The last of the ten plagues was Makat Bechorot, where all firstborn Egyptians were killed overnight.

We know from Pidyon Haben that a firstborn son, born after a mother had miscarried (after more than 40 days) is not required to have a Pidyon performed.

So I am wondering, does this change of status to firstborns born after miscarriages apply to other situations as well?

Were post-miscarriage "firstborn" Egyptians subject to the plague or was it just pure firstborns?

  • Actually, Pidyon HaBen applies to a mother's firstborn. The Midrash says that Makat Bechorot applied to every father's firstborn; this led to a lot of surprises that night, as not everyone's fatherhood was as stated! – Shalom Apr 21 '16 at 18:17