Sagittal suture overlap in cephalopelvic disproportion: blinded and non-participant assessment.

OBJECTIVE: To determine the role of assessment of overlap of fetal skull bones (molding) in intrapartum prediction of cephalopelvic disproportion (CPD).

DESIGN: Prospective cross-sectional study.

SETTING: South African high-risk obstetric unit that receives referrals from other facilities.

POPULATION: Women of at least 37 weeks' gestation in the active phase of labor, with singleton vertex presentations and live fetuses, and without previous cesarean sections.

METHOD: The researcher was blinded to parity and previous clinical information on the women, and not involved in their obstetric care. The researcher performed clinical assessments, including estimation of level of head, cervical dilatation, head flexion, position, overlap of fetal skull bones, caput succedaneum and asynclitism. A single assessment was done on each woman.

MAIN OUTCOME MEASURE: CPD, defined as cesarean section for poor progress in labor.

RESULTS: The author examined 504 women, and CPD occurred in 113 (22.4%). In multivariate logistic regression analysis, sagittal suture overlap was independently associated with CPD. Other factors associated were maternal height, duration of labor, birth weight, and the interaction between caput succedaneum and cervical dilatation at the time of examination. Lambdoid suture overlap was not significantly associated with CPD, and could be determined in only 66.5% of examinations because of frequent head deflexion.

CONCLUSION: Assessment of sagittal suture overlap, but not lambdoid suture overlap, is useful for prediction of CPD. Knowledge of sagittal suture overlap may assist in decisions on clinical management where there is poor progress in a trial of labor.