One in 16 American women were either forced or coerced into their first sexual encounter, according to a study investigating the long-term negative impacts of such "trauma" on women's health.
In the US, "the #MeToo movement has highlighted how frequently women experience sexual violence," the researchers wrote in the introduction.
"However, to date, no recent studies have assessed the prevalence of forced sex during girls' and women's first sexual encounter or its health consequences."
Published on Monday in the American Medical Association's peer-reviewed journal (JAMA Internal Medicine), the study is based on a sample of more than 13 000 women aged 18 to 44, who were interviewed as part of a survey conducted between 2011 and 2017 by the Centres for Disease Control and Prevention (CDC).
About 6.5% of women were either forced or coerced into their first sexual encounter. Extrapolated out to account for the US population (327 million), this number works out to approximately 3.3 million women in that age group, the authors note.
That equals one in 16 women.
The women surveyed said they were submitted to multiple forms of coercion: 56.4% said they experienced verbal pressure, 46.3% said they were held down, 25.1% were physically harmed, 22% were forced to consume alcohol or a drug, and 16% said their partners threatened to end the relationship.
Forced "sexual initiation," the study said, was reported by women of all ethnicities and socioeconomic backgrounds.
There is a higher risk for black women, women who were born outside the US, low-income women and women with lower levels of education.
The main difference between women who consented to their first sexual encounter and those who were coerced is linked to age: on average, women who were coerced were closer to 15 years old, while women who consented were 17 years old.
For women who had been coerced, their male partners were also much older -- 27 years old, versus 21 years old in couples where the woman had consented.
The study also showed that "forced sexual initiation appeared to be associated with multiple adverse reproductive, gynecologic and general health outcomes."
Women who had been physically restrained during their first sexual encounter were subsequently more likely than women who consented to have unwanted pregnancies or abortions.
They were also more likely to develop endometriosis, pelvic inflammatory disease or problems with ovulating or menstruation.
Their general health was also worse, with a higher likelihood of drug use and mental health issues, the researchers said, adding that their research points to a need for public health strategies to prevent sexual violence.
The study never used the word "rape", although some of the situations addressed in the study seem to meet the criminal definition of the term.