Abortion rates continue fall in the US, decreasing by nearly a quarter in less than a decade, new Centers for Disease Control and Prevention (CDC) data reveal.

In 2016, a total of 623,471 abortions were performed in the US, declining two percent from the previous year.

The report authors dubbed the number, rate and ratio of abortions to live births 'historic lows.'

Most experts argue that the declining abortion rates come too soon to reflect changes affected by abortion restrictions and bans enacted in conservative states.

Instead, the CDC scientists say the shift likely indicated that efforts to reduce unintended pregnancies - by encouraging the use of long-acting contraception, like IUDs - are working and driving the decrease in teen pregnancies reported by the CDC earlier today.

The number of abortions performed in the US fell 24 percent in just 10 years, the CDC reports

After abortion was federally legalized by the historic Roe v Wade Supreme Court decision in 1973, abortion rates rose steadily to reach a peak of nearly 30 per 1,000 women between 1980 and 1981, according to prior Guttmacher Institute research.

Since then, abortions have trended downward, hitting record lows year after year since 2007.

Abortions are most prevalent among women in their 20s, according to the new figures.

This means that this age-group is also largely responsible for the historic drop in abortion rates.

In contrast, teen abortion rates across the US are low. Medical and surgical abortions for 15- to 19-year-olds accounted for just 9.4 percent of all abortions. Only 0.3 percent were for girls under 15.

Between 2007 and 2016, the number abortions for teenagers decreased by 43 percent.

This is encouraging, and falls in line with the reduction in teen pregnancies reported by the CDC earlier on Wednesday.

Most of the abortions performed in 2017 - nearly 60 percent - were performed for women women who had already had one or two children.

Women who had never had abortions accounted for the second greatest proportion of abortions, at just over 40 percent.

Women in their 20s accounted for the highest percentage (blue), rate (red) and ratio (green) of US abortions in 2017. Under-15s had a very low rate of abortions, but a high ratio of abortion to live births, the CDC reported

Medical abortions - which involve taking a pair of drugs to terminate pregnancy, now account for almost 28 percent of all abortions.

About 60 percent are still done surgically.

The researchers also found that the majority of abortions performed early on in pregnancy.

'Unintended pregnancy is the major contributor to induced abortion,' the study authors noted.

'Increasing access to and use of effective contraception can reduce unintended pregnancies and further reduce the number of abortions performed in the United States.'

And previous CDC research suggests that exactly that is happening.

During the period from 2011 to 2015, just eight percent of women were using long-acting reversible contraceptives (LARCs).

But by the period spanning 2015 to 2017, that rate had surged to 11.3 percent, an increase of over 40 percent.