Proportions between fetal head and abdominal circumference good predictors of Shoulder Dystocia
Shoulder dystocia (ShD) is the inability to deliver the baby's shoulders naturally. The condition affects approximately 0.15% to 3% of vaginal deliveries. Although most newborns recover from this without permanent harm, up to 20% of cases may result in temporary injuries such as brachial plexus damage, fractures, and hypoxic-ischemic encephalopathy. Maternal complications, including perineal damage, postpartum haemorrhage, and mental stress, can also arise from shoulder dystocia.
A recent study published in the International Journal of Gynecology and Obstetrics has concluded that operative vaginal delivery, vaginal birth after cesarean (VBAC) and sonographic proportions between the abdominal circumference (AC) and fetal head are independently associated with ShD. Researchers in this study highlighted that women with these factors should get attention.
This study included women with neonatal birthweight <3500g. researchers compared cases of ShD to other deliveries and analyzed risk factors for ShD among women delivering <3500g newborns. This was a retrospective case–control study of all term live-singleton deliveries (2011–2019).
Key findings from this study are:
- There were 0.19% ShD cases among neonates <3500 g.
- The factors independently associated with ShD included operative vaginal delivery, VBAC, sonographic abdominal circumference to biparietal diameter ratio (3.73 among ShD vs. 3.62,) and sonographic abdominal circumference to head circumference ratio (1.036 among ShD vs. 1.011).
- The OR were 2.78, 2.74, 1.35 and 3.04 respectively.
They said, "Our study is the largest study addressing ShD among neonates weighing <3500 g. The proportions between the fetal head and abdominal circumference better predict ShD than the newborn fetal weight, and VBAC is associated with ShD."
A previous study conducted over three decades ago, focusing on an American population, reported a ShD rate of 0.5% among neonates weighing less than 3500 g.
The present study had limitations like retrospective design, limited power of sample size, inherent bias, and selection bias.
Reference:
Levin, G., Meyer, R., Cahan, T., Shai, D., & Tzur, A. (2023). Shoulder dystocia in delivery of neonates <3500 grams. International Journal of Gynecology & Obstetrics. https://doi.org/10.1002/ijgo.15204
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