Detection of the cervical gland area in threatened preterm labor using transvaginal sonography in the assessment of cervical maturation and the outcome of pregnancy

Objectives: To detect the cervical gland area in threatened preterm labor, and to determine its detection rate and relationship with cervical maturation and outcome of pregnancy in preterm labor. Methods: This was a mixed longitudinal and cross-sectional study involving 615 transvaginal scans performed to detect the cervical gland area and measure cervical length in 101 singleton pregnancies with threatened preterm labor. The patients were treated with intravenous administration of ritodrine chloride for regular uterine contractions at 16-35 weeks of gestation. 260 normal singleton pregnancies served as controls. Simultaneously conventional digital examination was used to assess the cervical maturation index. The detection rates of the cervical gland area, measurements of cervical length by sonography, and assessment of the cervical maturation index by digital examination in threatened preterm labor were compared with those of normal singleton pregnancies. In the threatened labor group, the outcome of pregnancy was assessed according to the sonographic absence or presence of the cervical gland area. Results: In the normal pregnancy group, the detection rate of the cervical gland area remained practically constant until the 31st week of pregnancy (97%), but substantially decreased thereafter (70.2% in gestational weeks 32-35). In the threatened preterm labor group, the detection rate of the cervical gland area was constantly lower (44.5%) and the cervical maturation index was higher (4.65 score) than in the normal pregnancy group (83.1% and 1.80 score, respectively). The outcome of pregnancy in the threatened preterm labor group was poorer in the subgroup with the absence of a cervical gland area than in the subgroup with the presence of a cervical gland area (duration of pregnancy 257.0 vs. 271.0 days, birth weight 2,597.2 vs. 2,990.0 g, and admission to delivery interval 38.8 vs. 60.8 days). Highly significant correlations were noted among the detection rates of a cervical gland area and cervical length, cervical maturation index, and outcome of pregnancy. Conclusions: This study demonstrates for the first time that the sonographic absence of the cervical gland area reflects cervical maturation and could be considered as a predictor of threatened preterm labor and a sign of poor outcome of pregnancy in this condition.