Department of Obstetrics and Gynecology, University Hospital of Parma, Parma, Italy.
Department of Medicine and Surgery, Unit of Surgical Sciences, University of Parma, Parma, Italy.
Acta Obstet Gynecol Scand. 2021 Oct;100(10):1917-1923. doi: 10.1111/aogs.14226. Epub 2021 Jul 26.
The obstetric conjugate represents the shortest anteroposterior diameter of the birth canal and it reflects the capacity of the pelvic inlet to allow the passage and the engagement of the fetal head. The antepartum evaluation of this parameter may be attempted at digital examination to predict the risk of cephalopelvic disproportion, but the accuracy of clinical pelvimetry is notoriously poor. The aim of our study was to describe the sonographic measurement of the obstetric conjugate at transabdominal 2D-ultrasound and to assess its reproducibility.
This is a prospective cohort study conducted at a tertiary University hospital. A non-consecutive series of pregnant women with uncomplicated singleton pregnancies attending the antenatal clinic for routine booking from 34 weeks of gestation onward were included. The ultrasound probe was longitudinally placed above the level of the symphysis and the interpubic fibrocartilaginous disk was visualized. Then the promontory was identified as the most prominent segment of the sacral vertebral column. The obstetric conjugate was measured as the distance between the inner edge of the interpubic disk and the promontory. The inter- and intraobserver repeatability of this measurement was calculated using the intraclass correlation coefficient (ICC) and the Bland-Altman method.
In all, 119 women were considered eligible for the study; of these, 111/119 (93.3%) women were included in the analysis with a median gestational age of 36.0 (35.0-37.0) weeks. The mean obstetric conjugate measurement was 11.4 ± 0.93 mm for the first operator and 11.4 ± 0.91 mm for the second operator. The overall interobserver ICC was 0.95 (95% [confidence interval] CI 0.92-0.96) and the overall intraobserver ICC was 0.97 (95% CI 0.96-0.98). Limits of agreement ranged from -0.84 to 0.80 for interobserver measures and from -0.64 to 0.62 for intraobserver measures. The degree of reliability was also analyzed for women with a body mass index ≥30 and for women with a gestational age ≥37 weeks. The inter- and intraobserver ICCs were respectively 0.97 (95% CI 0.90-0.98) and 0.98 (0.95-0.99) in the former group and 0.96 (95% CI 0.93-0.98) and 0.97 (95% CI 0.95-0.98) in the latter group.
Our study demonstrated that among pregnant women at term gestation, sonographic measurement of the obstetric conjugate is feasible and reproducible.
产科结合代表了产道的最短前后径，反映了骨盆入口允许胎儿头部通过和衔接的能力。通过数字检查来评估这个参数可以预测头盆不称的风险，但临床骨盆测量的准确性是出了名的差。我们的研究目的是描述经腹部 2D 超声测量产科结合的方法，并评估其可重复性。
这是一项在三级大学医院进行的前瞻性队列研究。连续纳入了从 34 周妊娠开始在产前门诊进行常规检查的、无并发症的单胎妊娠孕妇。将超声探头纵向放置在耻骨联合上方，可显示耻骨联合间纤维软骨盘。然后，耻骨联合上方的骶骨椎体最突出的部位被确定为耻骨联合。产科结合的测量方法是耻骨联合内缘与耻骨联合上方之间的距离。使用组内相关系数（ICC）和 Bland-Altman 方法计算该测量的组内和组间可重复性。
共有 119 名妇女被认为符合研究条件；其中，111/119（93.3%）名妇女被纳入分析，中位孕龄为 36.0（35.0-37.0）周。第一次测量的产科结合平均值为 11.4±0.93mm，第二次测量的平均值为 11.4±0.91mm。总的观察者间 ICC 为 0.95（95%置信区间 0.92-0.96），总的观察者内 ICC 为 0.97（95%置信区间 0.96-0.98）。观察者间测量的一致性界限为-0.84 至 0.80，观察者内测量的一致性界限为-0.64 至 0.62。还分别对 BMI≥30 的妇女和孕龄≥37 周的妇女进行了可靠性分析。前者的观察者间和观察者内 ICC 分别为 0.97（95%置信区间 0.90-0.98）和 0.98（0.95-0.99），后者的观察者间和观察者内 ICC 分别为 0.96（95%置信区间 0.93-0.98）和 0.97（95%置信区间 0.95-0.98）。
我们的研究表明，在足月妊娠的孕妇中，产科结合的超声测量是可行和可重复的。
