We know breasts serve a more important purpose than hypnotizing your partner, but it may help to learn a bit more about why and how they change.As estrogen, progesterone and fat storage increase, so does your breast size. As the milk-producing glands get bigger during pregnancy, you can add up to a pound of tissue, and two cup sizes.

It’s common for your breasts to get sore early in pregnancy. It’s one of the common ways women first realize they’re pregnant. They start to itch as the skin begins to stretch.At the same time, you’ll notice your nipples and surrounding areolas get darker and larger. More veins and bumps begin appearing in the area. Biologically, this happens as your blood volume increases during pregnancy.

Evolutionarily, this happens for a different reason. Newborns need high contrast to make sure their mouths hit their targets. More prominent, dark nipples direct the baby to his or her vital food source—you.That’s another big breast change you’ll experience. You may feel like a 1940s faucet—leaky. A small amount of pre-milk leaking (called colostrum), can start as early at the end of the second trimester. Major leaking generally occurs after giving birth.

You’ll also develop Montgomery’s tubercles: small, harmless bumps on your areolas. These bumps secrete a lubricant that discourages bacteria growth—a reason not to wash your nipples with soap. The lubricant will also help prevent your nipples from cracking during breast-feeding.

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