Shoulder dystocia among parous parturients: Birth weight differences of the largest prior vaginal delivery and index pregnancy

To compare the birth weight (BW) of largest prior vaginal delivery versus the index pregnancy with shoulder dystocia (SD). From three centers, births with SD were identified and compared to the largest birth weight of prior delivery at term. Among 304 patients, the mean difference in the BW of those with SD in the index pregnancy and largest prior vaginal delivery was 394 ± 510g (p<.0001). The mean differences in BW of those with dystocia and subsequent brachial plexus injury (BPI; 614 ± 569g) versus those without BPI (384.1 ± 508.3g) were also significantly different (p=0.016). There are significant birth weight differences between current and prior birth weight as a predictor of shoulder dystocia with/without BPI. Unfortunately, these findings cannot be used clinically because of the inaccuracy of estimating birth weight.