Change of uterine leiomyoma size during pregnancy and the influencing factors: A cohort study

Objective To evaluate the changes of uterine leiomyoma size during pregnancy and determine the factors influencing it. Methods A prospective study was conducted from June 2016 to June 2018. Women with pregnancies complicated by leiomyoma were recruited. Ultrasound examinations were conducted to measure the size of leiomyoma during 6-7, 11-14, 22-24, 28-34 weeks of pregnancy and before delivery. The clinical characteristics and delivery details of the pregnant women were collected. Changes in leiomyoma size during different gestation periods and the influencing factors were analyzed. Results Leiomyoma size commonly increased before 22-24 weeks of pregnancy and the fastest growth occurred before 11-14 weeks. From 22-24 weeks to the date of delivery, the size of leiomyoma remained unchanged. The initial size of the leiomyoma showed negative correlation with the changes in leiomyoma diameters during pregnancy. Pre-pregnancy body mass index, fetus number, leiomyoma location, and parity were positively correlated with the size changes in leiomyoma from 22-24 to 28-34 weeks of pregnancy. Conclusion Before 22-24 weeks of pregnancy, the size of the leiomyoma was gestation-dependent, which increases with gestational weeks. The fastest growth rate was before 11-14 weeks. The growth of leiomyoma is affected by multiple factors, and different factors can play different roles during different periods of the pregnancy.