Evaluation of a Patient in Suspected Preterm Labor

EVALUATION OF A PATIENT IN SUSPECTED PRETERM LABOR

Prompt evaluation is critical in the patient who describes symptoms and signs suggestive of preterm labor. Use of an external electronic fetal monitor (tocodynamometer) may help to quantify the frequency and duration of con-tractions. The status of the cervix should be determined, either by visualization with a speculum or by gentle digi-tal examination. Because digital examination may increase the risk of infection in the setting of PROM, speculum evaluation to assess cervical dilation and effacement should be performed first if there is suspicion of rupture of fetal membranes. Changes in cervical effacement and dilation on subsequent examinations are important in the evalua-tion of both the diagnosis of preterm labor, as well as the effectiveness of management. Subtle changes are often of greatclinical importance, so serial examinations by the same exam-iner are optimal, when this is possible.

Because urinary infections can predispose a patient to uterine contractions, a urinalysis and urine culture should be obtained. A vaginal/rectal culture should be obtained for group B streptococcus (GBS). Women with GBS bac-teruria are candidates for intrapartum antibiotic prophylaxis. When indicated by history or physical examination findings, cultures for Chlamydia and Neisseria gonorrhoeae should be obtained.

Ultrasound examination is useful in assessing the ges-tational age of the fetus, estimation of the amniotic fluid volume (spontaneous rupture of membranes with fluid loss may precede preterm labor and may be unrecognized by the patient), fetal presentation, and placental location, as well as the existence of fetal congenital anomalies. Patientsshould also be monitored for bleeding, as placental abruption and placenta previa may be associated with preterm labor.

Information concerning the length of the cervix can be obtained through ultrasound examination, although re-sults are not particularly helpful unless the gestational age is less than 26 weeks. Amniocentesismay be performed to as-sess for intra-amniotic infection. Either clinical or subclinicalinfection of the amniotic cavity (chorioamnionitis) is thought to be associated with preterm labor. Amniotic fluid can be evaluated for the presence of bacteria, white blood cells, lactate dehydrogenase, and glucose. Evidence of white cells in the amniotic fluid, decreased glucose or elevated lactate dehydrogenase may indicate infection.

The presence of bacteria in amniotic fluid is correlated not only with preterm labor but also with the subsequent devel-opment of infection. A high suspicion of intrauterine infec-tion should prompt delivery regardless of the gestational age. Tocolysis is not appropriate in the setting of intrauter-ine infection. At the time of amniocentesis, additional am-niotic fluid may be obtained for fetal pulmonary maturity studies, which could influence subsequent management.