Preterm birth and uterine fibroid necrosis: The clinical presentation illustrated in a case series.

Objective: Uterine fibroids increase the risk of preterm birth. The current study highlights uterine fibroid necrosis as a possible cause of (extreme) preterm birth.

Study Design: Retrospective cohort study in one Dutch academic hospital. Cases were selected from the 526 participants of the MyoFert study (Netherlands Trial Register, NL7990), which included patients who presented between 2004 and 2018 and were between the age of 18 and 45 years at the time of diagnosis of uterine fibroids. Of these participants, 414 women became pregnant. A retrospective chart review of the first pregnancies was performed. The main outcomes were (imminent) preterm birth and signs of fibroid necrosis on ultrasound. In women with signs of fibroid necrosis, the following data were collected systematically: fibroid characteristics, clinical presentation, pregnancy outcome, and postpartum period.

Results: In total, 66 women had a preterm birth (16 %, 66/414), of which 25 pregnancies ended between 16 and <24 weeks (38 %, 25/66) and 41 pregnancies ended between 24 and <37 weeks of gestation (62 %, 41/66). Of all women with preterm birth and available ultrasound images, 15 % (7/48) had fibroid necrosis at the time of labour. These seven patients, supplemented with three patients with fibroid necrosis during their first pregnancy and at least one episode of imminent preterm birth, are described in more detail. In these ten patients, the fibroids increased substantially in size during the first and second trimester, leading to severe abdominal pain in all patients and hospital admission in seven patients. Ultrasound examination of the fibroids showed heterogenic changes and focal transonic areas in the fibroid, which are characteristics that indicate fibroid necrosis. In four patients, myomectomy was performed and necrosis was confirmed histologically.

Conclusion: Fibroid necrosis during pregnancy is likely associated with (imminent) preterm birth. Clinicians are advised to structurally evaluate the myometrium in pregnancy, specifically in women presenting with abdominal pain in the second trimester.