Increased risk of preterm births among women with uterine leiomyoma: a nationwide population-based study

Using a 3-year nationwide population-based database, this study examines the risk of adverse pregnancy outcomes [lower birthweight, preterm gestation and babies small for gestational age (SGA)] in pregnant women with uterine leiomyoma. This study linked two data sets: Taiwan's birth certificate registry and its National Health Insurance Research Data set. A total of 5627 mothers with uterine leiomyoma and 28 135 unaffected mothers were included for analysis. After adjusting for mother and infant characteristics and monthly family income, log-binominal regression and multivariate regression analyses were conducted to examine the risks of preterm birth, SGA and lower birthweight among mothers with uterine leiomyoma and unaffected mothers. Women with uterine leiomyoma had a significantly higher percentage of preterm births (10.98 versus 7.78%, P < 0.001) and SGA infants (19.00 versus 17.28%, P = 0.002) than unaffected mothers. The mean birthweights for mothers with and without uterine leiomyoma were 3083 and 3172 g, respectively (P < 0.001). Log-binominal regression models show that the adjusted risk ratios of preterm births and SGA infants for mothers with uterine leiomyoma were 1.32 (95% CI 1.19-1.46) and 1.16 (95% CI 1.08-1.26), respectively, compared with unaffected mothers. After finally adjusting for gestational age and other covariates, a multivariate regression analysis revealed that women with uterine leiomyoma had, on average, a 14.7 g lower birthweight than unaffected mothers (P = 0.022). We concluded that after adjusting for potential confounders, women with uterine leiomyoma experience a small yet significant increased risk of preterm and SGA infants. We suggest that clinicians intensively monitor women with uterine leiomyoma during pregnancy.