Patients had their ovaries frozen before cancer treatment began. And their own ovarian tissue was then re-implanted once they were well.
Ten women went on to have successful pregnancies.
UK experts say the results should prompt more doctors to offer this service.
In one of the most comprehensive studies of its kind, Danish women had whole or part of an ovary removed and frozen in the hope this would protect them from powerful anti-cancer drugs.
Though ovary freezing and transplantation is available in the UK, it is not common - partly because of concerns that transplants could carry cancerous cells.
But researcher Dr Annette Jensen said her team`s study, published in the journal Human Reproduction, is reassuring.
She added: "As far as we know this is the largest series of ovarian tissue transplantation performed worldwide and these findings show that grafted ovarian tissue is effective in restoring ovarian function in a safe and effective manner.
"The fact that cancer survivors are now able to have a child of their own is an immense, quality-of-life boost for them."
Prof Adam Balen, spokesman for the Royal College of Obstetricians and Gynaecologists, agreed the study added further reassurance that ovarian transplantation carried little risk of containing cells that might cause cancer to return.
He added: "While egg freezing is more commonly available in the UK, ovarian freezing may on occasion be the better option.
"This is a great study. It should prompt people in the UK to provide the service more frequently."
The study showed transplants could also prove beneficial in other circumstances unrelated to pregnancy - for example helping hormone levels to return to normal.
But researchers cautioned that despite promising results the procedure is still at an early stage and longer-term studies are needed.
More about:
