Objectives: To measure Doppler flow resistance indices in the uterine arteries, and to observe when the early diastolic notches appear during the normal puerperium.
Methods: Some 45 women took part in this prospective longitudinal study after normal, vaginal delivery. Ultrasound examinations were scheduled for days 1, 3, 7, 14, 28 and 56 postpartum. A transabdominal probe was used during the first two postpartum weeks, and a transvaginal probe for the later examinations. The pulsatility (PI) and resistance (RI) indices in the uterine arteries were measured, and the presence or absence of early diastolic notches was recorded.
Results: Compared to day one, the resistance indices did not change markedly until day 28 postpartum. The mean PI was 1.23 at day 1, 1.22 at day 3, 1.22 at day 7, 1.33 at day 14, 1.81 at day 28, and 2.25 at day 56. The mean RI was 0.65 at day 1, 0.65 at day 3, 0.66 at day 7, 0.65 at day 14, 0.77 at day 28, and 0.84 at day 56. The presence of at least 1 uterine artery notch was found in 13.3% of the women at day 1, and in 90.6% at day 56 postpartum. Bilateral notches were recorded in 6.7% of the women at day 1, and in 84.4% at day 56 postpartum.
Conclusion: Reference values of the resistance indices from uncomplicated puerperium are needed when the diagnostic efficacy of Doppler ultrasound for pathological conditions is to be tested. This study confirms that the time needed for the vascular physiology to revert from a pregnant to a non-pregnant state appears to be longer than previously assumed.