The Anterior Pelvic Index (API) in the Classification of the Female Pelvis and Prediction of Fetopelvic Disproportion

Tweet about this on TwitterShare on FacebookEmail this to someoneShare on Google+

Marco Guerrero-Figueroa; Juan Ocampo; Marcia Zapata; Nathaly Rosales; José Guevara; Alejandra Calero; Paola Iñiguez; Bryan Cobeña & Alejandro Basantes


Measurements of the upper strait of the pelvis can be calculated using the Anterior Pelvic Index. The objective of the study was to determine the external validity and cut-off point of the API, to classify narrow pelvises from normal ones. We selected 214 women from 15 to 55 years old, 171 had vaginal delivery and 43 by caesarean section by feto-pelvic disproportion (FPD) of maternal origin, in whom the API was calculated, of which its mean difference was established with an alpha error of <0.05. Maximum values of sensitivity and specificity, ROC curve and Youden index were determined. The student's t gave a p-value =0.000 of the mean difference between the women who had vaginal delivery and those who had cesarean section by FPD of maternal origin; the value of the area under the ROC curve was 0.758 (CI 95% 0.695 – 0.814) with a p-value=0.0001. Maximum sensitivity was 74.42 % (CI 95%: 58.8 % to 86.5 %) and maximum specificity was 73.10 % (CI 95%: 65.8 % to 79.6 %), produced a Youden index of 0.475 (CI 95% 0.283 – 0.590) which is associated with the 15.44 (CI 95% 14.19 – 15.83) of the API scale. The API is a good tool for predicting women with suspected narrow pelvis and allows its classification into three types of pelvises: an API value of more than 15.83 would indicate pelvis suitable for vaginal delivery; an API value between 14.19 and 15.83 would be suspected of pelvic narrowness; an API value less than 14.19 would confirm a narrow pelvis.

KEY WORDS: Pelvimetry; Anterior pelvic index; Fetopelvic disproportion.

How to cite this article

GUERRERO-FIGUEROA, M.; OCAMPO, J.; ZAPATA, M.; ROSALES, N.; GUEVARA, J.; CALERO, A.; IÑIGUEZ, P.; COBEÑA, B. & BASANTES, A. The Anterior Pelvic Index (API) in the classification of the female pelvis and prediction of fetopelvic disproportion. Int. J. Morphol., 41(5):1461-1466, 2023.