The rate of abortions in the United States is down significantly, but women’s health advocates say those numbers don’t tell the entire story.

They say the reasons for the decrease are important to understand, especially with a new, more conservative administration entering the White House in January.

This week, the Centers for Disease Control and Prevention (CDC) released an annual report that shows both the number and rate of abortions recorded in the United States hit a 45-year low in 2013.

In all, the CDC recorded 664,435 abortions in 2013 from the 47 states that release abortion statistics, as well as the District of Columbia and New York City.

The abortion rate in 2013 was slightly more than 12 abortions per 1,000 women between the ages of 15 and 44. That’s 5 percent fewer than the previous year and a decrease of 20 percent from 2004.

The statistics come with a caveat, however.

The CDC doesn’t receive abortion data for three states — California, Maryland, and New Hampshire — that have a combined population of more than 46 million. In 1990, when California still released abortion statistics, more than 1.4 million abortions were recorded.

The last time the national abortion rate was lower than the 2013 figures was 1971, two years before the landmark Supreme Court Roe v. Wade ruling that gave all U.S. women the right to have access to abortion services.

Read more: Restrictive laws may be driving up self-induced abortions »

Access varies from state to state

Despite the Roe v. Wade decision, it can still be difficult for many women to access clinics that perform abortions.

Abortion rates were radically different from state to state — New York recorded 24 abortions per 1,000 women aged 15 to 44, while Mississippi’s rate was 3.6 per 1,000 women in the same age range.

“We’ve seen what it means for people who are forced to cross state lines, travel hundreds of miles, or wait weeks to get an abortion, if they can at all,” Erica Sackin, director of political communications for Planned Parenthood Federation of America and Planned Parenthood Action Fund, told Healthline.

“These restrictions have a disproportionate impact on those who already face far too many barriers to health care — people of color, people who live in rural areas, or people with low incomes,” Sackin said. “Some may be fearful to seek healthcare at all, if it means risking deportations or being stopped and frisked and arrested for no reason. This cannot be what it means to live in America in 2016.”

Healthline contacted several anti-abortion organizations, but none of them provided comments for this story.

Read more: The battle over abortion heats up »

Possible reasons for decrease

The CDC report points to several possible reasons for the decrease in abortions.

They include increased contraceptive use and better healthcare plans. In addition, teen pregnancy rates in the United States are at a 40-year low.

“We can’t say with certainty what caused abortion rates to go down, but we do know that birth control and sex education are the most important factors in reducing unintended pregnancy and the need for abortion,” said Sackin. “We believe the decrease in abortion has more to do with the expansion of access to birth control and increased use of the most reliable methods of birth control, rather than laws that restrict access to safe and legal abortion.”

Sackin points out that Planned Parenthood health centers have seen a 91 percent increase in the use of intrauterine devices (IUDs) and implants since 2009.

While contraceptive use and access is on the rise nationally, Sackin notes that this sometimes isn’t the case at the state level.

“In addition to the negative impact on women’s lives, state laws restricting abortion don’t make abortion safer,” she said. “States passing laws that restrict access to abortion are also often restricting access to birth control, cutting family planning funding, and in some cases are dealing with external factors that contribute to a rise in the need for abortion.”

Read more: Mike Pence’s record on women’s health issues »

Abortion and the Trump administration

The abortion issue took center stage at the third and final presidential debate in October, with Republican nominee Donald Trump proposing a federal ban on abortions after the 20-week mark.

While only 1.3 percent of abortions recorded by the CDC occurred after the 20th week of pregnancy, Trump’s willingness to reopen the abortion debate could be a sign of things to come now that he’s the president-elect.

“We have grave concerns about President-elect Donald Trump’s announcement that extreme women’s health opponent Representative Tom Price is his nominee to be secretary of Health and Human Services,” said Sackin. “Tom Price poses a grave threat to women’s health in this country. If Price had his way, millions of women could be cut off from Planned Parenthood’s preventative health services like birth control, cancer screenings, and STD tests. Price could take women back decades.”

Despite the prospect of abortion opponents in Trump’s cabinet, Sackin says Planned Parenthood will continue with their mission.

“Planned Parenthood has approximately 650 health centers across the country and a presence in all 50 states. We are committed to getting people the care and information they need, whether it’s in a health center or on their phone — no matter where they are. That’s never changing,” Sackin said.