A pregnant woman whose son has ornithine transcarbamylase (OTC) deficiency comes for genetic counseling. A detailed ultrasound at 18 weeks shows a normal female fetus. Which of the following is the MOST important information to collect to assess risk in the current pregnancy?
A. results of her partner's carrier testing
B. maternal symptoms of hyperammonemia
C. orotic acid and ammonia levels in her son
D. maternal diet history