Study on the cephalopelvic relationship with cephalic presentation in nulliparous full-term Chinese pregnant women by MRI with three-dimensional reconstruction.

<bold>Purpose: </bold>To analyze the relationship between fetal head size and maternal pelvis size using magnetic resonance imaging (MRI) with a 3-D reconstruction technique.<bold>Methods: </bold>A total of 301 nulliparous full-term Chinese pregnant women with cephalic presentation were enrolled and received MRI examinations before labor onset. Data were collected and imported into Mimics software to reconstruct the maternal pelvis and fetus.<bold>Results: </bold>Of 301 pregnant women, 212 underwent vaginal delivery and 32 received cesarean section. The body mass index (BMI) was significantly different between the vaginal delivery group and the suspected cephalopelvic disproportion (CPD) group; the larger the BMI, the higher was the risk of CPD. The transverse diameter of the pelvic inlet and the posterior sagittal diameter of the midpelvis were significantly larger in the vaginal delivery group, compared with the suspected CPD group. Fetal weight > 3.5 kg could be used as a diagnostic indicator for CPD.<bold>Conclusions: </bold>BMI is a risk factor for CPD, and fetal weight < 3.5 kg is an important diagnostic indicator for natural delivery in Chinese pregnant women. [ABSTRACT FROM AUTHOR]