There are breast changes during pregnancy you should expect almost from day one. Blame the hormones. As hormone levels increase, so does blood flow and fluid retention causing your breasts to feel swollen, sore and sensitive to touch. In fact, breast tenderness can be one of the early signs of pregnancy.

Why do boobs get bigger during pregnancy?

Estrogen stimulates growth of the breast duct cells and generates the secretion of prolactin, another hormone. Prolactin stimulates breast enlargement and milk production. Progesterone supports the formation and growth of milk-producing cells within the glands of the breasts.

How soon do your breast change when pregnant?

Starting around 6 to 8 weeks, you may notice your breasts getting bigger, and they'll continue to grow throughout your pregnancy. It's common to go up a cup size or two, especially if it's your first baby. Your breasts may feel itchy as the skin stretches, and you may develop stretch marks on them.