Preliminary study on the effect of ultrasound on postpartum uterine involution and breast pain: a randomised controlled trial

Abstract

Objectives To evaluate the safety and efficacy of low-intensity focused ultrasound (LIFUS) therapy in promoting fundus descent and relieving postpartum breast pain compared with sham treatment. Methods A multicentre, randomised, sham-controlled, blinded trial was conducted. A total of 176 participants who had normal prenatal check-ups and met the inclusion and exclusion criteria were enrolled from three medical centres and subsequently randomised into the LIFUS or sham group. All participants provided three times treatment, LIFUS signal to the uterus and breast site through coupling gel, wherein a ultrasound signal output was absent in sham group. Fundal height measurement and breast pain score were performed after each treatment. The primary outcome was uterine involution, which was presented by measuring the fundal height of the uterus. The visual analogue scale (VAS) score, as a secondary outcome, was used to simultaneously assess breast pain and the correlation between breast pain and fundal height as the outcome. Results All participants were randomised into the LIFUS group (n = 88) or sham group (n = 88), of whom seven did not complete treatment. Overall, a statistically significant difference was noted in the rate and index of fundus descent after each treatment. The rate and index of fundus descent were more significant following the second (rate: 1.3 cm/d; index: 0.13, P < 0.001) and third (rate: 1.71 cm/d; index: 0.26, P < 0.001) treatments in the LIFUS group. VAS scores, which were based on the continuous variable for the baseline, first, second, and third treatments in the LIFUS (2.23, 1.16, 0.78, and 0.28 points, respectively) and sham groups (2.09, 1.64, 1.98, and 2.49 points, respectively), had a statistically significant difference between the two groups. Meanwhile, the differences in VAS score classification variables between the two groups were statistically significant. After the third treatment, a significant correlation was observed between the VAS score decrease and fundus descent rate; the more the VAS score decreased, the faster was the fundal decline rate in the LIFUS group. Conclusions LIFUS therapy is safe and effective, which contributes to accelerated uterine involution and relieved postpartum breast pain. The study has registered in the Chinese Clinical Trial Registry (ChiCTR2100049586) at 05/08/2021.