Validation of Sacral Rhomboid Diameters and Maternal Height in Antenatal Prediction of Contracted Pelvis in Primigravida

Abstract

Background: Contracted pelvis when not diagnosed on time before labour leads to obstetric mishaps in developing countries. Material and Methods: This prospective study aimed to assess the validity of sacral rhomboid diameter and maternal height (Ht) to predict contracted pelvis antenatally and to compare its individual efficacy with the combination models in antenatal prediction of the contracted pelvis. Results: In 250 uncomplicated primigravida at 37 weeks or beyond, Height and Michaelis sacral rhomboid vertical and transverse diameters (VD and TD) were measured. Post-delivery patients were divided into two groups- Normal delivery (Group1) and contracted pelvis(CP) (Group 2 including Lower Segment Caesarean Section (LSCS) for contracted pelvis and assisted vaginal delivery due to non-progress of labour). Analysis was done using Microsoft Excel and R studio (Open source analytical tool V 1.2.335), cross-tabulation, and Pearson chi-square test. In our study, we found that the Mean maternal height and mean rhomboid dimensions (VD and TD) were significantly (p value 0.000) smaller in the CP group. In univariate analysis, Maternal height≤1.422 (m), VD ≤9.5 (cm) and TD ≤9.5 (cm) showed PPV of 59.26%, 29.63%, and 56.67% respectively. Of all parameters, Maternal height≤1.422 (m) was the most significant factor in the prediction of contracted pelvis and it detected 16 out of 27 women at risk of CP. However, when combination models were produced, HT+TD was the best predictor model at 10th percentile cut-off values with the highest PPV and Accuracy (77.78% and 93.3% respectively) and it detected 14 out of 18 women at risk of CP. Conclusions: Smaller dimensions of the sacral rhomboid along with the maternal height are independent predictors of contracted pelvis. Transverse diameter of Michaelis (TD) along with maternal height at cut-off values enhanced the predictability of contracted pelvis and can be used as a promising and easily measurable screening parameter to detect the women at risk of Contracted pelvis antenatally. KEYWORDS: Sacral Rhomboid diameters, Contracted pelvis, Antenatal Prediction, Maternal Height, Primigravida.