The Risk of Preterm Births Among Pregnant Women With Adenomyosis

Objectives Few studies have examined the effect of adenomyosis on pregnancy outcomes. We aimed to evaluate the risk of preterm birth and low birth weight in women with adenomyosis diagnosed during pregnancy. Methods A computerized ultrasonography database was used to identify singleton pregnant women with adenomyosis in the first trimester from January 2010 to December 2011. Only cases with a known pregnancy outcome were included. We reviewed the medical records and analyzed pregnancy outcomes according to the presence of adenomyosis and conception method. Results Among 11,173 singleton pregnant women, adenomyosis was detected in 88 (0.8%), and 8316 pregnant women (including 72 with adenomyosis) were included. The adenomyosis group was associated with significantly higher rates of preterm birth and low birth weight than the non‐adenomyosis group (12.5% versus 4.1%; P < .001; 13.9% versus 3.1%; P < .001, respectively). In a subgroup analysis according to the conception method, incidences of preterm birth and low birth weight were not different in the non‐adenomyosis group. However, the risks of preterm birth and low birth weight in the adenomyosis group were significantly higher in pregnant women who conceived by assisted reproductive technologies than in women who conceived naturally (28.0% versus 4.3%; P < .01; 28.0% versus 6.4%; P < .05, respectively). Conclusions Ultrasonographic findings suggesting adenomyosis in early pregnancy were associated with increased risks of preterm delivery and low birth weight in women who conceived with the use of assisted reproductive technologies but not in women who conceived spontaneously.