[Study of the cervix of normal pregnancy and threatened preterm delivery using transvaginal sonography].

OBJECTIVE

To observe the changes of cervix in women between 16 and 35 weeks of gestation using transvaginal ultrasound and to determine the value of the cervix length in predicting preterm delivery among the women with threatened preterm labor.

METHODS

Transvaginal sonography were performed in 154 normal single nulliparous pregnant women between 16 and 35 weeks of gestation and 58 women with threatened preterm labor but without premature rupture of membrane.

RESULTS

(1) There is no definitely change in either cervical length or internal diameter of cervix among the pregnant women over the studied period. There was also no funneling to be observed. The mean cervical length is (36 +/- 5) mm, and the mean cervical internal diameter is (4 +/- 1) mm. (2) Eleven preterm deliveries occurred among the 58 pregnancy women with threatened preterm labor. The cervical length by sonography of 11 preterm deliveries was (18 +/- 6) mm, and was significant shorter than the women without preterm deliveries whose mean cervical length was (32 +/- 6) mm (P < 0.001). The cervical length of women who delivered pretermly was totally <or= 26 mm. (3) A cervical length of 26 mm (x-2 s) as the cutoff to predict the preterm delivery among women with the threatened preterm labor has a 100% of sensitivity, 81% of specificity, 55% positive predictive value and a 100% of negative predictive value.

CONCLUSIONS

Cervical length by transvaginal sonography can be used to predict preterm delivery among the women with threatened preterm labor. Among women treated for preterm delivery, a cervical length of less than 26 mm indicated a high risk of preterm delivery, and intensive management is required.