Fetal breathing movements and the diagnosis of labor: a prospective analysis of 100 cases.

One hundred patients self-admitted to the hospital with a diagnosis of labor, were observed for up to 45 minutes with real-time ultrasonography to determine if the presence or absence of fetal breathing movements was helpful in separating false labor from true labor. Fetal breathing movements were not detected in 31 patients, and 30 of these delivered spontaneously within 48 hours; fetal breathing movements were present in 69 cases, and pregnancy continued for at least 48 hours in 56; of the remaining 13, labor occurred spontaneously within 48 hours in eight, whereas five had labor induced. Assessment of the cervix by Bishop score after ultrasound further improved diagnostic precision; none of 13 patients with a score greater than 9 exhibited fetal breathing movements, and all delivered within 48 hours. Gestational age did not influence outcome; 25 patients were preterm, and all 22 in whom fetal breathing movements were present continued for more than 48 hours. The results suggest that the absence of fetal breathing movements differentiates true labor from false labor.