No, nothing to do with an impending birth. Banns are what was done, and still are. Banns are posted for 3 weeks in case anyone has any serious objections for the party's to get married.
It was fairly common for the wives to be pregnant at the time of marriage. I have plenty of those in my tree, including my paternal Grandmother.

A marriage by Licence was a quicker way to get married, but you had to pay quite dearly for that. If there were any serious objections afterwards, they could lose a serious amount of money for the Licence fee, as they would have have potentialy lied if an objection was upheld.
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