THE DEVELOPMENT OF ABNORMAL HEART-RATE PATTERNS AFTER ABSENT END-DIASTOLIC VELOCITY IN UMBILICAL ARTERY - ANALYSIS OF RISK-FACTORS

OBJECTIVES: Our objectives were to evaluate the time interval elapsing between the occurrence of absent end-diastolic velocity in the umbilical artery and either the development abnormal fetal heart rate patterns or delivery and to establish the maternal and fetal factors that may affect this interval. STUDY DESIGN: Thirty-seven fetuses free of structural and chromosomal abnormalities in which the development of absent end-diastolic velocity in umbilical artery was evidenced by serial Doppler recordings were studied. At the first occurrence the following factors were considered: gestational age, presence of hypertension or preeclampsia, amniotic fluid index, severity of growth retardation, and 10 different Doppler indices calculated from extracardiac and intracardiac vascular districts. Actuarial statistical methods were applied, with the occurrence of antepartum late heart rate deceleration as the censoring variable. RESULTS: The interval between the first occurrence of absent end-diastolic velocity in umbilical artery and delivery ranged from 1 to 26 days. Indications for delivery were the development of antepartum late heart rate decelerations in 23 fetuses (62.1%) and different maternal or fetal complications in the remaining 14 fetuses. Multivariate analysis revealed that gestational age and the presence of hypertension and pulsations in umbilical vein were the dominant factors in determining the length of this time interval. CONCLUSION: The duration of the time interval between the occurrence of absent end-diastolic velocity in umbilical artery and abnormal heart rate pattern differs considerably among fetuses, and it is mainly determined by gestational age and presence of maternal hypertension and pulsations in umbilical vein.