The association between Mullerian anomalies and short-term pregnancy outcome

To determine the association between Mullerian anomalies (MuAs) and short-term perinatal outcome.

A retrospective cohort study, comparing pregnancy outcome in women with and without MuAs matched by age, number of fetuses and parity in a 1:2 ratio.

Among 243 women with MuAs, 156 (64.2%) had bicornuate uterus, 38 (15.6%) had septate uterus, 27 (11.1%) had unicornuate uterus and 22 (9.1%) had didelphic uterus. Compared to controls (n = 486), women with MuAs had higher rates of previous preterm deliveries (PTDs) (20.2 versus 5.9%, p < 0.001) and previous cesarean section (CS) (50.6% versus 12.5%, p < 0.001). Women with MuAs had higher rates of PTDs <37 weeks (25.1% versus 6.1%, p < 0.001) and <32 weeks (4.1% versus 0.6%, p = 0.001), preterm premature rupture of membranes (PPROM) (12.8% versus 2.7%, p < 0.001) and small for gestational age (SGA) infants (12.3 versus 6.8%, p = 0.01). There was higher rate of CS in the MuA group (82.3 versus 22.1%, p < 0.001), mainly due to higher rates of malpresentation and previous CS. In multivariate analysis, MuA was associated with SGA (2.04, 1.15-3.63), PTDs <37 weeks (3.72, 1.79-7.73), PTDs <32 weeks (7.40, 1.54-35.56), PPROM (6.31, 3.04-13.12), malpresentation (21.62, 12.49-37.45) and retained placenta (4.13, 1.73-9.86). No increased risk was observed in the rate of in-labor CS (0.52, 0.21-1.30, p = 0.16). When the rate of adverse outcomes was stratified according to MuAs subtypes, women with unicornuate uterus had the highest rate of breech presentation at delivery (55.6%) and women with didelphy uterine had the highest proportion of PTDs <37 weeks (40.9%).

Women with MuAs are at increased risk for adverse pregnancy outcome, mainly PTDs + and PPROM, SGA infants and CS due to malpresentation. However, the risk of in-labor CS is not increased compared to the general population.