July 12 (UPI) -- Women who receive fertility treatments are not at a heightened risk of ovarian, womb or breast cancer, according to large study in Britain.
Researchers at University College London studied 255,786 women between 1991 and 2010 and found a small increased risk of non-invasive breast and ovarian tumors but concluded they are not from the assisted reproductive therapies. Instead they are linked to underlying characteristics of women already at higher risk.
Their findings were published Wednesday in the British Medical Journal.
In assisted reproductive technology, which includes in vitro fertilization, women are exposed to high levels of hormones, which can carry an increased risk of breast, womb and ovarian cancers.
The researchers noted that previous studies on risks of reproductive cancers in women who underwent fertility treatments have been inconsistent.
"This is by far the largest study and represents good news for women and couples considering assisted reproductive technology or those who have already had ART," Dr. Alastair Sutcliffe, of the UCL Great Ormond Street Institute of Child Health, said in a press release.
They used records from the Human Fertilization and Embryology Authority, identifying all women who had assisted reproduction in Britain. They then linked this information to national cancer records.
The women were followed up over an average of 8.8 years. The average age at first treatment was 34.5 years and women had an average of 1.8 treatment cycles.
Cause of infertility involved at least one female factor -- endometriosis -- in 44 percent of women. Infertility was unexplained in 19 percent of women and 33 percent were because male factors, such as low sperm count.
Compared with the general population, they found no overall increased risk of breast cancer or invasive breast cancer associated with assisted reproduction.
An increased risk of non-invasive breast cancer was found in 1.7 cases per 100,000 person years and it was associated with an increasing number of treatment cycles.
Ovarian cancer increased risk -- invasive tumors and borderline ones -- had an absolute excess risk of 5 cases per 100,000 person years.
"While we found a small increased in ovarian cancer, this was not due to the ART treatment, but part of the underlying characteristics of those women already at higher risk," Sutcliffe said.
In addition, the researchers found no overall increased risk of womb cancer.