The cost of the technology is high, mainly if the desire is mass measurements with a preventive aim; therefore, it is necessary to investigate the creation of an index that can establish manually and indirectly the values of the dimensions of the pelvic outlet, mainly the obstetric conjugate diameter, which is the most sensitive in the diagnosis of a narrow pelvis (Aller & Pages, 1999).
This study was conducted on adolescent girls aged 14 to 19 years residing in the urban parishes of the Distrito Metropolitano de Quito (DMQ), Ecuador, with the aim of determining the Anterior Pelvic Index (API) as a predictive estimator of the obstetric conjugate diameter to differentiate narrow and normal pelvises.
A single investigator recorded the weight, height and interspinous distance, and another measured the obstetric conjugate diameter measured by ultrasonography.
This result, like the value of the obstetric conjugate diameter, was used to construct a mathematical model, applying a simple linear regression to obtain a prediction value for the obstetric conjugate diameter by calculating coefficients of the linear regression line.
In order to determine the API, height and interspinous distance were used; in addition, obstetric conjugate diameter measured by ultrasonography was used to predict the true conjugate diameter.
The mean of the obstetric conjugate diameter was 11.05 cm (CI 95 % 11 to 11.1), with a standard error of the mean of 0.02, a variance of 0.12 and standard deviation of 0.4.
A Pearson correlation was used to establish the linear association between the API and the obstetric conjugate diameter measured by ultrasonography, obtaining an r value of 0.543 (p = 0.000).
The formula to predict the obstetric conjugate diameter, having the API as a predictor, is the following:
The aim of our study was to determine normal values for the anatomic conjugate diameter (ACD), the obstetric conjugate diameter (OCD), the conjugate diameter diagonal (DCD) and the interspinous distance (ISD) using reformatted CT in a Mexican population and determine whether there are significant differences in these parameters regarding age groups.
Association between obstetric conjugate diameter measured by transabdominal ultrasonography during pregnancy and the type of delivery.
Images of the pelvis by three-dimensional reconstruction of a CT scan where the measurement technique anatomic conjugate diameter (a), obstetric conjugate diameter (b) and conjugate diameter diagonal (c) is observed.
OCD= Obstetric conjugate diameter. DCD= Conjugate diameter Diagonal.