ABSTRACT. Maximum flow velocity wave forms in the breathing movements (5). There is a significant reduction in ductus arteriosus were studied longitudinally in 40 fetuses ductal peak flow velocity during inspiration as compared with from 18 to 38 wk of gestation at 3-to 4-wk intervals. expiration, and this difference in peak flow velocity increases Median maternal age was 29 y (range 18-41 y), median exponentially with advancing gestational age, reflecting the deparity was 1 (range 0-6). All flow velocity wave forms were veloping pulmonary vascular bed (5). obtained using a mechanical sector scanner with a continTo our knowledge, a detailed analysis of normal fetal ductal uous Doppler system (carrier frequency 3.5 MHz). The wave forms has never been canied out in a longitudinal setting. flow velocity parameters studied were peak-systolic, peak-The objective of the present study was 2-fold: 1 ) to establish the diastolic, and time-averaged velocity and acceleration time. distribution of peak-systolic, peak-diastolic, and time-averaged There was considerable variability in measurements be-velocities as well as acceleration time in the fetal ductus arteriosus tween fetuses at any particular gestational age. An increase between 18 and 38 wk of pregnancy; and 2) to determine whether of ductal flow parameters with advancing gestational age there is fetal heart rate dependency for one or more of the was found. They showed no correlation with heart rate. aforementioned parameters within the physiologic fetal heart These results suggest that the normal second half of preg-rate range (i.e. 1 10-160 bpm) and, if so, to establish the relationnancy is characterized by a reduction in right ventricular ship between fetal period time (the reciprocal of heart rate) and afterload. This may be a result of decreased placental the parameter concerned. vascular resistance or increased pulmonary vascular flow. Acceleration time in ductal flow velocity wave forms was PATIENTS AND METHODS significantly higher than that observed in the pulmonary artery and ascending aorta, suggesting a lower afterload in A total of 40 women with normal singleton pregnancies conthe ductus arteriosus compared with the other two outflow sented to participate in the study. The study protocol was aptract vessels. (Pediatr Res 30: [487][488][489][490] 1991) proved by the Hospital Ethics Committee. Fetal ductal Doppler examinations were carried out at 3-to 4-wk intervals between Abbreviations 18 and 38 wk of gestation. The first examination was performed between 18 and 22 wk of gestation. PSI, prostaglandin synthetase inhibitorsNormal pregnancy was defined by a normal fetal biparietal diameter and birth weight between the 5th and 95th percentile according to Kloosterman's tables, corrected for maternal parity and fetal sex (6). The pregnancy duration was determined from ~h~ ductus arte,.josus is a large vessel that connects the pul-the last menstrual period and confirmed by ultrasonic measuremonary trunk with the descending aorta during fetal life. Thus, men...
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