Maternal postural challenge as a functional test for cervical incompetence.

We studied the effect of an upright maternal position on the cervix. Of 41 high risk patients (17 to 33 weeks' gestational age), 14 of 16 who had a greater than 33% decrease in cervical length in the upright position compared to supine position delivered their infants prematurely, compared to 1 of 25 patients who had a decrease of less than 33% (P < 0.0005). No change in the cervical length was noted in 24 low-risk patients, all of whom were delivered at term. When the finding of a cervical length of less than 2 cm was combined with a postural change, the sensitivity for prediction of preterm delivery was 100%. We conclude that for patients at high risk for incompetent cervix, maternal posture-related cervical shortening can assist in predicting those who will undergo premature delivery.