[Diagnosis and prognosis of preterm labor: physical examination and ultrasonography]

Abstract

Diagnosis. Preterm labor is defined by cervical changes associated with regular painful uterine contractions (UC) between 22 and 36 weeks + 6 days. Tocometry does not improve diagnosis or prognosis, despite the identification of more UC (NP 4). Electromyography and cervical distensibility (cervicotonometer) are promising techniques but are still in the research field. Clinical markers for prognosis. Clinical markers associated with clinical cervical examination tested in scoring systems are not validated and can't be recommended in clinical practise (NP 4). Ultrasonographic examination of the cervix. Technical evaluation of ultrasonographic examination of the cervix is satisfactory (NP 3); the transvaginal technical have to be used (NP 3). This method has a better accuracy and reproducibility than clinical examination provided a good apprenticeship (NP 3). Three ultrasound abnormal criteria are defined: a short length, a large internal cervical os and the presence of a funnel in the cervical canal. The best cut-off of cervical length to predict preterm delivery lies between 18 and 30 mm (NP 3). The choice of the cutt-off level depends on the prectitioner: high sensitivity but with many false-positives (cut-off close to 30 mm) or lower sensitivity with few false-positives (close to 20 mm). Cervical length seems to be more accurate that internal os or presence of a funnel which should be used with caution in clinical decisions (NP 3). There is no comparative study about the use of ultrasonographic examination of the cervix in women with preterm labor to evaluate benefits and adverse effects in clinical practice. However, ultrasonographic examination of the cervix supply a progress identifying women at risk of preterm delivery and this technique has a better predictive value than clinical cervical examination (NP 3). It seems reasonable to recommend utilisation of ultrasonographic examination of the cervic in preterm labor. It would not seem reasonable to replace the vaginal examination by ultrasonography. Ultrasonography could be used in association with clinical examination or in a second time if clinical examination is doubtful (NP 3). For these women, ultrasonography could reduce the number of hospitalizations, limiting treatment for some and, for others, increasing intensive interventions such as tocolysis, in utero transfer or corticsteroid treatment.