You said your girlfriend's pregnant now, how far along is she
This verse progresses chronologically with the order Stan sent his letters. This was one of the first things he brought up in his first letter, so he responds to that. This line implies that Eminem really does care about Stan and feels bad.
It’s also worth noting that the time between letters isn’t really that large — less than nine months — since the baby still was not born at the time of Stan’s suicide, further emphasizing his irrationality.
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