The medical term is often used for natural miscarriages.
The article says it happened in 1992.
Fetal tissue from murdered babies wasn’t legal until 1993:
https://saynsumthn.wordpress.com/2015/07/20/1993-clinton-signs-fetal-tissue-research-law/
That makes me think the baby body parts (not tissue) he studied from was from a natural miscarriage.
Also known as a "spontaneous abortion".