Intrapartum fetal head position I: comparison between transvaginal digital examination and transabdominal ultrasound assessment during the active stage of labor.

Objective: To test the null hypothesis that no correlation exists between transvaginal digital and the gold standard technique of transabdominal suprapubic ultrasound assessments of fetal head position during labor. A secondary objective was to compare the performance of attending physicians vs. senior residents in depicting fetal head position by transvaginal digital examination in comparison with ultrasound, respectively.

Methods: Consecutive patients in active labor at term with normal singleton cephalic-presenting fetuses were included. All participants had ruptured membranes, cervical dilation > or = 4 cm and fetal head at ischial spine station -2 or lower. Transvaginal sterile digital examinations were performed by either senior residents or attending physicians and followed immediately by transverse suprapubic transabdominal ultrasound assessments. Examiners were blinded to each other's findings. Power-analyses dictated number of subjects required. Statistical analyses included Chi-square, Cohen's Kappa test and logistic regression analysis. P < 0.05 was considered statistically significant.

Results: One hundred and two patients were studied (n = 102). In only 24% of patients (n = 24), transvaginal digital examinations were consistent with ultrasound assessments (P = 0.002, 95% confidence interval, 16-33). Logistic regression revealed that cervical effacement (P = 0.03) and ischial spine station (P = 0.01) significantly affected the accuracy of transvaginal digital examination. Parity, gestational age, combined spinal epidural anesthesia, cervical dilation, birth weight and examiner experience did not significantly affect accuracy of the examination. The accuracy of the transvaginal digital exams was increased to 47% (n = 48) (95% confidence interval, 37-57) when fetal head position at transvaginal digital examination was recorded as correct if reported within +/- 45 degrees of the ultrasound assessment. The rate of agreement between the two assessment methods for attending physicians vs. residents was 58% vs. 33%, respectively (P = 0.02) with the +/- 45 degrees analysis.

Conclusions: Using ultrasound assessment as the gold standard, our data demonstrate an overall high rate of error (76%) in transvaginal digital determination of fetal head position during active labor, consistent with the null hypothesis. Attending physicians exhibited an almost two-fold higher success rate in depicting correct fetal head position by physical examination vs. residents in the +/- 45 degrees analysis. Intrapartum ultrasound increases the accuracy of fetal head position assessment during active labor and may serve as an educational tool for physicians in training.