A dramatic decline in teen pregnancies and births in Minnesota would have sexual health experts overjoyed if not for the plague of sexually transmitted infections that has occurred simultaneously.

Even as teen pregnancies dropped to a historic low, detected cases of chlamydia and gonorrhea rose again last year, according to a new University of Minnesota analysis. The causes appear to be declining condom use among sexually active teens and wariness about notifying partners of infections.

“That’s just a really hard conversation to have,” said Jill Farris of the U’s Healthy Youth Development-Prevention Research Center. “I don’t think we do a very good job of giving young people the language and confidence” to discuss a sexually transmitted infection with a partner.

The U’s annual adolescent sexual health review gathers data from several state health reports to provide a comprehensive assessment of teens and their sexual health and activities.

One finding: Sexual activity is changing in an era when cellphones and other wireless technology affect parent supervision and teen relationships. Teen pregnancies have dropped 69 percent since 1990, partly because of rising use of birth control pills and long-acting forms of contraception, the researchers said. But it also reflects the fact that teens are having less sex. The report highlighted data from the 2016 Minnesota Student Survey showing that 35 percent of 11th-graders in the state were sexually active — compared to 50 percent nationally.

Farris said sex ed programs are teaching teens good decisionmaking, but she also said technology has made it harder for them to engage in a sexual rendezvous.

“Young people actually have a lot less unsupervised time than they did 20 years ago,” she said. “Young people are almost always in connection in some way to somebody. And somebody almost always knows where they are.”

Similarly, she said, cellphones allow teens to engage in romantic relationships even when they’re not together.

“That connection and that closeness with a potential romantic partner is there, but they’re on their phone and not together, which is hard [to comprehend] for anyone who didn’t grow up with a phone in our hand,” Farris said.

Sexually transmitted infections (STIs) can go up even as teen pregnancies go down, in part because of a transition away from condom use for contraception, the report showed. After remaining fairly constant in recent years, the rate of chlamydia infections among teens jumped 15 percent in 2016.

The optimistic assessment of that number is that mature teens are getting screened more frequently today, allowing previously undetected infections to be discovered. Chlamydia, for example, can present no symptoms for years but result in infertility and other problems over time. But Farris said she suspects there is an actual increase in infections as well.

Recent state legislation permitting expedited partner therapy — giving an infected person an antibiotic prescription to give to a sexual partner — doesn’t appear to have slowed the spread of STIs.

Farris said Minnesota needs more education on the threat of STIs, along with campaigns and opportunities for male sexual partners to get tested.

“If they aren’t having sex, one of the reasons is they are scared of pregnancy,” Farris said. “But I don’t think the same fear is there around STIs. Not that we’re in the business of spreading fear, but we should be … saying you should be just as concerned about one as you are the other.”