[Correlation between the myometrial thickness in the second trimester and preterm delivery in a prospective study]

To investigate the relationship between preterm delivery and anterior myometrial (MA) thickness measured by ultrasound in the second trimester.

The general information and pregnancy outcome of singleton pregnant women who had antenatal visit in the Hunan Provincial People's Hospital between Oct 2010 and Sep 2013 were collected prospectively. The MA thickness was measured at 20-27(+6) gestational weeks. The cases were divided into preterm delivery group and term delivery group.

(1) A total of 1 031 pregnant women were recruited in this study. 147 pregnant women were in the preterm delivery group (14.26%, 147/1 031) and 884 women were in the term delivery group (85.74% , 884/1 031). The gestation age at delivery of the preterm delivery group was significantly earlier than the term delivery group [(34.57 ± 2.39) vs (39.23 ± 0.92) weeks, P < 0.05]. No significant difference was observed in the age, gravidity, parity, history of preterm delivery, cesarean delivery rate and gestational age at the time of MA measurement between the two groups (P > 0.05). The incidence of premature rupture of membrane (PROM) in the preterm delivery group and in the term delivery group were 49.0% (72/147) and 15.8% (140/884), respectively, with statistically significant difference (P < 0.01). (2) The mean value of MA thickness in the term delivery group was (5.49 ± 1.39) mm, while in the preterm delivery group it was (5.60 ± 0.87) mm. There was no statistically significant difference between the two groups(P > 0.05). The mean value of MA thickness in the spontaneous preterm delivery group was(5.15 ± 0.75) mm, and was (5.61 ± 1.38 ) mm in the term delivery group, with statistically significant difference (P < 0.01). The mean value of MA thickness in the preterm premature rupture of membrane (PPROM) cases was( 5.96 ± 0.78 ) mm, and in term delivery group with PROM it was (5.38 ± 1.12) mm. The difference between the two groups were statistically significant (P < 0.01). (3) Among the 1 031 pregnant women, 212 women had PROM, with the mean value of MA thickness of (5.67 ± 1.32) mm. For those who did not have PROM, the mean value of MA thickness was (5.56 ± 1.10) mm. There was no statistically significant difference between the two groups(P > 0.05). No correlation was found among PROM and MA thickness(r = 0.058, P > 0.05). However, in the preterm delivery group, the mean value of MA in PPROM was significantly thicker than the spontaneous preterm delivery cases (P < 0.01). There was a positive correlation between the MA thickness and PPROM (r = 0.457, P < 0.01).

The MA thickness had some correlation with spontaneous preterm delivery and PPROM, while the MA thickness should not be considered as an independent factor of preterm delivery.