Relationship between a uterine fibroid diagnosis and the risk of adverse obstetrical outcomes: a cohort study

OBJECTIVE: The aim was to investigate the association between clinically significant uterine fibroids and preterm birth, caesarean section (CS), postpartum haemorrhage (PPH), placental abruption, intrauterine growth restriction (IUGR) and uterine rupture. METHODS, PARTICIPANTS AND SETTING: A historical cohort study based on data from the Danish National Birth Cohort, the Danish National Patient Registry and the Danish National Birth Registry (DNBR). The final study population consisted of 92 696 pregnancies and was divided into four groups for comparison. Group 1: pregnancies of women without a fibroid diagnosis code or fibroid operation code; group 2: pregnancies of women with a fibroid diagnosis code before pregnancy, during pregnancy or up to 1 year after delivery, and no fibroid operation code before pregnancy; group 3: pregnancies of women with a fibroid diagnosis code given more than 1 year after delivery; and group 4: pregnancies of women with a fibroid operation code given before pregnancy. RESULTS: A diagnosis of fibroids before pregnancy yielded an increased risk of preterm birth (gestational age (GA) ≤37 weeks) (OR 2.27 (1.30─3.96)) and extreme preterm birth (GA 22+0─27+6 weeks, OR 20.09 (8.04─50.22)). The risk of CS was increased (OR 1.83 (1.23─2.72)) for women with a fibroid diagnosis code given before pregnancy; significantly increased risk of elective CS (OR 1.92 (1.11─3.32)), but not acute CS (OR 1.54 (0.94─2.52)). The risks of PPH, placental abruption or IUGR were not increased in any of the groups. CONCLUSION: We found a strong association between clinically significant uterine fibroids and preterm birth, and an association between clinically significant uterine fibroids and CS. In contrast, no association between clinically significant uterine fibroids and PPH, placental abruption or IUGR was seen.