Women Having Multiple Babies after IVF at 44 Percent Higher Risk of Developing Breast Cancer

Women who give to multiple babies after IVF have greater risk of developing breast cancer than women who give birth to a single child or remain childless, according to a new study from Netherlands.

The data for the study came from 19,861 women who received IVF or ICSI treatment between 1983 and 1995. In the study group, 1688 women gave birth to multiples (13%) while 6027 (48 percent) had singletons and 4874 (39 percent) had no babies. Researchers found that women who had multiples were at a 44 percent greater chance of developing breast cancer than women with singleton delivery or no children.

Also, only multiple pregnancies after complete implantation of all embryos had the elevated risk of breast cancer and not the pregnancies with incomplete implantation. Scientists said that this difference is due to the alteration in key hormonal levels. The study findings supported  a hypothesis, which says that there is a link between high embryo implantation potential and breast cancer risk.

"It has been generally assumed that increased levels of estrogen and progesterone in multiple pregnancies stimulate cellular proliferation in the breast, which increases accumulation of somatic mutations during cell division and leads to the development of breast cancer," Dr Els Groeneveld from the VU University Medical Centre of Amsterdam, the Netherlands said in a news release

"Thus, breast cancer could be seen as a consequence of the multiple pregnancy itself. However, we also hypothesise that an additional maternal trait might be associated with an increased breast cancer risk in these women," Dr Groeneveld added.

According to researchers, these women might have a trait that increases their odds of developing breast cancer, such as maternal serum concentrations of vascular endothelial growth factor (VEGF).

VEGF is a protein associated with the growth of breast cancer. Dr Groeneveld and team had recently found that women with high VEGF have improved embryo implantation potential.

The study will be presented at the European Society of Human Reproduction and Embryology.

Other research teams have found no elevated cancer risk among women who had undergone IVF. A recent study from Israel also found no additional risk of either breast cancer or any other cancer in these women.

Breast cancer is one of the most common cancers diagnosed in women in the U.S. Despite its high prevalence, researchers aren't sure why normal breast cells turn cancerous. Most experts say that breast cancer is caused by a combination of genetic, hormonal and environmental factors.  According to estimates by the National Cancer Institute, 232,340 new cases of female breast cancer will be diagnosed in 2013 in the U.S and nearly 40,000 women will die due to breast cancer.