This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Medical & Surgical Illness Complication Pregnancy, Subject name: Gynaecology & Obstetrics
All are risk factors for shoulder dystocia except: 
Select and explain. 
A. Maternal diabetes, B. Trisomy 18, C. Maternal obesity, D. Post term pregnancy
B: Trisomy 18
Answer: B: Trisomy 18 
Explanation: Ans. B. Trisomy 18a. Increased risk of shoulder dystocia is seen in the following conditions:b. Fetal macrosomiac. Prior history of shoulder dystociad. Maternal obesitye. Maternal DM/Gestational diabetesf. Post term pregnancyg. Prolonged 2nd stage of laborh. Instrumental deliveryi. Anencephalic fetusj. Trisomy 18 is associated with IUGR, therefore no increased risk for shoulder dystocia.