Perinatal death and morbidity occur with cephalopelvic disproportion (CPD) as a consequence of the complications of obstructed labor. It is unclear whether overlap of fetal skull bones (molding) is a sign of normal labor, or is associated with and predictive of CPD. CPD is common in sub-Saharan Africans, who are considered to be at greater risk for CPD than Caucasians. A previous prospective study in the 1970s involving African women showed that overlap of skull bones at the sagittal suture and to a lesser degree at the lambdoid suture were associated with CPD and could be predictive. However, these findings were questioned for possible bias because of the absence of investigator blinding. In addition, the study lacked statistical analysis to adjust for confounding.
In this prospective blinded cross-sectional study, the authors examined 505 women of at least 37 weeks’ gestation in the active phase of labor with singleton live fetuses and vertex presentations, and no history of cesarean delivery. The authors defined CPD as cesarean section for poor progress in labor in the presence of adequate uterine activity; CPD occurred in 113 of the 505 women (22%). The investigators had no prior knowledge of the parity of the index women or previous clinical findings, and did not participate in their obstetric care. Multivariate logistic regression analysis revealed that sagittal suture overlap was independently associated with CPD. Lambdoid suture overlap could be determined in only 66.5% of examinations primarily because of frequent head deflexion, and intrapartum assessment of the Lambdoid suture was not predictive of CPD. The findings were not affected by parity.
The authors conclude that overlap at the sagittal suture, although not necessarily diagnostic, is useful for prediction of CPD. Lambdoid suture overlap appears to be a normal intrapartum phenomenon and of little predictive value.