How Your Breasts Change During Pregnancy

For some women, swollen and very tender breasts are the first clues that they are pregnant: Right from the start, your breasts are preparing for their job of producing milk. Here, Heather Weldon, M.D., an OB-GYN in Vancouver, Wash., answers some of the most common questions about your mammaries during pregnancy.

Pregnant woman asleep

How and when will my breasts change?

Breasts are busiest in the first trimester. During the first few weeks, progesterone causes milk glands to develop and estrogen stimulates growth of the milk ducts. Breasts typically expand one or two bra cup sizes, veins get darker, and nipples get larger, more erect and darker so that eventually, the baby can find them easily.

What happens after the first trimester?

Soreness usually goes away, though the breasts won’t get smaller. As you approach your due date, there may be a little more growth and maybe some leaking of colostrum, the protein- and antibody-rich pre-milk substance that’s “liquid gold” for a newborn.

When do breasts start producing milk?

During pregnancy, rising prolactin levels initiate production, but breasts don’t make real milk because estrogen and progesterone block prolactin receptors. After delivery, those hormone levels fall sharply and oxytocin is released, stimulating milk ducts to contract and deliver milk. The infant’s suckling stimulates nerves that signal the release of prolactin and oxytocin, continuing the demand-supply cycle.

I have really small breasts. Will I be able to nurse my baby?

Breast size is largely determined by the amount of fat present in them. Except for very rare cases, even if you have small breasts, you still have enough milk glands and ducts.

Can I avoid developing stretch marks on my breasts?

Unfortunately, stretch marks are usually genetically predetermined and you can’t do much to prevent them. Moisturizing will make breasts more comfortable as the skin stretches, and time will make the marks less visible.

What if I’ve had breast surgery?

There’s usually no problem if incisions for augmentation were made in the armpit or under breast fold. Nipple incisions, however, sometimes damage nerves that trigger hormone stimulation. Whether you can nurse after reduction surgery depends on how many milk glands and ducts were removed, whether nipples were repositioned and if there’s a clear path for milk to leave the breasts. Either way, it’s worth trying.

Play it safe: Clogged milk ducts cause red, tender, hard lumps and are common during pregnancy. Still, tell your doctor or midwife if you develop one. >>Jeanne Faulkner, R.N., is a freelance writer based in Portland, Ore.

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