"My worry is those girls don't come back half of them pregnant," said Zainab Hawa Bangura told a luncheon at the British Residence in New York.
She was meeting with editors, Tina Brown and the British ambassador to the U.S. in preparation for an unprecedented global summit next week in London on sexual violence in conflict. Angelina Jolie and British Foreign Secretary William Hague will co-chair.
The abduction of more than 300 schoolgirls by Boko Haram militants in April shocked the world and caused outrage among Nigerians. More than 200 girls remain captive.
Bangura said the international community needs to prepare the girls' families for their return and put psychological and other supports in place for the girls.
And she told her audience that more than 2,000 girls in Nigeria already had been abducted before this case brought the situation to the world's attention.
The fate of the schoolgirls is expected to be an intense discussion at next week's summit. Some aid and advocacy groups wonder how any pregnancies from rape in such a high-profile case will affect the wider debate over access to abortion services.
U.S. foreign aid is prohibited by Congress from subsidizing abortions as a method of family planning, but advocacy groups have lobbied the Obama administration, including Secretary of State John Kerry, to issue an executive order saying aid could be used to provide abortions for women raped in conflict.
"It is imperative that during next week's summit, Secretary Kerry and others address post-rape care as part of the larger conversation around sexual violence in conflict," Serra Sippel, President of the Washington-based Center for Health and Gender Equity, said in a statement emailed to The Associated Press.
Bangura, the daughter of a Muslim cleric, was almost married off at the age of 12 in Sierra Leone but became a forceful advocate for women during the deadly conflict there. She said more than 60,000 females were raped during the violence. She said the youngest victim she advocated for was 3 years old.
On Friday, Bangura wove stories of her own background with startling details about her work persuading leaders, often male leaders, to see sexual violence as a serious issue.
She said she won Congo President Joseph Kabila's attention to the issue of sexual violence by members of his military by asking him how he would feel if his twin sister were raped.
But she said that in Somalia, a leading judge there scoffed, "In Somalia, we don't have rape."
A report released this year by her office said there is unprecedented political momentum globally to end conflict-related sexual violence, but more effort is needed at the national level.
Bangura said Friday her office is now looking at 12 priority countries, including Syria, Colombia, Bosnia and Congo.
She has said perpetrators almost never face justice.
The issue of sexual violence goes beyond women, she added.
"Today, almost 10 countries we're looking at have evidence of sexual violence against boys," she said. "In Syria, it's terrible."
Bangura also spoke of the need to fight the stigma of rape, especially in cultures where women might be blamed. In some cases, she said, women give up children born of rape because of the discrimination that follows.
She urged a higher status for women overall.
"If you don't respect your women in times of peace, you can't protect them in times of war," she said.