After months of criticism over the troubled rollout of the Affordable Care Act, U.S. Health and Human Services Secretary Kathleen Sebelius has announced her resignation.

U.S. President Barack Obama officially made public Sebelius' departure April 11, praising her as "a tireless advocate for women's health."

However, Rep. Diane Black (R- Tenn.), a co-sponsor of pro-life legislation proposed to clarify ambiguities about abortion funding in the Affordable Care Act, criticized Sebelius' tenure.

Black noted in an April 11 statement that the controversial federal contraception mandate was issued under Sebelius' leadership.

She charged that the mandate "forces those who stand up for their conscience to choose between paying crippling fines that could shut down their business or dropping healthcare coverage for all their employees."

As Secretary of Health and Human Services since 2009, Sebelius was responsible for the implementation of the Affordable Care Act after its passage in 2010. In recent months, she had drawn criticism for the problems experienced in the state health care exchanges and technical glitches troubling the rollout of the HealthCare.gov website.

Sebelius has also been the face of the federal contraception mandate, a directive issued under the authority of the Affordable Care Act. The mandate requires employers to offer health insurance plans including coverage of contraception, sterilization and some drugs that can cause early abortions.

Despite a series of revisions to the mandate, critics argue that it fails to respect the religious freedom of employers who have moral and religious objections to its demands. More than 300 plaintiffs have sued Sebelius and her department over the mandate, and the U.S. Supreme Court will rule on two cases involving the mandate this summer.

In announcing her resignation, Obama acknowledged that "there were problems" with the implementation of the Affordable Care Act and Healthcare.gov, but praised the secretary's work to enroll people in the exchanges.

Obama also announced his nomination of Sylvia Mathews Burwell, director of the White House Office of Management and Budget, to replace Sebelius in the position.

In her resignation speech, Sebelius called her time as HHS Secretary the "most meaningful work I've ever been a part of" and "the cause of my life."

Cecile Richards, president of Planned Parenthood Federation of America, praised the outgoing secretary in an April 10 tweet, writing "Kathleen Sebelius did more for women's health than anyone in history - our champion!"

She added in an April 11 tweet that "27 million women are benefiting from no-cost preventive health care, including birth control."

Sebelius had also sparked controversy in her previous role as governor of Kansas due to her Catholic faith and adamant support for abortion.