(CNN) Seng Moon was an impoverished refugee in an internal displaced person (IDP) camp in northeastern Myanmar when her sister-in-law convinced her to cross the border into China to find a job.

She passed out on the car journey after being given a travel sickness pill. When Seng Moon awoke her hands were tied behind her back. Her sister-in-law was gone and she was alone with a Chinese family.

After several months, Seng Moon's sister-in-law returned and told her she was to be married to a Chinese man.

Seng Moon was moved to another house, where she was tied up and locked in a room. Her new "husband" would bring her meals, after which he would rape her.

This went on for two months, until Seng Moon was dragged from the room and finally introduced to the man who had been abusing her for weeks.

She says the man's father told her this was her husband, and advised them to build a family.

In this picture taken on May 13, 2018, internally displaced people and local villagers attend a church service in Myitkyina, Kachin state.

The abuse and the rape continued, and eventually Seng Moon became pregnant. After she gave birth to a baby boy, she asked to go home to Myanmar.

Moon says her husband said she was free to go -- but that she couldn't take her baby.

Seng Moon's experience is one of dozens of stories of women trafficked from Myanmar's Kachin State into China documented in a Human Rights Watch (HRW) report , titled "Give Us a Baby and We'll Let You Go."

The unusual thing about Seng Moon, the rights group said, is that she managed to escape with her child, thanks to the assistance of another trafficker.

Most women who return have to leave their children in China.

Bought to make babies

Demand for Kachin women is driven by the continued effects of China's "one child" policy and decades of often illegal sex-selection, which led to a dearth of women in many parts of the country, according to HRW.

The gender disparity is particularly pronounced in rural areas, where many young people leave for work in cities and men who remain struggle to find wives.

According to the report traffickers can make between $3,000 and $13,000 selling women to Chinese families.

For the most part, the buyers of these women are not looking for wives, but merely a woman to give birth to their children, often created by raping them repeatedly until they become pregnant, the report claims.

"Once trafficked women and girls gave birth to a baby, they were sometimes able to escape their captors, but usually at the cost of leaving their child behind with little hope of seeing the child again," the report said.

"Back in Myanmar, survivors grapple with trauma and stigma as they try to rebuild their lives."

This issue has been ongoing for years, the report alleges, fueled in part by the large amounts of impoverished women displaced by years of war and conflict which continues in many parts of eastern Myanmar.

"Myanmar and Chinese authorities are looking away while unscrupulous traffickers are selling Kachin women and girls into captivity and unspeakable abuse," Heather Barr, acting women's rights co-director at Human Rights Watch, said in a statement.

Without jobs or many prospects in Myanmar, as well as poor or non-existent legal protections in many IDP camps, the women are easy prey for traffickers.

"The Myanmar and Chinese governments, as well as the Kachin Independence Organization, should be doing much more to prevent trafficking, recover and assist victims, and prosecute traffickers," Barr said.

"Donors and international organizations should support the local groups that are doing the hard work that governments won't to rescue trafficked women and girls and help them recover."

Residents of the Jan Mai Kawng Internal Displacement Camp, which is sponsored by the Kachin Baptist Church walk past a church on the camps property on June 7, 2014 in Myitkyina, Myanmar.

Trafficked and abused

HRW interviewed 37 trafficking survivors over a three-year period. While some were convinced by strangers to travel to China, many were trafficked by relatives or friends lured by the potential big payout. One woman -- trafficked while she was still a teenager -- told HRW that the broker who sold her to a Chinese man was her aunt.

When they make it to China, the women were often subjected to horrific abuse, which did not necessarily stop when they became pregnant.

"They fed us sometimes, but not always," one survivor told HRW.

"The original broker had gone, and a second broker came and showed me to the men and asked me which one I liked. When I said I didn't like any of the men, the broker slapped me. This continued for a few days and I kept refusing. Then the broker raped me. The broker got mad -- to calm himself down at night he raped me. It was a violent rape. When I didn't take off my clothes he beat me."

Many of the men appeared to be familiar with the practice, seeing the women as dispensable.

"Normally, after Myanmar girls in China have a baby they go home -- maybe you're like this," one survivor recounted her "husband" telling her. He said that when their baby was 1-year-old, she could return to Myanmar, but the child would stay with him.

Those who do return, do so to a place with little resources or facilities to support them. Women who have been through horrific abuse and trauma are unable to seek counseling, and some face stigma from their fellow IDPs due to the rape they experienced.

"Most victims face terrible situations. They come back, and they are totally different from us," a Kachin Women's Association official told HRW. "They are just gazing, staring ... People who just came back don't even dare to go outside and show their faces ...They feel guilty for being (trafficked)."

HRW has called on the Myanmar and Kachin governments to do more to protect women from traffickers and crack down on the trade in women, as well as to raise awareness of the potential risks of being trafficked in IDP camps, and provide resources for survivors.

Authorities in Myanmar and China did not respond to HRW about the group's concerns. CNN has reached out to China's Ministry of Foreign Affairs and Myanmar's Ministry of Border Affairs for comment.