DUCTUS VENOSUS VELOCITY WAVE-FORMS IN APPROPRIATE AND SMALL-FOR-GESTATIONAL-AGE FETUSES

The objective of this study was to evaluate differences in ductus veno sus velocity waveforms between appropriate and small for gestational a ge fetuses by using a new index based on the ratio between systolic an d atrial peak velocities. Ductus venosus velocity waveforms were cross -sectionally recorded in 164 appropriate for gestational age fetuses a t 16-42 weeks of gestation and in 97 small for gestational age fetuses free from structural and chromosomal abnormalities between 24-36 week s of gestation. Small for gestational age fetuses were divided accordi ng to the Doppler findings in arterial peripheral vessels: group A (n = 33), normal ratio between umbilical artery and middle cerebral arter y Pulsatility Indices; group B (n = 41), umbilical artery/middle cereb ral artery ratio > 95th centile but presence of end diastolic flow in umbilical artery; group C (n = 23), umbilical artery/middle cerebral a rtery ratio >95th centile and absence of end diastolic flow in umbilic al artery. Eighteen small for gestational age fetuses (10 from group B and 8 from group C) were also serially studied until delivery due to fetal distress. Ductus venosus velocity waveforms were recorded at the level of its origin from umbilical vein and the ratio between systoli c and atrial peak velocities (systolic/atrial ratio) calculated. In ap propriate for gestational age fetuses, systolic/atrial ratio values si gnificantly decrease with gestation. No significant differences were f ound in systolic/atrial ratio between appropriate for gestational age fetuses and group A small for gestational age fetuses while, after cor rection for gestational age, significantly higher values were found in group B (P less than or equal to 0.01) and group C (P less than or eq ual to 0.001) fetuses. Among these fetuses, those with systolic/atrial ratio above the 95th confidence interval showed a poorer perinatal ou tcome. No relationships were found between systolic/atrial ratio and P ulsatility Index values from fetal arterial peripheral vessels, while a positive relationship was found with the percentage reverse flow in inferior vena cava. In fetuses serially followed, the systoliciatrial ratio progressively increased approaching the onset of abnormal fetal heart rate patterns. The systolic/atrial ratio allows the evaluation o f ductus venosus hemodynamics in small for gestational age fetuses and this index may be useful in the monitoring of such fetuses.