Progressive Christian writer Rachel Held Evans has been placed in a medically induced coma following health complications.

The 37-year-old blogger and bestselling author of A Year of Biblical Womanhood was placed into a coma on Friday after doctors found that her brain was experiencing seizures, her husband Daniel Evans wrote in an update to her blog. 

"During treatment for an infection Rachel began exhibiting unexpected symptoms," he wrote.

"Doctors found that her brain was experiencing constant seizures. She is currently in the ICU. She is in a medically induced coma while the doctors work to determine the cause and solution."

In another update on Monday, Daniel said she remained in a coma. 

"Rachel is still in a medically induced coma. Drs are working to balance her treatment in an attempt to avoid negative effects of the constant seizures but also avoid possible negative effects of any medications used to sedate her and control them," he said. 

A GoFundMe campaign to help with the medical costs has been started by her friend and feminist Christian writer Sarah Bessey.  She said on Twitter that the outpouring of support had been "overwhelming". 

On Friday, Bessey had asked Christians to join in an hour of prayer for Held Evans. 

"Together let's lift up prayers of thanksgiving and intercession, strength and healing," she said. 

News of Held Evans' condition follows an update she made to her Twitter on April 14 in which she asked followers to pray for her while she was in the hospital battling flu, a urinary tract infection, and a "severe allergic reaction" to the antibiotics she was being treated with.

Church leaders from across the spectrum have been tweeting their support. 

Russell Moore, president of the Southern Baptist Convention's Ethics and Religious Liberty Commission, tweeted: "@rachelheldevans and I are, as you know, theological opposites, and we've debated each other on all kinds of stuff over the years. She needs our prayers right now. 

"Conservatives, progressives, centrists, everybody: let's pray for RHE."

Beth Moore, founder of Living Proof Ministries, said she would be praying for Held Evans "for as long as it takes". 

Kay Warren, the co-founder of Saddleback Church and wife of pastor Rick Warren, asked her 52,000 Twitter followers to "pray with a passion" for Evans.

"Jesus, we run to you, our Help and our Healer, on behalf of Rachel," she tweeted. "In your mercy, please return our sister to us."