Study of Placental Bed of Growth Restricted Fetuses: Correlation of Doppler Velocimetries of Uterine and Umbilical Arteries With Placental Pathology

When indicated, a conservative management plan of IUGR was undertaken according to a defined protocol including antenatal visits, ultrasound surveillance. The frequency of fetal surveillance was assessed at each visit according to the maternal and fetal conditions.

Doppler studies were performed within the last week before delivery using a 3.5-Mhz transducer, color-flow mapping, and a 50-Hz high-pass filter; all measurements were performed with the mothers in a semi recumbent position. Color-flow imaging was used to visualize the ascending branch of the uterine arteries. Pulsed Doppler velocimetry was performed with a sample volume of 5 mm.

A minimum of three separate recordings was taken for each examination. The wave contour of the uterine arteries was studied for the presence of a diastolic notch from which the systolic/end-diastolic (S/ D) ratio was calculated. Abnormal uterine velocimetry was defined as an average of (left and right) S/ D ratio and by the bilateral presence of diastolic notching. Umbilical artery waveform was measured from free-floating loop of cord during fetal quiescence. The pulsatility index (PI) (maximum velocity - minimum velocity/ mean velocity) was calculated and the average of three measurements was used. An abnormal umbilical artery PI was defined as standard deviations above the mean for gestational age based reference standards (Chitty and Altman, 1999).

The results of Umbilical artery (UA) Doppler velocimetry were categorized as normal (end-diastolic velocity <90th percentile of our reference curve), increased (end-diastolic velocity ≥90th percentile), absent, and reversed (Madazil R et al., 2002) Patients were admitted for close surveillance in the case of worsening of maternal or fetal conditions (e.g. absent or reversed UA blood flow, and severe preeclampsia). Preeclampsia was defined according to standard criteria (Arduini D et al, 2002).

Tissue samples The general shapes of placentas were assessed. The collected placentas were weighed by trimming the membranes and umbilical cord. Then the diameters and thickness of placentas were noted. The position of insertion of umbilical cord on the fetal surface of placenta was observed. Transverse cuts were made through the maternal surface at a distance of 1-2 cm in bread loaf manner and examined for the pale areas. All placentas were immersed in 10% formalin overnight and examined on the next day. For each placenta, blocks containing cord, membrane and full thickness of villous tissue were prepared. Whole thickness villous tissue blocks were obtained from three zones, i)central zone ii) peripheral zone and iii) intermediate zone between the first two zones, so as to include all areas of placenta.