RANKL and OPG and their influence on breast volume changes during pregnancy in healthy women

Objectives:

Breast cancer risk is influenced both by number of pregnancies and breastfeeding duration, but not all women benefit similarly from these. Breast volume changes during pregnancy may be predictive for later transformation of the breast. This study investigated the influence of serum RANKL and OPG at the start of pregnancy on breast volume changes.

Methods:

In the Clinical Gravidity Association Trial and Evaluation (CGATE) program, pregnant women were followed prospectively from gestational week 12 to birth. Three-dimensional breast surface imaging and volume assessments were performed. Serum RANKL and OPG were measured at study entry before gestational week 12. A linear regression model including breast volume at the start of pregnancy, RANKL, OPG, and other factors was used to predict breast volume at term.

Results:

The mean breast volume was 413 mL at the start of pregnancy, increasing by a mean of 99 mL up to term. In addition to body mass index and breast volume at the start of pregnancy, RANKL and OPG also appeared to influence volume (P= 0.04 and P= 0.07, respectively). Women with measurable RANKL values had a mean volume increase 32 mL larger than in women without measurable RANKL. The presence of OPG reduced the mean volume change by 27 mL.

Conclusions:

This is the first study showing that RANKL and OPG influence breast volume changes during pregnancy. Understanding the molecular mechanisms behind the effects of pregnancy on the breast might help in developing strategies for mimicking pregnancy effects in order to reduce breast cancer risk.