The U.S. pregnancy rate has hit a record low, according to the most available data released Friday.

Births and abortions were both down over the same time in 2010 — although other surveys looking at more recent months show births ticking back up.

Abortions also hit a record low, according to the research by the National Center for Health Statistics (NCHS) and the Guttmacher Institute.

Related: Record Low Teen Birth Rate Not Low Enough, CDC Says

“The pregnancy rate for women in the United States continued to decline in 2010, to 98.7 per 1,000 women aged 15–44, a record low for the 1976–2010 period. This level was 15 percent below the 1990 peak,” wrote researchers Sally Curtin and Joyce Abma of the NCHS and Kathryn Kost of the Guttmacher Institute.

“The estimated number of pregnancies dropped to 6.155 million in 2010, the lowest number since 1986,” they added.

The survey uses 2010 data because that’s the latest available for the kind of analysis they did. Other research by the Centers for Disease Control and Prevention finds the birthrate rose by 1 percent in 2014 — the first increase in seven years — thanks largely to older mothers giving birth.

The biggest drops in pregnancy rates were in younger women. Few girls 14 and under have babies but this number dropped by 67 percent in 2010 compared to 1990, they found. And pregnancies among teenagers 15 and older fell by 50 percent.

Other studies have shown more teens are using contraceptives and that fewer teens are having sex, which both add up to record low rates of teen births.

The researchers found the rates of pregnancy among women 40 and older rose by 70 percent.

The researchers just looked at statistics and cannot say why pregnancy rates went down.

But in other studies, Guttmacher researchers have found that half of all pregnancies in the U.S. are unintended, that teenagers do not use the most effective methods of birth control, and stick to condoms instead of implantable birth control drugs.

Federal data show that the U.S.teenage birth rate is still seven times higher than rates in other wealthy countries.

And while the rate of newborn deaths in the U.S. have hit a record low, rates are still triple the rate of Japan or Norway and double the rate of Ireland, Israel or Italy.