Reference values of focused assessment with sonography for obstetrics (FASO) in low-risk population

Objective: Hemorrhagic shock is a relatively common occurrence in the postpartum period. In our hospital, we performed abdominal ultrasonography using the focused assessment with sonography for obstetrics (FASO) technique (a modified version of FAST). The aim of the present study was to determine the reference values for the ultrasonographic findings to establish the criteria for the diagnosis of a postpartum hemorrhage and severe shock using the FASO. Methods: The present prospective cohort study included all postpartum women who vaginally delivered singleton infants. Abdominal ultrasonography was performed after delivery. The observation points of ultrasonography were as follows: (1) the diameter of the intrauterine cavity, (2) the pouch of Douglas, (3) Morison’s pouch, (4) between the spleen and kidney, and (5) the diameter of the inferior vena cava. Results: One hundred and eighty-two postpartum women were included in this study. The mean uterine cavity was 9.8 ± 7.3 mm. An echo-free space in the pouch of Douglas was observed in three cases, in one case in Morison’s pouch, and not observed between the spleen and kidney. A negative correlation was found between the volume of bleeding and IVCi (p = 0.0008, r²= −0.061) and IVCe (p < 0.0001, r²= −0.106). Conclusions: The present study establishes criteria that can be used to diagnose a postpartum hemorrhage or severe shock using the FASO.