FETAL ATRIOVENTRICULAR FLOW-VELOCITY WAVE-FORMS AND THEIR RELATION TOARTERIAL AND VENOUS FLOW-VELOCITY WAVE-FORMS AT 8 TO 20 WEEKS OF GESTATION

Background Doppler ultrasonography was used to determine the nature an d gestational age-related changes of human fetal AV flow-velocity wave forms and to establish their relationship with arterial impedance inde xes and venous now velocities in normal human fetuses between 8 and 20 weeks of gestation. Methods and Results Flow-velocity waveform record ings were attempted in 318 singleton pregnancies. After the exclusion criteria were applied, data on 214 women were available for further an alysis. Differentiation between E wave and A wave became Possible at 9 weeks, whereas distinction between transmitral and transtricuspid val ve flow velocities was first achieved at 10 to 11 weeks. A statistical ly significant nonlinear gestational age-dependent increase was establ ished for all AV waveform parameters, which became linear when related to logarithmically estimated fetal crown-to-rump length. Transtricusp id valve flow velocities were significantly higher than transmitral va lve flow velocities. Transmitral valve time-averaged flow velocities w ere positively correlated with peak diastolic velocities and time-velo city integral of late-diastolic reverse flow in the inferior vena cava . No correlation existed between AV time-averaged velocities and arter ial impedance indexes. Conclusions Monophasic AV flow-velocity wavefor ms can be recorded as early as 8 weeks of gestation and become biphasi c as early as 8 weeks. They demonstrate a linear increase relative to logarithmically estimated fetal crown-to-rump length, suggesting that fetal growth-related increase in volume flow plays a role in this velo city rise. Transtricuspid valve A-wave and E-wave velocities suggest r ight ventricular predominance as early as the late first trimester of pregnancy. AV flow velocities are not related to arterial downstream i mpedance.