For the first time in seven years, the US birth rate increased — by 1 percent in 2014, compared to the year before, the Centers for Disease Control and Prevention report. The increase wasn't universal, though — the teen birth rate dropped by 9 percent, a record low.

There are probably many reasons for this change, but an increase in contraceptive use most certainly played a role. More women are using condoms and the Pill than they were 20 years ago, and IUDs are gaining in popularity because of their ease of use. In fact, if you ask the CDC about it, the answer is pretty clear: the best contraceptives for teens are IUDs and implants — and it looks like their use is paying off.

The most recent peak in teen births occurred in 1991. Back then, there were close to 62 births for every 1,000 women aged 15 to 19. Today, the rate is 24 births per 1,000 women, which means that teen births have decreased by more than 60 percent in a quarter century. It's a slow change, but it's still very good news; children born to teenage parents are more likely to be born prematurely, and they're more likely to suffer from poor health early in life.

That wasn't the only large drop in 2014, however. The US also saw a 2 percent drop among women in their 20s. Much like the teen birth rate, that change is part of an ongoing trend; the birth rate among women in their early 20s has declined steadily since 2007.