The court would wait for the baby. It would not spare the mother.
Under English common law, a woman convicted of a capital crime who was found to be ‘quick with child’ — pregnant, past the point of detectable movement — received an automatic stay of execution until after she gave birth. The principle predates the witch trials by centuries and had nothing to do with mercy for the mother specifically: it existed to avoid punishing an unborn child for a crime it hadn't committed.
Elizabeth Proctor was one of the most prominent people caught in the outbreak. Her husband, John Proctor, was convicted alongside her and hanged on August 19, 1692 — one of the few men executed in the trials, and one whose blunt public skepticism of the girls' fits (see: Record 04) very likely accelerated his own conviction.
Elizabeth's sentence was stayed on account of her pregnancy. What saved her, in the end, wasn't leniency — it was timing. Spectral evidence was barred from the courts that October, the special court was dissolved, and by the time her case would have come back around for execution, the entire apparatus of the trials had collapsed. She gave birth, and eventually walked free.
It's worth being precise about what the exception actually was: a postponement with a clock attached, not a pardon. Had the trials continued running on their original schedule a few months longer, the stay would very likely have run out before it saved her.
A delay is not mercy. It's scheduling.