PHILADELPHIA (AP) — A lawyer for a Philadelphia abortion provider charged with killing seven babies allegedly born alive tried Wednesday to show that at least the first baby had died in the womb and that the mother was not as far along in the pregnancy as the prosecution claims.

A young woman who was 17 when she aborted "Baby A" spent several hours testifying in Dr. Kermit Gosnell's murder trial.

The prosecution says she was nearly 30 weeks in her pregnancy. And one of Gosnell's medical assistants, who had testified that late-term babies were routinely cut with scissors after delivery, said she was disturbed by the baby's size and pinkish color.

But defense lawyer Jack McMahon suggested that no babies survive after the drug digoxen is administered into the womb. The drug was used on the teen mother, according to her medical records, which also show her aunt paid $2,750 in cash for the abortion.

McMahon tried to show that the teenager also could have been earlier in her pregnancy.

Prosecutors believe she was well beyond the 24-week limit in Pennsylvania. Gosnell started a three-day outpatient procedure on the teen in 2008 in Delaware, where the limit is 20 weeks. The baby was delivered at his clinic in West Philadelphia.

The medical assistant, Andrienne Moton, has said she was so concerned by the baby's appearance that she took a cellphone picture of it. Moton said this week that late-term babies were routinely cut with scissors after delivery, and she acknowledged that she performed the technique at least 10 times.

McMahon asked the prosecution's medical expert if gestational age isn't an imprecise estimate, with a second-trimester range of about two weeks on either side.

"This isn't an exact science where two plus two equals four?" he asked Dr. Daniel Conway, a Philadelphia neonatologist with St. Christopher's Hospital.

Conway agreed that gestational age is an estimate, but said the estimate is based on a scientific calculation of a long list of variables that includes head size, femur length, skin development and the mother's last menstrual period.

Ultrasound records from Gosnell's clinic show three different measurements for the teen's fetus, two that suggested an age of 29 or 30 weeks, and a much smaller measurement that corresponds with a 24- or 25-week-old fetus. Prosecutors believe Gosnell took new measurements and overruled his staff when women wanted late-term abortions.

But McMahon suggested the doctor had more training than his staff — who allegedly lacked training and licenses for the work they did — and appropriately recalibrated their work.

Gosnell, 72, is charged with first-degree murder in the seven infant deaths, and third-degree murder in a patient's overdose death. He faces the death penalty if convicted in the infant deaths.

The jury of seven men and five women, along with five alternates, endured graphic testimony and photographs throughout the day, including one that showed an approximately 2-inch gash in the back of a baby's neck, where Moton said the babies were routinely "snipped" to "ensure fetal demise."

Conway testified that even premature babies, born in the second trimester, feel pain. He said doctors define them as "born alive" if there is a heartbeat. At that point, he said, they are treated as patients and, at a minimum, kept comfortable, even if they are deemed too young to survive.

As for viability, Conway said that babies with a gestational age of 27 to 30 weeks have an 85 percent chance of survival, and a low risk of serious disabilities. At 22 to 24 weeks gestation, the chances are not good, he said.

Conway was also asked about the collection of fetal feet found in jars at Gosnell's clinic. Moton told jurors that Gosnell kept them in cases where the family wanted DNA, perhaps for legal purposes. Investigators, though, have said they can't find any medical explanation for the macabre practice.

"There are alternate ways of preserving DNA," Conway said, "and the foot itself is a weak prediction of gestational age."