(CNN) With a swipe of a pen Monday, Mississippi Gov. Phil Bryant signed into law a bill that prevents women from getting abortions after 15 weeks of pregnancy. His state, effective immediately, now holds the distinction of having the earliest abortion ban in the nation.

"I was proud to sign House Bill 1510 this afternoon. I am committed to making Mississippi the safest place in America for an unborn child, and this bill will help us achieve that goal," Bryant tweeted Monday

Lt. Gov. Tate Reeves echoed that sentiment Monday, tweeting "It's a great day in Mississippi" along with a picture of the signing.

Also known as the Gestational Age Act , Mississippi's new law makes exceptions only for medical emergencies or cases in which there's a "severe fetal abnormality." There are no exceptions for incidents of rape or incest.

The law also puts physicians on notice. Doctors who perform abortions after 15 weeks will be required to submit reports detailing the circumstances. If they knowingly violate the law, their medical licenses will be suspended or revoked in Mississippi. If they falsify records, they will face civil penalties or be forced to pay fines of up to $500.

The measure is just one in a string of efforts to diminish access to abortions in Mississippi, critics say.

"Abortion is a safe medical procedure and it is a critical part of the broad spectrum of reproductive health care that a woman may use in her lifetime," said Felicia Brown-Williams, Mississippi state director for Planned Parenthood Southeast Advocates , in a statement. "This ban is not only unconstitutional -- it endangers women's health care across our state. If legislators truly cared about women's health, they would be focused on ways to improve access to health care for women, not restrict it."

Access to abortions in Mississippi was already highly restrictive.

It is among a small handful of states that has one remaining clinic: in this case, Jackson Women's Health Organization. Although Mississippi is among the states with a 20-week ban, up until the enactment of this latest bill, the cutoff time for abortions at the Jackson clinic was 16 weeks. And since hospitals won't perform abortions, the resulting one-week change brought on by this new law is "arbitrary," based on "capricious whim" and a way to "feed political meat" to a political base, said Dr. Willie Parker, board chairman of Physicians for Reproductive Health

Mississippi is the only state in the country that requires physicians who perform abortions to be board-certified or board-eligible obstetrician-gynecologists, a fact that's being challenged in court as unconstitutional by the Center for Reproductive Rights. Parker, an OB/GYN, explained that he could be trained in a plastic surgical procedure and be free to perform that procedure in Mississippi, even though he's not a board-certified plastic surgeon. But a family physician, a surgeon or an internist trained to perform abortions isn't given the same leeway.

Mississippi also requires in-person counseling and a 24-hour waiting period before receiving an abortion, which means women must make repeat trips to the facility -- a fact that's especially burdensome for those living outside Jackson. Health plans under the Affordable Care Act, insurance policies for public employees and public funding for abortions can be applied only in cases of rape, incest, fetal impairment or when a life is endangered, according to the Guttmacher Institute

About 2,000 women a year in Mississippi receive abortions, Parker said. The vast majority, 88%, receive them in the first 12 weeks of pregnancy. So by 15 weeks, he estimates, 200 women in Mississippi who should have access to an abortion no longer will.

For women living in poverty who need time to gather resources to pay for an abortion and for those outside Jackson who need to find ways to cover additional expenses associated with travel, House Bill 1510 will close the door to a procedure that's been a legal right for women since the passage of Roe v. Wade in 1973.

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Proponents of the bill, like Mississippi State Rep. Dan Eubanks, argue that this law will do what's best for women.

"Beyond the obvious debate of trying to save the lives of innocent babies, there is the often less discussed issues that relates to the health of the mother who receives an abortion," Eubanks wrote in an email. "When did looking out for the life, health and overall wellbeing of a child or its mother start getting labeled as extreme in this country?"

Eubanks says that the longer a woman carries a child in her womb, "the greater the potential she will suffer from psychological, emotional, and physical damages as an outcome," though that contention is generally disputed by those who advocate for safe access to abortions.

The new Mississippi law is expected to be challenged in court.

The Center for Reproductive Rights points out that similar efforts in other states -- Arizona, North Dakota and Arkansas -- were shot down on constitutional grounds. And the advocacy group expects that this bill to ban "pre-viability abortion" will similarly be stopped.

"Mississippi politicians' flagrant assault on reproductive rights will not go unchallenged," said Lourdes Rivera, senior vice president of US programs at the Center for Reproductive Rights, in a written statement. "This bill is dangerous and unconstitutional. The Center is prepared to answer any attempt to undermine 40 years of Supreme Court precedent with the full force of the law."