'16 & Pregnant' Star Autumn Crittendon Cause of Death Revealed

Autumn Crittendon of "16 & Pregnant" fame died from a combination of drugs that sadly took her life ... TMZ has learned.

According to the Virginia Department of Health, the late reality star's official cause of death was toxicity from fentanyl and para-fluorofentanyl ... an illicit synthetic opioid similar to fentanyl.

The agency lists Autumn's manner of death as accidental.

As we reported ... Autumn died back in July, when she was found unresponsive in her bedroom in the Virginia home she was sharing with her kid, her mother and her stepfather.

Paramedics were called and attempted to resuscitate Autumn with CPR ... but those life-saving efforts were unsuccessful.

Autumn was best known for appearing on season 5 of MTV's "16 & Pregnant," which documented her giving birth to her eldest son, Drake, who she welcomed with then-boyfriend Dustin Franklin. She had three children in total.

She was only 27.

Unfortunately, Autumn joins a long list of celebrities who have died from fentanyl, a deadly drug that's caused a ton of overdoses in the U.S.