President Barack Obama speaks at the 2013 Planned Parenthood National Conference in Washington, Friday, April 26, 2013. President Barack Obama pauses while speaking at the 2013 Planned Parenthood National Conference in Washington, Friday, April 26, 2013. President Barack Obama is introduced by Cecilia Boone, chair of the board of Planned Parenthood, before speaking at the 2013 Planned Parenthood National Conference in Washington, Friday, April 26, 2013. WASHINGTON (AP) - President Barack Obama vowed Friday to join Planned Parenthood in fighting against what he said are efforts by states to turn women's health back to the 1950s, before the Supreme Court legalized abortion nationwide, and singled out the GOP-governed states of North Dakota and Mississippi for criticism. "When politicians try to turn Planned Parenthood into a punching bag, they're not just talking about you," Obama said, becoming the first sitting president to address the abortion-rights group in person. They're talking about the millions of women who you serve. Obama asserted that "an assault on women's rights" is underway across the country, with bills introduced in more than 40 states to limit or ban abortion or restrict access to birth control or other services. "The fact is, after decades of progress, there's still those who want to turn back the clock to policies more suited to the 1950s than the 21st century," he said. And they've been involved in an orchestrated and historic effort to roll back basic rights when it comes to women's health. Last month, North Dakota Republican Gov. Jack Dalrymple signed a law that bans abortions as early as six weeks, or when a fetal heartbeat is detected, making the state the most restrictive in the nation in which to get the procedure. Obama said "a woman may not even know that she's pregnant at six weeks." More than a year ago in Mississippi, a "personhood" ballot initiative that would have defined life as beginning at fertilization was defeated by 58 percent of voters in November 2011, the same election in which staunch abortion opponent Phil Bryant, a Republican, was elected governor. Bryant had campaigned for the initiative. Abortion opponents are expected to soon begin a signature-drive to get a similar initiative on the ballot in 2014 or 2015. "Mississippi's a conservative state, but they wanted to make clear there's nothing conservative about the government injecting itself into decisions best made between a woman and her doctor," Obama said of the voters there. The president lauded Planned Parenthood's nearly 100 years of providing cancer screenings, contraception and other health services for women and assured those fighting to protect abortion rights that they have an ally in him. "You've also got a president who's going to be right there with you, fighting every step of the way," Obama said. In North Dakota, Republican state Rep. Bette Grande, an abortion opponent from Fargo who introduced the bill banning most abortions based on a fetal heartbeat, said she was happy Obama took notice of her state's stance on the issue. He is pointing it out because it's true. We have taken a serious look at the life of a child, and the nation is paying attention to that," she said. We are dealing with life in North Dakota and something as basic as a beating heart. Laurie Bertram Roberts, Mississippi president of the National Organization for Women, said voters in her state, while conservative, did not misunderstand what "personhood" would have meant for women and families. "We understand that when you give a fertilized egg the rights of a person, that affects every aspect of pregnancy and reproductive health," she said. Obama's pledge to stand with Planned Parenthood echoed his rhetoric in last year's presidential campaign after Republican rival Mitt Romney said he'd eliminate the organization's federal funding if elected. That incident, coupled with other issues, led Democrats to begin accusing Republicans of waging a "war on women." Obama went on to win a second term with 55 percent of the female vote, polls showed. The president originally was scheduled to address Planned Parenthood on Thursday night, but the appearance was delayed to allow him to spend more time in Texas with the loved ones of those who were killed or injured in last week's explosion at a fertilizer plant in West, Texas. In his short speech on Friday, Obama made no reference to a pair of abortion-related issues that made headlines in recent weeks. On April 5, a federal judge in New York gave Obama's administration 30 days to begin allowing over-the-counter sales of the morning-after pill, saying the government's decision to limit such sales to those aged 17 and older was "arbitrary, capricious and unreasonable." Planned Parenthood sided with the judge; the administration has yet to say whether it will file an appeal. In Pennsylvania, abortion provider Kermit Gosnell is standing trial on charges of killing babies after they were born alive at his West Philadelphia clinic. He also is charged in the 2009 overdose death of a 41-year-old patient. Closing arguments in the case were set for Monday. Associated Press writers Emily Wagster Pettus in Jackson, Miss., and James MacPherson in Bismarck, N.D., contributed to this report.