The impulsiveness and disorganization associated with ADHD appear to make girls with the disorder more likely to become pregnant, said lead researcher Charlotte Skoglund, a clinical neuroscientist with the Karolinska Institute in Stockholm.
"Clearly, standard of care in girls and women with ADHD should include active efforts to prevent teenage pregnancies in order to reduce long-term adverse consequences for both women and their children," Skoglund said.
The findings were published Oct. 2 in JAMA Network Open.
The new study supports prior research that came to similar conclusions, said Dr. Eugene Arnold, professor emeritus of psychiatry and behavioral sciences at Ohio State University.
Arnold cited another recent study that found that both boys and girls with ADHD tend to have earlier sexual experiences than those without the disorder.
"It's not only what you would expect, but it's what's already established pretty well," Arnold said. "The symptoms of ADHD set a girl up for early pregnancy."
The new study involved more than 384,000 Swedish women and girls between the ages of 12 and 50 who gave birth between 2007 and 2014. Of those women, about 6,400 had been diagnosed with ADHD.
Teenage births were 6.2 times more likely among women and girls with ADHD, researchers found.
Females with ADHD also were more likely to have risk factors that could harm their pregnancy, including smoking during the third trimester (6.8 times as likely), morbid obesity (two times as likely) and alcohol or drug abuse (20 times as likely).
People with ADHD have trouble keeping their lives organized, which means girls are more likely to forget to carry around condoms or take their birth control pill daily, Arnold explained.
They also are more likely to be impulsive and take risks in their daily lives, Arnold and Skoglund said.
However, it also appears as though doctors, counselors and parents aren't taking ADHD into account when talking safe sex with teen girls, Skoglund and Arnold added.
"Women with ADHD may receive inadequate contraceptive counseling in regards to their underlying difficulties," Skoglund said. "They somehow fail to access - or inadequately respond or act upon -- such counseling."
Contraception is widely available in Sweden, Skoglund said, but that doesn't seem to make a difference for girls with ADHD.
"In contrast to those without a diagnosis, this group doesn't seem to benefit from guidance on contraception and societal interventions targeting the risk for early and unplanned pregnancies that has been very successful in other groups of teens," Skoglund said.
The problem is compounded by the fact that ADHD is under-recognized and underdiagnosed among females, she added.
Skoglund and Arnold said it is very important for parents of an ADHD-diagnosed teen girl to make sure their disorder is being adequately treated.
"In addition, they should make sure that their daughters have sufficient contraception, and intervene to prevent early debut and use of alcohol and illicit drugs," Skoglund said.
Parents might want to consult with the girl's gynecologist about forms of birth control that don't require daily attention, such as a hormone implant or an IUD, Arnold said.