He was expected to make a statement Thursday; the aide was not authorized to discuss the matter before Franks' announcement.
Arizona Republican Trent Franks says he is resigning from the House because he discussed with two female staff aides whether they would consider being a surrogate mother.
"I have recently learned that the Ethics Committee is reviewing an inquiry regarding my discussion of surrogacy with two previous female subordinates, making each feel uncomfortable", the Republican said. A spokesman for Franks did not respond to a request for comment on that claim.
Franks, a staunch conservative, said in his statement Thursday that he never physically intimidated, coerced or attempted to have sexual contact with any member of his congressional staff.
Franks says he had become familiar with the surrogacy process in recent years, and "became insensitive as to how the discussion of such an intensely personal topic might affect others".
Franks explained in his statement that he and his wife have long struggled with infertility. They had twins through a surrogate, but subsequent attempts to have another child by either adoption or another surrogate fell through. He previously covered D.C. politics and government from 2007 to 2015. Al Franken, D-Minn., resigned his seat after multiple allegations of sexual misconduct and as the House Ethics Committee opened a separate probe into Rep. Blake Farenthold, R-Texas. He said he'd depart in a few weeks.
Mr. Franks, who made his name with strident social conservatism and adamant opposition to abortion in all forms, would be the third lawmaker to step down from office this week. Franks won an eighth term last fall by 37 points.