Childhood cancer survivors were previously told they would be unable to become pregnant later in life. However, new research found that most can conceive, though it might take longer than usual.

Female cancer survivors were 48 percent more likely to report infertility than their sisters who did not have cancer, with the biggest difference in risk seen in the youngest survivors and siblings, according to a study published online on Monday in The Lancet Oncology.

However, nearly two-thirds or 64 percent of the infertile survivors eventually did get pregnant. The study noted that cancer survivors had compromised uterine function and reduced ovarian reserve, which impact fertility.  Ovarian reserve measures the existing amount of eggs in a woman's ovaries.  Egg supply and proper performance of the uterus are critical for reproductive success.

"The main message counters what some people have thought, which is if you had cancer you won't be able to get pregnant or have children," said Dr. Lisa Diller, the study's senior author, from the Dana-Farber/Boston Children's Cancer and Blood Disorders Center.

For the study, Diller and her colleagues used data from questionnaires in an ongoing study of 3,531 cancer survivors and 1,366 of their sisters between the ages of 18 and 39 years old.

The study noted that the survivors were all diagnosed before age 21 with cancer at one of 26 medical centers in the U.S. or Canada from 1970 through 1986. The women had all been cancer free for at least five years.

"We do not have data about why providers did not prescribe infertility drugs, but are concerned about a provider bias against treating cancer survivors for infertility," said study leader Dr. Sara Barton, according to Medical News Today.

"Perhaps providers assessed the chance of success as poor and therefore decided not to attempt therapy, or perhaps survivors were less motivated to take drugs after previous extensive treatment. Alternatively, reproductive medicine providers might have been uncomfortable with perceived medical comorbidities."