A newly fired Catholic high school math teacher in Austin, Minn., carried out a monthslong sexual relationship with one of her 17-year-old students and the two discussed in recent weeks that she may be carrying their child, according to felony charges.

Mary F. Gilles, 28, who lives just northeast of Austin and taught at Pacelli High School, was charged with six counts of third-degree criminal sexual conduct, a charge based on the boy's age and the defendant being more than four years older.

Gilles, who was arrested at her home Monday, remains in Mower County jail in lieu of $60,000 bail.

School officials said she was fired Tuesday.

According to the charges, sexual activity between the two occurred in Gilles' rural home beginning in February. It halted during the summer and then resumed in September.

In an interview this week with police detectives, Gilles admitted to the sexual nature of the relationship and also acknowledged that she knew the boy was 17, the criminal complaint read.

Police reviewed e-mails between the two, with the last few referring "to the defendant possibly being pregnant," the complaint added.

According to the charges:

School administrator Laura Marreel told police that a staff member reported seeing Gilles and the boy together on Friday in the auditorium "at a late hour."

Acting on what she described as a "gut feeling," Marreel accessed the teen's school e-mail account but found nothing suspicious. However, she found the password to his personal e-mail account and uncovered numerous e-mails with "sexual relationship content."

The administrator also "observed that the last few [correspondences] referred to the defendant possibly being pregnant," the complaint read.

Under questioning by a police detective, the boy said he "has a close relationship" with his math teacher that began in February.

He said he used a condom during the four or five times he had intercourse with Gilles from February until June.

After his return in late August from summer break, the two had sex twice in September, the teen continued.

The teacher told detectives that she and the boy had sex once a month.

Gilles is a native of southeastern Minnesota, and attended Mount Mercy College in Cedar Rapids, Iowa, and the University of Northern Iowa in Cedar Falls.

An unrelated shake-up

In additional difficulties this week for Pacelli Catholic Schools that administrators say is unrelated to Gilles' case, the board of trustees has placed school President Jim Hamburge and Principal Mary Holtorf on leave "pending the results of an internal investigation related to their administrative functions."

The board anticipates that the investigation will take several days to complete, its statement continued without further elaboration.

Paul Walsh • 612-673-4482