By Tony Hanson

PHILADELPHIA (CBS) — The mother of alleged murder victim “Baby Boy A” faced cross-examination in the trial of abortion Doctor Kermit Gosnell, who is charged with murdering seven babes born alive.

The 21-year-old woman, who was 17 at the time of the abortion, told the jury she believed she was 17 to 19 weeks pregnant, but after an ultrasound, Doctor Kermit Gosnell told her the pregnancy was further along, 24 weeks, and that point has been emphasized by the defense. It’s a crucial issue, because abortion is legal in Pennsylvania to 24 weeks.

The prosecution alleges the evidence shows the pregnancy was well beyond Gosnell’s claim.

An employee testified earlier that an ultrasound showed the baby was 29 weeks, and an expert told the grand jury that investigated this case, based on a picture of the baby taken by an employee upset by the size of the dead baby, the gestational age was at least 32 weeks.

Gosnell has pleaded not guilty.