OBJECTIVE: To evaluate the relationship of leiomyoma characteristics with perinatal outcomes. METHODS: A retrospective cohort study was conducted. Women whose pregnancy was complicated with leiomyoma were recruited, and pregnant women without leiomyomas were enrolled as a control group. Demographic data, leiomyoma ultrasound characteristics, and pregnancy outcomes were collected. Subsequently, antepartum, intrapartum, postpartum, and neonatal complications were analyzed. RESULTS: The overall rate of leiomyomas in pregnancy was 5.46% (4393/80510). Out of the 932 pregnancies studied, 632 were affected by leiomyoma. Women with leiomyomas exhibited significantly higher age, pre-pregnancy BMI, gravidity, and in vitro fertilization-embryo transfer rate. The occurrence of antepartum, intrapartum, and postpartum complications was influenced by different features of leiomyomas. Among leiomyoma with diameter of 9 cm or greater, cervical or submucous types were detrimental. In the multivariate linear regression analyses, a leiomyoma with diameter of at least 9 cm during pregnancy was independently associated with preterm birth, cesarean section, preterm premature rupture of membranes, and postpartum hemorrhage. CONCLUSION: The presence of leiomyoma of 9 cm or more increases the risk of antepartum, intrapartum, and postpartum complications
therefore, pre-conception myomectomy can be considered. For leiomyoma 7-9 cm, extensive discussions between patients and clinicians should be conducted. In women with leiomyomas smaller than 7 cm, the risk of obstetric complications is similar to that in women without leiomyomas, except for those with cervical or submucous leiomyomas.