What is the greatest risk factor for shoulder dystocia during delivery?

The greatest risk factor for shoulder dystocia during delivery is maternal type 2 diabetes mellitus. This condition is associated with larger-than-average babies, a phenomenon known as macrosomia, which significantly increases the likelihood of the baby's shoulder becoming lodged behind the mother's pelvic bone during delivery. The excess insulin produced in response to high blood sugar levels can lead to fetal growth abnormalities, making the fetus larger and more prone to complications during delivery.

Conversely, while factors such as maternal chronic hypertension, male fetal sex, and fetal gestational age may influence delivery outcomes, they are not as strongly correlated with the occurrence of shoulder dystocia as maternal diabetes. Maternal chronic hypertension does raise the risk of various complications during pregnancy but does not have the same direct impact on fetal size and shoulder dystocia as diabetes. Male fetal sex and fetal gestational age may contribute to delivery challenges but are not considered primary risk factors for shoulder dystocia in the same way that maternal type 2 diabetes is.