Shayne Lamas in a Coma -- Loses Baby

UPDATE: 2:23 PM PT ... Shayne's husband, Nik Richie, just went on the record with TMZ, telling us, "Shayne had a life-saving emergency surgery. She is on a ventilator system and is in a sedation-induced coma. Her vital signs are now currently stable."

Tragedy has struck the Lamas family -- Lorenzo Lamas' daughter Shayne (famous for her stint on "The Bachelor") has just lost her baby from a freak pregnancy complication ... and she's in a coma.

TMZ broke the story last month -- Shayne and her husband Nik Richie (founder of TheDirty.com) were pregnant with their second child. Shayne was 16 weeks along.

But Sunday, at 7:35pm, law enforcement sources tell us paramedics were called and rushed to Nik and Shayne's OC home after Shayne collapsed. She was taken to the hospital.

When Shayne arrived, doctors determined she was bleeding internally around her uterus and the situation was dire. Doctors were stumped and brought in specialists to figure out what was causing the bleeding.

Shayne lost the unborn child during surgery.

We're told Shayne is currently in a coma and not breathing on her own. Doctors are optimistic about her recovery.

Nik and Shayne's dad Lorenzo are by her side.