Objective: To demonstrate that transvaginal ultrasound cervicometry in pregnant women with preterm labor is a predictor of preterm labor at the MINSA II - 2 Tarapoto Hospital, January - august 2016. Methodology: An observational, analytical, retrospective, cross-sectional study of the diagnostic test was performed; between January and August 2016, the sample consisted of 81 clinical records of pregnant women with preterm birth threat who met the selection criteria. Sensitivity and specificity (as validity parameters), positive and negative predictive value (as safety parameters) and the ROC curve with its area under the curve (for diagnostic accuracy) were used to know the predictive diagnostic capacity. Results: Comparing cervicometry values between 15 and 30 mm, the cut-off point of 25 mm has the best sensitivity (88,9%) and specificity (81,5%), and the positive predictive value is 70,...