Risk of postpartum hemorrhage according to the ultrasound measurement of the lower uterine segment before delivery of women with a prior cesarean delivery: secondary exploratory research of the Lower Uterine Segment Trial

The authors aimed to evaluate the relationship between antenatal lower uterine segment thickness and the risk of postpartum hemorrhage in women with a prior cesarean delivery who achieved a vaginal birth after cesarean. Their findings suggest that a thicker lower uterine segment is associated with a lower risk of atonic postpartum hemorrhage, while no protective effect was observed for hemorrhage due to abnormal placental separation, indicating different underlying mechanisms. These results are preliminary and warrant further investigation in larger studies.