More fun with gender

According to my supervisor, this chart (mouse over for link) has been accurate for all the people she's known who have been pregnant, with only one exception. It's based on mother's age at the time of birth and the month in which the baby was conceived.
My own evaluation of it has it right for me, my brother, and Pete & Allie's baby Sophia, but not right for Steve...hmmm.
In any case, its prediction (I'll be 31, and we conceived in November) is that Acorn is a girl!