BACKGROUND AND PURPOSE: 

• Girault et al. (Am J Obstet Gynecol, 2018) assessed 
  • The association between uterine leiomyomas in pregnancy and preterm birth 
  • Whether any association remains following myomectomy 

METHODS: 

• Retrospective cohort study  
  • Women with singleton pregnancies delivering >22 weeks  
  • Women with a leiomyomatous uterus were compared to women with no myomas 
• Leiomyomatous uterus group consisted of either  
  • No history of myomectomy: ≥1 fibroid measuring ≥20 mm or multiple leiomyomas during pregnancy regardless of size | Seen on at least 1 obstetric ultrasound  | No history of myomectomy or 
  • History of myomectomy: Removal of ≥1 fibroid measuring ≥20 mm or multiple leiomyomas regardless of size, with or without persistent fibroids   

• Primary outcome: Preterm birth <37 weeks whatever the cause 
• Secondary outcomes  
  • Spontaneous preterm birth | Induced preterm birth 
• Characteristics possibly related to preterm birth were collected and assessed for confounding  

RESULTS: 

• 19,866 women were included in the study 
• 301 (1.5%) had a leiomyomatous uterus  
  • 154 without surgery | 147 with surgery  
• Leiomyomatous uterus was significantly associated with rate of preterm birth 
  • 12.0% in the leiomyomatous uterus group 
  • 8.4% in the nonleiomyomatous uterus group 
  • Adjusted odds ratio (OR) 2.5 (95% CI, 1.7–3.7) 
• Both surgical and non-surgical cases were significantly associated with preterm birth   
  • Without myomectomy: aOR 2.7 (95% CI, 1.6–4.6) 
  • With myomectomy: adjusted OR 2.3 (95% confidence interval, 1.3–3.9) 

CONCLUSION: 

• There is a 2.5-fold increased risk for preterm birth for women with fibroids  
• This association  
  • Persists even after myomectomy 
  • Regardless of spontaneous or induced  
• Possible mechanisms 
  • Women can still have fibroids present after surgery  
  • Surgery may alter myometrial muscle fibers and/or result in compromised dicidua/cellular hormonal function   
• Authors acknowledge limitations of their study, including the chance that women in the non-exposed group may have had fibroids, leading to inaccurate associations  
  • However, women who are at risk for preterm birth may often undergo multiple ultrasounds  

Learn more – Primary Sources: 

Leiomyomatous uterus and preterm birth: an exposed/unexposed monocentric cohort study

Related ObG Topics:

Are Fibroids Associated with Miscarriage?

What is the Risk of Myomectomy at the Time of Cesarean Section?

From Genetics to Soybeans: What are the Risk Factors for Uterine Fibroids?

High-Intensity Ultrasound for Fibroids – What are the Pregnancy Outcomes?