Serial translabial sonographic measurement of cervical dimensions between 24 and 34 weeks' gestation in pregnant Thai women

Abstract

Objective: To assess serial changes of cervical dimensions in pregnant Thai women between 24 and 34 weeks' gestation by translabial sonography. Methods: A longitudinal study of cervical dimensions obtained by translabial sonography at 24, 28, 30, 32, and 34 weeks' gestation in 144 women was conducted. The gestational age at labor was recorded and women were defined as having preterm labor or term labor according to whether there was onset of true labor pain before or after 37 completed weeks, respectively. Cervical changes over time were analyzed by repeated ANOVA. The associations between cervical dimensions and gestational age, parity and prepregnancy body mass index were calculated by multiple linear regression analysis. Results: Cervical length decreased whereas cervical width increased as gestational age advanced. Cervical length and width in women with term labor, but only cervical length in women with preterm labor, changed significantly throughout the period of 24-34 weeks' gestation (P < 0.01). The cervix was significantly longer in parous women and in women with a body mass index of more than 26 kg/m2, but was shorter in women of advanced gestational age. The cervix was significantly wider in parous women and in those of advanced gestational age. Weekly crude rate, adjusted for parity and prepregnancy body mass index, of both cervical length shortening and cervical width widening was 0.4 mm in women with term labor. Women with preterm labor had cervical shortening of 0.5 mm per week. Conclusions: Gestational age, parity and prepregnancy body mass index are significantly associated with the dynamic changes of cervical length and width in Thai women. These factors should be considered when assessing normal values of cervical dimensions and for predicting the risk of preterm delivery.