University of Western Australia researchers followed women treated for breast cancer who waited to conceive and women who did not.
They found that conceiving as early as six months after diagnosis did not appear to reduce survival among women with localized disease and a good prognosis.
"As long as a woman understands her prognosis, and that prognosis is good, there is no need to wait," researcher Angela Ives tells WebMD. "But it is very important that she discuss pregnancy with her doctor before making the decision."
Study after study has shown pregnancy to be safe for breast cancer survivors with a good prognosis. Some even suggest a protective benefit for conception and childbirth.
But the timing of pregnancy following breast cancer treatment has not been well studied. Women are often told to wait several years before conceiving, primarily to deter women with a poor prognosis from attempting pregnancy.
Ives and colleagues examined pregnancy timing and survival among 123 women between the ages of 15 and 44 who had at least one pregnancy following a diagnosis of breast cancer. The women's average age at first-postdiagnosis pregnancy was 35.
Half of the women conceived within two years of their breast cancer diagnosis.
Compared with young cancer survivors who did not become pregnant, those who conceived six months or more after being diagnosed appeared to have a slight survival advantage. But this advantage probably doesn't mean that pregnancy has a direct impact on survival.
Rather, the thinking is that women who are healthiest after breast cancer treatment are more likely to attempt pregnancy than women who are sickest.
The 'healthy-mother effect' hypothesis was first proposed more than a decade ago by researchers in Finland who found childbirth after breast cancer treatment to be strongly linked to survival.
"I don't think that anyone believes that pregnancy, with its huge surge in hormones, would be in any way directly protective against breast cancer," says Eugenia Calle, PhD, of the American Cancer Society. "It is much more likely that women who feel better are more likely to conceive or attempt conception."
Study 'Too Small'
Calle tells WebMD that she knows of no formal guidelines instructing breast cancer survivors to delay pregnancy for at least two years after diagnosis or treatment.
But she adds that the Australian study was far too small to prove that attempting pregnancy earlier than this is safe.
Just 20 of the patients in the study got pregnant within six months of diagnosis, and these women had much poorer outcomes than women who waited longer than six months. Forty-two patients got pregnant within seven to 24 months of diagnosis, and 61 got pregnant after two years.
"This study was just too small to answer the question that these researchers claim to have answered," she says.
SOURCES: Ives, A. BMJ Online, Dec. 8, 2006. Angela Ives, researcher, University of Western Australia. American Journal of Obstetrics and Gynecology, March 1994; vol 170: pp 818-823. Eugenia Calle, PhD, managing director of analytic epidemiology, American Cancer Society.
By Salynn Boyles
Reviewed by Louise Chang