Effect of Ultrasound Therapy on Postpartum Uterine Involution: A Randomized Controlled Trial

Abstract Background Short-term poor uterine involution manifests as uterine contraction weakness. This is one of the important causes of postpartum hemorrhage and is a serious threat to the life and safety of the mother. To investigate whether low-intensity focused ultrasound (LIFUS) could shorten lochia duration, relieve postpartum, and accelerate uterine involution compared with the sham treatment. Methods A multicenter, concealed, randomized, blinded, and sham-controlled clinical trial was conducted at three medical centers with 176 subjects, using a parallel group design. Subjects were enrolled from October 2019 to September 2020 and followed up for 42 days. The subjects who had normal prenatal checkups and met the inclusion and exclusion criteria were randomly allocated into a LIFUS or a sham group with a random sequence generated by a computer. Patients in the LIFUS group were given usual care with LIFUS treatmet, in which a LIFUS signal was transmitted to the uterus site through coupling gel, or sham treatment, in which low-intensity ultrasound signal output was not present. The duration of lochia, measured by weekly telephonic follow-ups after discharge, was the primary outcome. The involution of the uterus, determined by measuring the height of the fundus of the uterus, was the secondary outcome. Results Of the 256 subjects screened for eligibility, 176 were enrolled and randomly divided into the LIFUS group (n = 88) or the sham group (n = 88). Data on the height of the uterine fundus was derived from all the patients and 696/704 (99%) measurements were taken. Overall, a statistically significant difference was noted in time to lochia termination (hazard ratio: 2.65; 95% confidence interval [CI]: 1.82–3.85; P < 0.05). The height of the fundus showed significant difference following the second (mean difference: −1.74; 95% CI: −1.23 to − 2.25; P < 0.05) and the third treatment session (mean difference: −3.26; 95% CI: −2.74 to − 3.78; P < 0.05) after delivery. None of the subjects had any adverse reactions, such as skin damage and allergy during treatment. Conclusions This study revealed that LIFUS therapy could be considered as safe and effective. Additionally, it contributed to uterine involution and reduced the duration of postpartum lochia.