniques. This study provides reference data for both ventricles in a Latin American cohort and contributes to the limited literature on first-trimester fetal cardiac functional assessment. Further prospective studies are needed before routine clinical implementation can be recommended.