What question did this study set out to answer?

To establish gestational-age-specific reference percentiles and develop a Z-score equation for the fetal atrioventricular time interval using pulsed Doppler echocardiography between 16 and 33+6 weeks of gestation.

April 30, 2025ULTRASONOGRAPHYOpen Access

Development of a Z-score equation for atrioventricular interval measurement by two-dimensional pulsed Doppler echocardiography in normal fetuses between 16 and 33+6 weeks of gestation

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Why the study?

Establishing a reference range for the fetal atrioventricular time interval throughout pregnancy is essential for early detection of potential abnormalities.

What is the normal reference range and Z-score equation for the atrioventricular interval measured by two-dimensional pulsed Doppler echocardiography in normal fetuses between 16 and 33+6 weeks of gestation?

Key Points

To establish gestational-age-specific reference percentiles and develop a Z-score equation for the fetal atrioventricular time interval using pulsed Doppler echocardiography between 16 and 33+6 weeks of gestation.
Conducted a multicenter, prospective, cross-sectional study between 2018 and 2022 in pregnant women without confounding maternal or fetal conditions.
Performed 1,309 two-dimensional pulsed Doppler echocardiographic examinations assessing left ventricular inflow and outflow, yielding an analyzed sample of 1,183 pregnant women.
Derived the standard reference equation for the fetal AV interval: Z-score = (AV interval measurement - 111.3) / 8.6.
Identified a very weak positive correlation between AV interval measurement and gestational age (r = 0.16, P < 0.001) and a weak negative correlation with fetal heart rate (r = -0.21, P < 0.001).

Structured PICO

Population

1,183 pregnant women with singleton pregnancies and live normal fetuses between 16 and 33+6 weeks of gestation. Mean maternal age 29.7 years, mean BMI 27.6 kg/m2. Excluded: fetuses with malformations, suspected arrhythmias, maternal obesity (BMI >35), chronic diseases, smoking, illicit drug use, and abnormal amniotic fluid index.

Intervention

Two-dimensional fetal echocardiography using pulsed Doppler to measure the atrioventricular (AV) interval (time between the onset of the mitral valve A wave and the onset of the aortic valve systolic flow).

Outcome

Z-score equation and specific percentiles for the atrioventricular (AV) time interval in normal fetuses between 16 and 33+6 weeks of gestation.surrogate

This study establishes a robust Z-score equation and percentile reference values for fetal AV interval measurements, facilitating the early detection of AV conduction abnormalities in high-risk pregnancies.

Limitations

AV interval was measured in a single plane (left ventricular inflow and outflow) without employing additional planes to obtain the spectral curve.
Not all fetal echocardiograms included more than one measurement per spectral curve.

Implication

May aid fetal AV-block surveillance in anti-Ro pregnancies; leaves open outcome validation before protocol change.

Abstract

PURPOSE: Fetal echocardiography is the primary diagnostic tool for assessing the atrioventricular (AV) time interval. Establishing a reference range for this parameter throughout pregnancy is essential for the early detection of potential abnormalities. The aim of this study was to develop a Z-score equation and establish specific percentiles for the AV time interval in normal fetuses between 16 and 33+6 weeks of gestation. METHODS: A multicenter, prospective, cross-sectional study was conducted between 2018 and 2022. A large sample of pregnant women meeting specific eligibility criteria was included, while cases with potential confounders were excluded. Two-dimensional echocardiography with pulsed Doppler techniques was employed, focusing on the left ventricular inflow and outflow. Data were rigorously analyzed with careful assessment of measurements and normalization procedures. RESULTS: In total, 1,309 echocardiograms were performed, and 1,183 pregnant women were included after applying the eligibility criteria. Detailed percentiles for each gestational age were determined, and a Z-score equation was formulated. A very weak correlation was observed between AV interval measurement and gestational age (r=0.16, P<0.001). In addition, the correlation between AV interval measurement and fetal heart rate was weak (r=-0.21, P<0.001). The Z-score for the AV interval measurement in milliseconds was derived as follows: Z-score=(AV interval measurement-111.3)/8.6. CONCLUSION: This study provides a reference range and Z-score equation for the AV interval, which may enhance the accuracy of monitoring fetuses at risk for developing atrioventricular block-especially in pregnant women with specific antibodies-thus facilitating earlier diagnosis and treatment.