Assessing cephalopelvic disproportion: back to the basics.

Dystocia, or abnormally slow progress in labor, can result from cephalopelvic disproportion (CPD), malposition of the fetal head as it enters the birth canal, or ineffective uterine propulsive forces. Cephalopelvic disproportion occurs when there is mismatch between the size of the fetal head and size of the maternal pelvis, resulting in "failure to progress" in labor for mechanical reasons. Untreated, the consequence is obstructed labor that can endanger the lives of both mother and fetus. Despite the use of imaging technology in an attempt to predict CPD, there is poor correlation between radiologic pelvimetry and the clinical outcome of labor. Clinical pelvimetry still has a place in obstetrics for predicting or confirming CPD, but without appropriate training and repeated practice of this clinical skill, it is in danger of becoming a lost art. For this review, a computerized search of the terms cephalopelvic disproportion, dystocia, pelvimetry, obstructed labor, and malposition was done using MEDLINE, PUBMED, SCOPUS, and CINAHL, and historical articles, texts, articles from indexed journals, and references cited in published works were also reviewed.