Measured Versus Hemoglobin-Calculated Postpartum Blood Loss in Waterbirth

During a waterbirth, blood lost in the pool between the birth of the baby and the mother's exit from the water cannot be collected or measured. At the participating centers, blood loss is measured with a graduated collector bag that is positioned only after the woman leaves the pool, for the delivery of the placenta. The blood loss recorded after a waterbirth may therefore be lower than the true loss. The goal of this observational study, conducted in two Italian hospitals, is to learn whether measured blood loss underestimates true blood loss more after waterbirth than after birth on land. The main question it aims to answer is: Is the difference between blood loss calculated from the drop in hemoglobin and blood loss measured in the collector bag larger in women who give birth in water than in women who give birth on land without water immersion? Researchers will compare three groups of low-risk women with a singleton pregnancy at term: women who give birth in water, women who use water immersion during labor but give birth out of water, and women who do not use water immersion. No intervention is assigned by the study: each woman is classified according to what actually happened during her labor and birth. Data are taken from the clinical record and include hemoglobin at admission in labor and after birth, measured blood loss, and the timing of events in the pool and during the third stage of labor.

Inclusion Criteria: * Singleton pregnancy * Cephalic presentation * Gestational age from 37 weeks 0 days to 41 weeks 6 days * Low-risk pregnancy, eligible for water immersion according to the protocol of the center * Hemoglobin measured at admission in labor * Vaginal birth; for Group C, spontaneous vaginal birth with no water immersion at any time in labor Exclusion Criteria: * Blood transfusion before the postpartum blood sample * Known coagulopathy * Cesarean delivery * Operative vaginal delivery (Group C)