Birth control pills may increase a person’s breast size because they contain the hormones estrogen and progestin. However, the effect is usually temporary and the breasts may return to their original size over time.
The two primary hormones present in most types of birth control pill are:
- estrogen, a female sex hormone
- progestin, a synthetic version of progesterone, which is another female sex hormone
The body produces estrogen and progesterone. During the menstrual cycle, levels fluctuate, and this can cause a change in breast tissue.
When a person starts taking the birth control pill, their levels of these hormones rise, and this can result in an increase in breast size.
However, the size of the breasts may return to normal after a few monthly cycles or after a person stops taking the pill.
Birth control pills can increase the size of a person’s breasts.
Estrogen and progesterone levels change during the menstrual cycle, and this can cause changes in the breast tissue. A person may feel that their breasts are tender or sore, as a result.
Many birth control pills contain the same hormones, estrogen and progestin, which is a synthetic form of progesterone. Starting to take the pill can stimulate the breasts to grow. However, any increase in size is typically slight.
Within a few months of taking the pill, the breasts generally return to their regular size. This usually also happens if a person stops taking the pill.
There is another link between the birth control pill and breast enlargement. When a person starts taking birth control, the changes to hormone levels can cause the body to retain fluid. This can make the breasts feel engorged.
When fluid retention, or edema, is responsible for breasts that feel bigger, a person may notice that their breast size returns to normal during the week that they are not taking an active pill. During this week, they will get a period.
Weight gain is a side effect of many birth control pills. Like the possible increase in breast size, any associated weight gain is typically slight.
In 2014, researchers published a review of 49 trials. They had tried to find a causal link between weight gain and types of birth control that contained both estrogen and progestin. The researchers found that these pills tended to have no significant impact on weight.
If a person who starts taking the birth control pill does experience minor weight gain, it is because hormonal changes have caused the body to retain fluid.
In general, doctors consider the pill to be safe. However, a person should be aware of some possible side effects, which include:
- changes in mood
- changes in menstruation, involving either more or less bleeding
- tenderness in the breasts
The increase in hormones, particularly estrogen, can also cause more serious side effects. Birth control pills that only contain progestin are less likely to cause these effects.
Serious, though rare, side effects of birth control include:
Before starting or changing a method of birth control, discuss the risks with a doctor.
A person must see a doctor before they can start taking the birth control pill and before switching pills.
It is essential for each person to discuss the potential side effects and risk factors with a medical professional.
Some risk factors to consider include:
- being overweight or obese
- being over the age of 35
- having a history of migraines with auras
- having a history of high blood pressure
- the presence of a clotting disorder
- having high cholesterol
If a person has any of these risk factors, a doctor may recommend a different type of birth control. The doctor should be able to provide additional options.
When taking a birth control pill, a person should be aware of the potential risks and side effects.
One of the milder side effects is a slight, temporary increase in breast size. Though rare, some other side effects are more severe, and they can even be life-threatening.
Before a person starts using hormone-based birth control, it is essential to discuss the advantages and disadvantages with a doctor.