"I was on the (birth control pill) when I became pregnant," Percival, 25, said. "Deciding to terminate at eight weeks was just utterly horrible but I couldn't cope with the anguish of losing another baby."
A short time after the abortion, Percival felt a fluttering in her stomach. She went to the doctor for a scan and discovered she was 19 weeks pregnant.
"I couldn't believe it,' Percival said. "This was the baby I thought I'd terminated. At first I was angry that this was happening to us, that the procedure had failed. I wrote to the hospital, I couldn't believe that they had let me down like this.
"They wrote back and apologized and said it was very rare," she added.
Dr. Manny Alvarez, managing health editor for FOXNews.com, said Percival's situation is actually quite common.
"Women that have early terminations in weeks six, seven and eight, many times the pregnancy is so small that doctors miss removing the baby," Alvarez said. "The danger is that the failed attempt can damage the baby. That is why these patients who get early terminations need follow-ups."
Another scan a week later confirmed the baby also had kidney problems, but doctors told the couple the baby was likely to survive, so they decided he deserved another chance at life.
In November, Finley was born three weeks premature. He had minor kidney damage but is expected to lead a normal life.
Just to repeat: "The danger is that the failed attempt [to kill the child] can damage the baby."