Does gestational diabetes increase breast cancer risk?

This study investigated if there is a link between gestational diabetes and a risk of developing breast cancer.

This study showed that women who developed gestational diabetes in 2 or more pregnancies had an increased risk of developing breast cancer.

Gestational diabetes mellitus (GDM) is a condition that occurs in pregnant women whereby they develop diabetic symptoms. These symptoms include glucose intolerance and insulin resistance which results impaired blood sugar control. In some cases, these symptoms persist after pregnancy, particularly if a woman experiences GDM in multiple pregnancies.

There is evidence to suggest a link between type 2 diabetes and an increased risk of developing breast cancer. The link between GDM and breast cancer is less clear. 

This study included 39,198 women. They were recruited based on a family history of cancer (sister) but were cancer-free upon enrollment. Follow-up was performed at various timepoints and the occurrence of gestational diabetes and breast cancer was reported.

1283 women (3.3%) experienced one GDM pregnancy, 353 women (0.9%) experience 2 or more GDM pregnancies. There was no significant risk of developing breast cancer in women who developed GDM overall. GDM was associated with a 73% increased risk of developing a particular form of cancer called ER-negative breast cancer. This type of breast cancer is not dependent on the hormone estrogen for growth.

Women who experienced multiple GDM pregnancies had a greater risk of developing both total (68%) and invasive (72%) breast cancer.

This study conluded that multiple GDM pregnancies was associated with an increased risk of developing breast cancer. 

These women had a family history of breast cancer (sister). This may influence the risk of breast cancer also. 

If you have any questions regarding gestational diabetes and/or breast cancer then please discuss them with your physician.