According to the federal report, Dr. Shelchkov was called in to give an epidural to a 31-year-old woman at 3 a.m. on May 22, 2020. “Give me air,” she said, before becoming unresponsive. She was intubated and her baby was delivered via C-section. The mother recovered.

A state medical committee later concluded that the episode appeared to be another case of Dr. Shelchkov’s placing the epidural catheter too deep, an error that might happen in one in 1,000 epidural attempts, according to an anesthesiologist the state hired as an expert. Anesthesiologists are usually quick to recognize such mistakes and correct them — before administering a full dose of anesthesia. But Dr. Shelchkov didn’t catch his errors in time.

In June 2020, a pregnant woman complained that Dr. Shelchkov took an hour to place the catheter for an epidural and that she was bleeding heavily from the attempts and unable to walk straight. In response, hospital administrators decided that going forward Dr. Shelchkov should ask colleagues for help after three unsuccessful attempts, according to the federal report.

Dr. Shelchkov, in an interview, claimed the epidural catheter took seven minutes to place, not an hour. In interviews, anesthesiologists noted that placing a catheter sometimes takes a few tries, and that some patients experienced sudden drops in blood pressure or other adverse reactions, regardless of an anesthesiologist’s skill or care.

On July 2, 2020, Ms. Semple arrived at Woodhull a few days past her due date to give birth to her first baby, according to the report. Her partner had recently bought an engagement ring and planned to propose a few days after the birth. They had chosen a name for the baby: Khloe.

The following night, Dr. Shelchkov placed an epidural catheter. Two minutes later Ms. Semple had no pulse.

For a moment, Dr. Shelchkov stood seemingly frozen, according to statements later given by a doctor and nurse to federal inspectors. Then he tried to put Ms. Semple on a ventilator. But, according to the state medical review board, instead of placing the breathing tube down her trachea, he sent it down her esophagus — a mistake he later blamed on the fogged-up goggles worn as a Covid-19 precaution. The ventilator pumped oxygen into her stomach, not her lungs.