When using oral contraception, it is important to understand the changes that may take place. The hormones in birth control pills can have several effects, one of which may be increased breast size.
The progesterone and oestrogen in contraception pills may cause actual breast tissue growth. This will be a more consistent and unchanging type of growth than oedema-related breast growth experienced while on the pill.
Some pills contain different levels of hormones than others. Oral contraception that has higher hormone levels is more likely to increase breast size.
Oedema, also known as water retention, can also take place. Water retention can take place specifically in the breasts while using contraception pills due to the hormones.
Women who experience enlargement due to oedema may notice only a temporary change in breast size. A decrease in size after using oral contraception for several months is normal.
A monthly decrease in breast size may take place in women who experience oedema-related enlargement. When hormones are withdrawn during the placebo pill phase, water is not being stored, so breasts may decrease in size during this time.