If TVUS is declined by the patient or if the risk of TVUS is deemed too high (eg, placenta previa, suspected preterm premature rupture of membranes), transperineal US is a suitable alternative. In such instances, transperineal US would be indicated, noting the above caveats regarding CL in the early second trimester. Assessment of Gravid Cervix US Cervix Transvaginal TVUS is the reference standard of imaging modalities used for assessment of the gravid cervix. The transvaginal approach affords the shortest distance between transducer and cervix, and TVUS transducers typically offer higher frequency evaluation and greater detailed evaluation. The combination of these features allows for complete visualization of the cervix, including the internal os where changes increasing the risk of PTB first occur. Lastly, transvaginal imaging is a highly reproducible test. Several studies have demonstrated that identification of a short CL by TVUS decreases the rate of PTB by directing patients to appropriate interventions. In a randomized placebo-controlled study by Fonseca et al [6], women with a sonographically short cervix who received progesterone demonstrated a 44% reduction in the rate of PTB <34 weeks, as well as a 41% decrease in neonatal morbidity. A separate randomized placebo-controlled study confirmed the benefit of progesterone administration and found a 45% decrease in PTB <33 weeks and a 50% decrease in PTB <28 weeks [8]. Reduction in PTB rates was also observed in patients undergoing cervical pessary placement [7]. When compared with patients undergoing expectant management, pessary placement was associated with a 78% reduction of PTB <34 weeks. Lastly, short CL treated by cerclage has been found to decrease PTB. In a meta- analysis of 5 trials of high-risk patients with short CL, cerclage placement resulted in a 30% decrease in PTB <35 weeks with significantly decreased rates of PTB seen before 37, 32, 28, and 24 weeks [5].
Assessment of Gravid Cervix. If TVUS is declined by the patient or if the risk of TVUS is deemed too high (eg, placenta previa, suspected preterm premature rupture of membranes), transperineal US is a suitable alternative. In such instances, transperineal US would be indicated, noting the above caveats regarding CL in the early second trimester. Assessment of Gravid Cervix US Cervix Transvaginal TVUS is the reference standard of imaging modalities used for assessment of the gravid cervix. The transvaginal approach affords the shortest distance between transducer and cervix, and TVUS transducers typically offer higher frequency evaluation and greater detailed evaluation. The combination of these features allows for complete visualization of the cervix, including the internal os where changes increasing the risk of PTB first occur. Lastly, transvaginal imaging is a highly reproducible test. Several studies have demonstrated that identification of a short CL by TVUS decreases the rate of PTB by directing patients to appropriate interventions. In a randomized placebo-controlled study by Fonseca et al [6], women with a sonographically short cervix who received progesterone demonstrated a 44% reduction in the rate of PTB <34 weeks, as well as a 41% decrease in neonatal morbidity. A separate randomized placebo-controlled study confirmed the benefit of progesterone administration and found a 45% decrease in PTB <33 weeks and a 50% decrease in PTB <28 weeks [8]. Reduction in PTB rates was also observed in patients undergoing cervical pessary placement [7]. When compared with patients undergoing expectant management, pessary placement was associated with a 78% reduction of PTB <34 weeks. Lastly, short CL treated by cerclage has been found to decrease PTB. In a meta- analysis of 5 trials of high-risk patients with short CL, cerclage placement resulted in a 30% decrease in PTB <35 weeks with significantly decreased rates of PTB seen before 37, 32, 28, and 24 weeks [5].