Uterine fibroids raise risks for adverse pregnancy, obstetric outcomes

Key takeaways:

• Uterine fibroids raise adverse pregnancy and obstetric outcomes risks including preterm and cesarean birth.
• Fibroid size was tied to higher breech presentation, postpartum hemorrhage and placenta previa risks.

Uterine fibroids increase risks for adverse pregnancy and obstetric outcomes with size, not number, tied to breech presentation, postpartum hemorrhage and placenta previa risks, according to a meta-analysis.

“Several studies have assessed the effects of uterine fibroids on pregnancy and obstetric outcomes,” Hong Li, MD, from the department of cardiology at the Shengjing Hospital of China Medical University, and colleagues wrote in BMC Pregnancy and Childbirth. “However, there are many inconsistencies in their findings on the relationships between fibroids and cesarean delivery, preterm delivery, breech presentation, placenta previa, preterm premature rupture of membrane, postpartum hemorrhage and intrauterine growth retardation with some investigations suggesting associations between fibroids and these complications and others reporting no elevated risks linked to the presence of fibroids.”

Li and colleagues searched PubMed, Embase, Web of Science, ClinicalTrials.gov, China National Knowledge Infrastructure and SinoMed databases and identified 24 studies with 237,509 participants. All studies evaluated uterine fibroid influence on adverse pregnancy outcomes.

In pooled data, uterine fibroids increased risks for the following adverse pregnancy and obstetric outcomes:

• preterm birth (RR = 1.72; 95% CI, 1.41-2.1);
• cesarean birth (RR = 1.95; 95% CI, 1.67-2.28);
• placenta previa (RR = 2.99; 95% CI, 2.06-4.35);
• miscarriage (RR = 4.51; 95% CI, 2.8-7.26);
• preterm premature rupture of membranes (RR = 1.37; 95% CI, 1.09-1.72);
• placental abruption (RR = 1.85; 95% CI, 1.48-2.32);
• postpartum hemorrhage (RR = 3.52; 95% CI, 2.16-5.73);
• fetal distress (RR = 3.61; 95% CI, 2.08-6.27);
• malposition (RR = 2.54; 95% CI, 1.75-3.69);
• intrauterine fetal death (RR = 2.34; 95% CI, 1.42-3.84);
• low birth weight (RR = 1.72; 95% CI, 1.03-2.85);
• breech presentation (RR = 2.26; 95% CI, 1.56-3.29); and
• preeclampsia (RR = 1.48; 95% CI, 1.1-2).

However, when adjusting for potential factors, uterine fibroid presence elevated risks only for preterm birth, cesarean birth, placenta previa, placental abruption, postpartum hemorrhage, intrauterine fetal death, breech presentation and preeclampsia.

In the subgroup analysis, larger fibroids were associated with higher risks for breech presentation (RR = 1.5; 95% CI, 1.03-2.19; P = .036), postpartum hemorrhage (RR = 5.04; 95% CI, 2.12-12.01; P < .001) and placenta previa (RR = 1.62; 95% CI, 1.16-2.25; P = .004) compared with smaller uterine fibroids. Having multiple fibroids was not associated with increased risks for breech presentation, placental abruption, cesarean birth, postpartum hemorrhage, placenta previa, preterm premature rupture of membranes, preterm birth and intrauterine growth restriction.

In addition, only maternal age influenced the relationship between fibroids and preterm birth (P = .012) while BMI influenced the relationship between fibroids and intrauterine fetal death (P = .04).

“There are very few studies on the associations between fibroid size and number on adverse outcomes,” the researchers wrote. “Our results provide valuable information for the identification of the risks of breech presentation, postpartum hemorrhage and placenta previa.”