We read with great interest the article by Harper et al. The authors report that radiographic measures of the mid pelvis have certain predicable functions for cesarean delivery. This prediction is particularly important for women who have had a previous cesarean delivery because they have concerns about morbidity from a failed trial of labor after cesarean delivery. However, only 28 of 426 women (6.6%) were given a definitive answer on the decision of cesarean delivery before a trial of labor, which has no sufficient preponderance compared with the magnetic resonance imaging. On the contrary, whether to choose a trial of labor remained unclear for the rest of the 93.4% of women. They got no substantial benefits. Considering the fact that implementation of x-ray pelvimetry into clinical use will result in exposure of the fetus to more or less ionizing radiation, it would not prove worthwhile to apply this technology.

The authors noted that the risks and benefits of x-ray pelvimetry should be weighed individually. Actually, women would benefit from x-ray pelvimetry only when it was applied to a woman with an anteroposterior diameter of <9.0 cm. That is to say, it would be ideal to identify women who will have a cephalopelvic disproportion before they undergo radiographic pelvimetry. Eventually, obstetricians will have to use other methods to assess cephalopelvic disproportion. Radiographic pelvimetry seems to be less beneficial than other methods, which is a major limiting factor for its clinical implementation.

Successful labor depends on 3 correlative variables: the pelvis, fetus, and uterine contraction. X-ray pelvimetry assesses only the bony pelvis, which does not include soft tissue pelvis that is a necessary part of the birth canal and the other 2 variables. Therefore, clinical utility of x-ray pelvimetry remained controversial. One of the few randomized trials that studied the clinical usefulness of x-ray pelvimetry for the prediction of cephalopelvic disproportion shows that pelvimetry is not necessary before a trial labor and is a poor predictor of the outcome of labor. Overall, it would be better that x-ray pelvimetry be performed as a complementary part of the treatment in patients for whom a trial of labor after cesarean delivery was planned, rather than to be performed for women with low risks.